Essential Tools for Every Refrigeration Technician: A Comprehensive Review
Are you intrigued by the inner workings of refrigeration systems and the vital role they play in our everyday lives? Whether you’re an aspiring refrigeration technician or a seasoned pro, understanding the tools of the trade is essential.
In this comprehensive review, we delve into the top tools that every refrigeration mechanic should have in their arsenal. These tools are not mere conveniences; they are the very instruments that empower technicians to diagnose, repair, and maintain refrigeration systems efficiently and effectively.
1. Manifold Gauge Set: Refrigeration mechanics rely on manifold gauge sets to simultaneously measure high and low side pressures in refrigeration systems. These sets are like the eyes of the technician, providing critical insights into the system’s condition. By providing real-time data, refrigerant gauges are essential for diagnosing issues and ensuring optimal system performance.
2. Vacuum Pump: A vacuum pump may seem unassuming, but its role is monumental. It evacuates air and moisture from refrigeration systems before the introduction of refrigerant, ensuring that the system operates efficiently without unwanted contaminants.
3. Leak Detection Tools: Finding elusive refrigerant leaks is a challenge without the right tools. Leak detection tools, including electronic detectors and bubble solutions, play a crucial role in environmental protection and system efficiency by pinpointing these leaks.
4. Digital Multimeter: An HVACR technician’s electrical diagnostic prowess relies heavily on a digital multimeter. This tool measures voltage, current, and resistance in electrical components, making it indispensable for troubleshooting electrical issues.
5. Pipe Cutters and Flaring Tools: Copper pipes are the lifeblood of many refrigeration systems, and pipe cutters and flaring tools ensure these essential components are accurately cut and shaped for the job.
6. Pipe Benders: The importance of smooth, kink-free bends in copper pipes cannot be overstated. Pipe benders are the secret to achieving these precise bends without compromising the integrity of the pipe.
7. Thermometers and Thermocouples: When it comes to temperature measurement, accuracy is key. Thermometers and thermocouples help technicians monitor temperatures at various points in the system, assisting in both diagnostics and cooling optimization.
8. Tubing Tools: Properly preparing tubing for installation is a fundamental step in any refrigeration project. Tubing tools, such as deburrers and reamers, ensure that tubing is ready for action.
9. Hex Key Set: Hexagonal screws and bolts are commonplace in refrigeration systems. A set of hex keys is a technician’s trusty companion for swiftly disassembling and reassembling components.
10. Oil Pump and Oil Injector: Lubricating oil is the lifeblood of compressors. Oil pumps and injectors ensure that the compressor functions optimally by delivering the right amount of lubrication.
11. Torque Wrench: Precision matters in refrigeration systems. Torque wrenches guarantee that bolts and nuts are tightened to precise specifications, safeguarding components and maintaining proper seals.
12. Digital Scale: In the intricate world of refrigeration, precision is paramount. This is where a digital scale steps in as a silent but indispensable partner for refrigeration mechanics. Why? Because refrigerants, lubricants, and various chemicals must be added to systems with meticulous accuracy.
A digital scale ensures that the right quantities are added, helping maintain the system’s efficiency, performance, and, perhaps most importantly, the environment. It’s not just about getting the job done; it’s about getting it done right, and that’s where the digital scale shines. So, let’s weigh in on the importance of this often-overlooked tool in the refrigeration technician’s toolkit.
These tools are the cornerstone of any refrigeration technician’s toolkit. Stay tuned as we dive deeper into each of these essential instruments, unveiling the art and science behind their usage, and why they’re indispensable for refrigeration technicians around the globe.
In this article we’ll answer a question that we get all the time. What filter, if any, can filter out the SARS-CoV-2 virus which leads to COVID-19, the disease? We’ll show you how efficient the different air filters are at filtering out various items for asthma and allergy sufferers, and the virus that leads to COVID-19.
If you prefer to watch the Video of this presentation, then scroll to the bottom or click on the following link. Air Filters vs COVID-19
The ability of an air filter to remove microorganism, dust, pollen, dust mites, mold spores, pet dander, bacteria and viruses is indicated by a numerical value. This number, which is indicated as a MERV rating, states the filter’s efficiency at removing various sizes of these items. We’ll show you which filters, if any, work the best to protect you from these potentially harmful organisms.
MERV Rating
Minimum Efficiency Reporting Values, or MERVs, indicate the filter’s ability to capture larger particles, those 0.3 microns and larger. The higher the numerical rating, the greater the air filter is at removing particles from the air stream. A MERV-13 is better than a MERV-11 filter at removing particles, but how good are they against bacteria and a very small virus that leads to COVID-19.
Virus and Bacteria Removal
According to ASHRAE, research has shown that the particle size of the SARS-CoV-2 virus that leads to COVID-19 is around 0.1 microns. This is much smaller than what may be picked up by these air filters. As this chart shows, the virus lives in the invisible region, while others like dust, cat dander and human hair are visible to the human eye.
Sizes of various items shown in Microns. Invisible items in black area on chart, including the SARS-CoV-2 Virus.
Luckily, the SARS-CoV-2 virus doesn’t travel through the air own its own. It rides on respiratory droplets and droplet nuclei (dried respiratory droplets) that are predominately 1 micron in size and larger. These filters have various efficiencies at capturing the viruses that are in the 1-to-3-micron range according to ASHRAE.
The SARS-CoV-2 virus riding a respiratory droplet in the 1 to 3 micron range
ASHRAE
As the chart shows, ASHRAE recommends using a minimum of a MERV 13 filter, which is at least 85% efficient at capturing particles in the 1 to 3-micron size range. A MERV 14 filter is at least 90% efficient at capturing those same particles. High-efficiency particulate air (HEPA) filters are even more efficient at filtering human-generated infectious aerosols.
MERV Rating and Air Filter Efficiency for Particle sizes 1 to 3 microns in size
By definition, a HEPA air filter must be at least 99.97% efficient at capturing particles 0.3 micron in size. This 0.3-micron particle approximates the most penetrating particle size (MPPS) through the filter. HEPA filters are even more efficient at capturing particles larger AND smaller than the MPPS. Thus, HEPA air filters are more than 99.97% efficient at capturing airborne viral particles associated with SARS-CoV-2 which leads to COVID-19.
HEPA filters can capture and trap microorganisms, including viruses and bacteria, helping to reduce the risk of respiratory infections. So, if possible, use the highest MERV rated air filter with your system, or get a portable HEPA air filter for your room or office. HEPA filters are the most efficient at capturing small microorganisms like the SARS-CoV-2 virus.
Where are HEPA Filters used?
HEPA air filters are used in residential, commercial, and industrial facilities. In homes there are portable types that can be moved from room to room, and others that can be installed in a central air conditioning system serving the whole house.
HEPA air filters are also used along with ULPA filters in cleanrooms, labs, and other spaces requiring a very clean environment.
Asthma and Allergy Management
For individuals with asthma, HEPA filters help reduce asthma triggers like airborne irritants and respiratory allergens. According to the Asthma and Allergy Foundation of America (AAFA), nearly 26 million people have asthma in the United States. There are 4.8 million children under the age of 18, and nearly 21 million adults suffering from asthma. On average, 10 people in the unites States die every day from asthma. A total of 3,517 deaths in 2021.
According to the AAFA over 100 million people each year in the United States experience various types of allergies. Allergies are the sixth leading cause of chronic illness in the U.S. HEPA filters are highly effective at removing allergens such as pollen, dust mites, and pet dander, providing relief to allergy sufferers.
Editorial Process:
Some of the links in this article may be affiliate links, which can provide compensation to the MEPAcademy at no cost to you if you decide to purchase. Our reviews and articles are made by an industry professional experienced in the engineering and construction of commercial buildings.
Are you paying too much for your HVAC equipment? How do you know if the quote you received for your equipment is a fair price? Do you have a method of comparing what you have paid for various HVAC equipment with what is being quoted currently?
Keeping track of the cost of HVAC Equipment allows you to quickly provide budgets and check the cost of equipment before you purchase. This database allows you to easily keep track of the most common HVAC equipment.
HVAC Equipment Cost Database
Using an HVAC Equipment cost database will save you a lot of money by avoiding the costly mistake of paying too much for equipment.
Air Conditioners in Historical Pricing HVAC Equipment Database
The HVAC Equipment Cost database keeps track of all your equipment quotes or purchases for easy reference and parametric checks, such as cost per ton ($/Ton), cost per CFM ($/CFM)
For an HVAC Piping Estimators the need for quick budgets for the installation of piping is best handled with a spreadsheet of different material types and sizes. Having an estimating software program can make this process a lot easier, as the material pricing is always up to date and can be entered into the spreadsheet quickly. You can get a copy of this spreadsheet to help you price piping fast and efficiently.
HVAC Piping Unit Pricing Calculator
HVAC PIPING UNIT PRICING
Often the requirements of the RFP or bidding instructions will call for the price per foot to install piping beyond that which is required by the contract drawings. Such pricing maybe used for change-orders. Having these numbers available and updated often also gives you a quick reference for budgeting projects. It’s good to know when doing job site comparisons of different piping options or during discussions with engineering, what the cost is for the various piping sizes and types of materials.
HVAC Piping Unit Pricing Calculator for Copper and Carbon Steel from 1/2″ to 14″
COST PER FOOT
The cost per foot for the installation of piping needs to include fittings and hangers prorated into the value. It’s best to look at a standard length of pipe and then figure that you will have a Tee and 90 degree elbow in that length.
So for example, using twenty feet of copper water pipe with a Tee and 90 degree elbow plus the hangers to build a unit price would represent a field condition of a fitting every ten feet.
For higher density projects like Hospitals you could put more fittings in your unit pricing. Total those cost up and then divide by 20 to derive at a cost per foot for that particular size and material type.
20 feet of pipe + 2 Fittings + 3 Hangers / 20 = Cost per Foot
If the piping is insulated, you can also put the values in for insulation.
The Estimating Wizard provides two spreadsheets for tracking unit pricing, one for HVAC Piping and the other for Plumbing piping. Get a copy and start tracking your cost per foot, or be prepared to give a quick budget based on your knowledge from your spreadsheet of unit prices. Watch the video below to see how quick and easy it is to track the cost per foot for various sizes and material types.
MEP Academy HVAC Piping Unit Pricing Spreadsheet
The MEP Academy provides a spreadsheet that makes calculating unit pricing simple. The spreadsheet is available by following this link, HVAC Piping Unit Pricing Spreadsheet
HVAC Piping Unit Pricing Calculator Example
In the screenshot above there is a place for you to build your hanger requirements (#1), and a place to put your tax rate and hourly labor rate (#2).
For each size of pipe and material type you would insert the unit cost for Material (#3) and Labor (#4).
Under item (#5) you would build your typical run of pipe and enter the quantity of fittings you might expect for the type of building and system. You would add whatever you think will be required for every so many feet of pipe. In the example above we are showing that for every 20 feet of pipe you will have 1 Elbow and 1 Reducing Tee.
Under item (#6) you would add the cost per lineal foot for insulation if required. You could also look at insulation as a separate value and leave the pipe bare.
Line item (#7) is where you indicate the hanger spacing, and for each hanger you defined under item (#1) you will get the quantity as defined by the linear feet in item (#5) divided by your hanger spacing, which will affect your cost.
Line item (#8) is the calculated cost per linear foot of piping for that size and material type of pipe.
Summary Sheet
After you have all your unit pricing information inputted into the spreadsheet, all you have to do to get a budget for installing piping is to enter the quantity of piping (#9) for each size and material type (#10). The system will automatically calculate the cost (#11) to install that run of piping based on your unit pricing data. The total cost will be shown at the top of the spreadsheet (#12).
The proper sizing and layout of condensate drain lines is important for the protection of property and for the proper functioning of the air conditioning equipment.
If you prefer to watch our YouTube version of this presentation, scroll to the bottom.
Condensate Drain Pipe Sizing
The size required for the condensate pipe is dictated by the local code. Enclosed you will find the requirements for many local codes, but be sure to check your code for your local requirements. If the outlet size of the equipment’s condensate drain is larger than what’s shown in this chart then your required to use the larger outlet size.
Minimum Condensate Drain Pipe Sizing Chart
Slope to be at least 1/8” per foot or 1 percent, that is for every 12” horizontally there must be at least an 1/8” drop vertically.
Condensate drain piping to slope a minimum of 1/8″ per every 12″ horizontal
Attics or Furred Spaces
If the Air Conditioner is suspended above an inaccessible ceiling, such as a gypsum board ceiling or attic space then you will need to provide a means for protecting the building elements from the overflow of the primary drain and for indicating that there is a leak.
Also, drain pans that are poorly drained can cause water to stay in the pan risking the possibility of algae and bacteria growth. Below are some possible solutions, but as always check your local code for the approved method.
Option 1 – Secondary drain pan with drain piping. This would hang below the Air Conditioning unit in case the A/C units primary pan overflowed. Also, there is a requirement to provide secondary drain piping to a point of termination that would provide notification to the occupants that there is a leak, such as terminating above a window or doorway.
Option 1 – Secondary drain pan with piping terminating in observable location
Option 2 – An additional drain pipe connection that sits above the primary drain connection and whereby the secondary drain piping terminates in a location to alert the occupants of the clogged primary drain.
Option 2 – Secondary drain piping connection to primary drain pan
Option 3 – Leak detection device that automatically shuts down the Air Conditioner if the primary drain becomes clogged.
Option 3 – Primary drain with leak detection device
Option 4 – Secondary drain pan with leak detection, located beneath the coil that shuts down the unit upon a leak.
Option 4 – Secondary drain pan with leak detection
The additional drain pan or drain pan connection shall be provided with a drain pipe that will determinate in an observable area, such as in front a window or above a doorway, and be of a size not less than 3/4”. Secondary drain pan shall not be less than 1-1/2” in height and extend 3” wider on each side of the coil or AC unit.
Secondary drain piping terminating above window. Pipe doesn’t have to be visible as shown.
Drain Termination
Where can and can’t you terminate the air conditioners condensate drain piping? There are several options where you can terminate the condensate drain line;
Indirect Drain
Condensate Pump to Indirect Drain
Drywell
Leach pits
Landscaped areas that are properly designed to handle the volume of condensate
To Properly designed stormwater treatment systems.
Indirect Drain
Lavatory tailpiece in the same tenant space as the air conditioner
Laundry standpipe
Janitors Sink
Inlet of Bathtub Overflow – Must be accessible
Collect and send to cooling tower (See description below)
Cooling Coil condensate to sink tailpiece.
The connection to a plumbing fixtures tailpiece has to be made within the same tenant space as the air conditioner cooling coil that is generating the condensate.
Drywell
A drywell can be used for the termination of your air conditioners condensate drain. Check your local code for the specifics, but generally it includes some or all of the following depending on whether it’s for residential or a commercial project:
A minimum size hole, such as 2 foot by 2 foot by 3 feet deep, or a round hole such as 12” diameter by 3 feet deep.
A minimum of 6” of soil or concrete shall provide cover above the rocks
Some form of barrier between the soil and the top of the drywell where the rock begins, such as building paper or plastic
Drywell to be filled with gravel or crushed rock, often with a stated minimum size rock such as 1 inch diameter
The termination of the condensate drain pipe shall connect indirectly to the drywell drain pipe.
The drywell drain pipe to be a minimum of 1-1/2” PVC or other approved material.
Drywell to be at least three feet away from the building structure or any footings.
Drywall for Air Conditioner Cooling Coil Condensate
There are various methods of providing drywells depending on the local code. There are prefabricated drywells that can be used and ones that are made by using a large diameter piece of PVC pipe or similar material.
Some codes will require you to collect the condensate from cooling coil drain pans and return it to the cooling tower if the equipment is served by a cooling tower and the total combined capacity of the HVAC cooling coils exceeds a certain amount like 65,000 btu/hr.
This is a water conservation measure, and there are some exceptions to this requirement, such as if the total capacity of the AC Equipment cooling coils are less than 10% of the total capacity of the cooling tower, or if the location of those AC Cooling coils are in a remote location, far from the tower.
Some locations where you can’t terminate condensate;
Public ways
Sidewalks
Driveways
Alleys
No termination of condensate on public area ways
Excluded from Code Requirements
Excluded from these codes are non-condensing type of equipment like radiant cooling panels that are designed to prevent condensate from occurring by keeping the temperature of the chilled water above the dew point temperature/vapor pressure of the surrounding air. These are system designed to operate in sensible cooling only modes.
Piping Material
The material types that can be used for condensate drain piping varies by jurisdiction but the most commonly cited materials are:
Copper
PVC – DWV
CPVC
ABS – DWV
Polyethylene
Galvanized steel
Cast iron.
Also the use of short radius 90-degree elbows are often prohibited. You can normally use standard fittings until you reach a certain size at which point you might be required to use drainage pattern fittings (DWV)
Traps
Traps are to be installed as required per the manufactures recommendation. No traps are required on the secondary drain pan, this is to allow immediate notification that the primary drain has failed.
Cleanouts
Cleanouts are required in case of plugged drain pipes. Provide as required to prevent the need to cut drain pipes for unplugging. Some of the following maybe used for cleanouts if approved by your local code authority;
Plugged tees
Union connections
Short clamped hoses at the unit (see image above)
When you have more than one air conditioning unit condensate tied to a main condensate pipe, then every change of direction shall have some method of cleanout. Check your local code as this maybe a requirement for even a single air conditioners condensate piping.
Condensate Pumps
Condensate pumps can be used to elevate the condensate vertically to a point where it will then discharge into a code approved gravity sloping condensate drain line. The condensate pump should be interlocked with the Air Conditioning Unit to prevent its operations if the condensate pump is inoperable.
Please remember that code requirements are always changing, so check for the most current code in your area at the time of design and installation. Or ask an inspector for the current installation practice.
Having an MEP Academy Estimating Spreadsheet that automates portions of your estimates, will save you valuable time that could be used to make more sales. All aspects of the cost of furnishing and installing an HVAC and/or a Plumbing system is contained in one spreadsheet made specifically for the MEP industry. For plumbing only see below.
For a Plumbing only Spreadsheet, use this Commercial & Residential Version. Plumbing Only. For a simple Residential HVAC & Plumbing Spreadsheet. Residential version.
Dashboard
The Main Dashboard provides you with all the information you need to make a quick decision on whether to make further adjustments, or if one of the metrics looks out of place based on historical data. The Dashboard gives you a quick overview of all that is going on within the Estimating Spreadsheet.
Estimating Dashboard within the MEP Academy Estimating Spreadsheet
Your MEP Academy Estimating Spreadsheet needs to be able to handle rental equipment, general conditions, subcontractors, piping and plumbing takeoffs, sheet metal, labor rate tables with crew mix capabilities, , and a bid summary. Each sheet in the estimating spreadsheet automatically calculates the values you enter, showing you a new total bid amount.
Will cover portions of the MEP AcademyEstimating Spreadsheet starting at the back of the Excel spreadsheet and working our way toward the front summary page last.
Choose your crew mix based on the level of experience and the different pay scales based on each project. Pick any combination and quantity of tradesman based on the requirements of the project.
Labor Rates and Crew Size within the MEP Academy Estimating Spreadsheet
There is a separate crew labor rate for HVAC Piping Shop & Field, Sheet Metal Shop & Field, and Plumbing.
Enter the project equipment price and labor to rig the HVAC and Plumbing equipment into place. Compare supplier pricing easily side by side. The MEP Academy Estimating Spreadsheet automatically selects the lowest bidder but lets you override that decision.
HVAC Equipment page within the Estimating SpreadsheetHVAC & Plumbing Equipment Sheets
Do you need a jobsite trailer or onsite management? Enter the quantity and level of the staff required to run the project, whether one person or dozens. Set the quantity and duration of each general condition, along with the rate. General Conditions is broken down into three sections as follows: #1 – Management, #2 – Construction Office (Non-Reoccurring Expenses), and #3 – Construction Office (Reoccurring Expenses).
HVAC & Plumbing contractors often subcontract out for Air & Water Balance, Sheet Metal & Piping Insulation, Water Treatment, Building Automation, Excavation and other specialty trades that they don’t self-perform. This spreadsheet was made especially for the HVAC & Plumbing contractor and their most often used subcontractors.
For those contractors that do plumbing the following Plumbing Fixture sheet will give you a place to record your vendors quotes and the labor it takes to install each type of fixture. What is also revealed is the overall cost per fixture.
Plumbing Fixtures page within the Estimating Spreadsheet
Each trade has a specialty sheet for those items that aren’t considered equipment or a fixture, but for which there is a cost impact. The MEP Academy Estimating Spreadsheet includes Sheet Metal, HVAC Piping & Plumbing Specialty sheets.
HVAC and Plumbing Specialty Pages within the Estimating SpreadsheetSpecialty Sheets in Estimate Spreadsheet
Material & Labor Summary Sheets
You will find a Sheet Metal, HVAC Piping & Plumbing material & labor summary sheets where all of the other specialty sheets are summarized for your review and last minute edits. Each sheet will be divided between field & shop fabrication work. The first section covers the field installation items.
Sheet Metal Material and Labor Summary – Estimating Spreadsheet
Each of the field labor summary sheets contain a row to add for the following
Material Handling
Consumables
Punch List
Cleanup
Detailing
Supervision
Shop Fabrication Summary Section
For those of you that have a fabrication shop, there is a section to add material and labor.
Shop Fabrication Summary
Rentals
For those HVAC air conditioning and Plumbing projects that require a crane, fork lift, scissor lift or any other equipment that you don’t own but will be required on the project. Having a spreadsheet that maintains a list of the most common equipment you normally rent along with their rental rate will save you time and money while avoiding having to call for pricing on every job.
Rental Sheet in Estimating Spreadsheet
Engineering
If you do your own design then you should have a sheet of each of the personnel responsible for spending time on the engineering task. If you’re doing design/build work, but don’t do the engineering yourself, but hire a third party, then you should add some engineering review time. It’s your responsibility to manage your third-party engineer to make sure they design within your cost parameters.
All of your estimates are summarized on the last tab of the MEP Academy Estimating Spreadsheet for easy review. You can quickly scan each of the categories to see where all the project cost has shown up. There is the labor and material summary for HVAC Sheet Metal, HVAC Piping, and Plumbing and another section for Subcontractors, General Conditions, Rentals, etc.
Estimating Spreadsheet Summary PageMEP Academy Estimating Spreadsheet Summary
The MEP Academy Estimating Spreadsheet contains a bid risk assessment form that rates the success of winning any particular project that you are contemplating pursuing. The risk assessment form will help you determine if the project is worth bidding based on a set of questions that rate your answers.
Bid Risk Assessment
The answers to these questions will give you a score from which you can use to see how the project rates on a scale of risk and reward. The total risk assessment score will also inform you which level of approval is required within your company depending on how you rate your risk values as the example shown below. The total score is 25, which according to this contractor would require the Vice President to sign-off on the project or approve the decision to pursue bidding on the project.
The MEP Academy Estimating Spreadsheet is used to gather all the information for estimating a project, putting it into a format where you can make quick adjustments and decisions while the spreadsheet gives you an immediate update on the price.
Purchase this spreadsheet at its currently reduced price of ONLY $245.00, which usually sells for $599.00
Watch the YouTube video below to see the MEP Academy Estimating Spreadsheet in action.
In this article, we break down two essential smoke control strategies designed for large commercial spaces. First, we cover a targeted smoke control method tailored for hotel guestroom floors, keeping hallways and exit routes safe during an emergency. Then, we explore how an atrium smoke control system works to keep open, multi-story spaces clear of smoke by using smoke exhaust fans. These are just a couple of the many approaches used to manage smoke effectively and maintain safe evacuation paths.
Hotel Zoned Smoke Control System
A Highrise hotel can use a zoned smoke control pressurization system to keep smoke from spreading across guestroom floors during a fire, ensuring that hallways, stairwells, and elevators remain safe for occupants to evacuate. Here’s how the system typically works:
Dedicated Smoke Exhaust System for Hotel Guestroom Floors
When smoke is detected on a guestroom floor, the smoke control system activates automatically. In a dedicated smoke control system, the equipment is only used for smoke control and will require frequent testing.
The supply fans pressurize areas critical for evacuation, such as stairwells, elevators, and corridors, by pumping in fresh air. This pressurization creates a pressure differential between these escape routes and the potentially smoke-filled spaces, which forces smoke back into the affected areas and prevents it from entering escape paths.
The Sandwich Technique
The sandwich technique is a zone smoke control method used in high-rise buildings to contain smoke to the fire floor and prevent vertical spread. It works by exhausting smoke directly from the fire floor while pressurizing the floors immediately above and below with supply fans, creating a pressure “sandwich.” This differential pressure keeps smoke isolated to the fire floor, ensuring that adjacent floors remain smoke-free.
The floor above and below the fire zone is positively pressurized, while the floor with the fire is under negative pressure created by the smoke exhaust fan. There are smoke control dampers on each of the supply and exhaust ducts that are opened or closed depending on the floor or fire zone. The exhaust damper is opened only on the fire floor, and the supply dampers are opened on the floor above and below the fire floor. This is just one strategy. By venting smoke directly from these spaces, the system reduces smoke density at the fire source and improves visibility for both occupants and emergency responders.
This is a dedicated system where the smoke control equipment is used only during emergency and is not part of the regular HVAC system.
Stairwell Pressurization
Most building codes will require that the stairwell in a high rise be pressurized to keep the smoke out. This allows the occupants a safe egress out of the building without having to breathe in smoke. A dedicated fan system supplies clean air into stairwells, creating a pressure differential that prevents smoke infiltration. The pressurization created by the fan must be significant enough to prevent smoke from entering the stairwell but also allow occupants to open the stairwell door.
In a high-rise, a vestibule is often used for smoke control with stairwells or elevator lobbies, to act as a buffer zone between areas with different pressures. These enclosed spaces are pressurized with fresh air during a fire to prevent smoke from entering, ensuring that stairwells and elevator shafts remain safe for evacuation and firefighter access.
Non-dedicated Smoke Control System
Here is how a non-dedicated smoke control system in a high-rise hotel using existing HVAC air handlers that supply and return air on each guestroom floor during normal operation, with each floor designated as a separate fire zone:
Using an Air Handler (HVAC System) in a Smoke Control System
Upon fire alarm activation on any guestroom floor, the smoke control system engages, signaling the HVAC air handler for the affected floor to switch to smoke control mode. The dampers in the air handler switch to smoke control by shutting the return damper and opening the outside air damper. The air handler serving the fire floor closes the supply air damper on that floor to prevent spreading the fire to other areas. The supply dampers on the floors above and below the fire floor open to pressurize and sandwich the fire floor to prevent smoke infiltration.
The exhaust air damper on the fire floor opens, while the exhaust dampers on all other floors close. This will create a negative pressure on the fire floor preventing smoke from exiting the floor. The smoke will be exhausted out the air handler or in this setup a smoke exhaust fan is provided.
The HVAC air handler on the floors directly above and below the fire floor activate in pressurization mode, supplying fresh air to create a positive pressure barrier.
This pressurization prevents smoke from migrating vertically, confining it to the fire floor. Stairwells, corridors, and elevator shafts are pressurized separately to keep them free of smoke, allowing safe evacuation routes for occupants and access for firefighters.
Atrium Smoke Control
When a fire ignites, it begins to consume nearby materials, releasing heat, smoke, and toxic gases. The combustion process produces high temperatures, causing hot air to rise. Flames reach upward, creating a vertical plume of heat and smoke above the fire source. The intensity and spread of the fire depend on fuel type, oxygen availability, and surrounding materials.
Atrium Smoke Exhaust System
The rising heat from the fire generates a vertical column of smoke and hot gases known as the smoke plume. This plume carries particulates, toxic gases, and intense heat toward the ceiling. As the plume rises, it pulls in the surrounding air, growing in size and cooling slightly. The plume’s upward motion spreads smoke and heat vertically, reaching ceiling levels quickly, especially in tall spaces.
A smoke control system for an atrium is specifically designed to manage and exhaust smoke from the large, open space of an atrium during a fire. Atriums are common in modern commercial and institutional buildings like hotels, shopping malls, and office complexes, where they provide open, multi-story gathering spaces that are visually appealing. However, their large volume and vertical open design present unique challenges for smoke control, as smoke can accumulate and spread quickly throughout multiple levels. A well-designed atrium smoke control system prevents smoke buildup, enhances visibility for evacuation, and keeps pathways clear for firefighters.
Ceiling Jet Stream
Upon reaching the ceiling, the hot smoke and gases spread outward, forming a layer just below the ceiling, this is called the ceiling jet. The ceiling jet moves horizontally, carrying intense heat and smoke across the ceiling surface.
When the ceiling jets hits the wall, it turns back thickening the smoke layer. This jet is key to triggering fire detection systems, as smoke detectors and sprinklers respond to the elevated temperatures in this layer. The ceiling jet influences the spread of heat and smoke to other areas and guides smoke control strategies.
Smoke Layer
As the ceiling jet spreads, smoke accumulates, forming a hot, dense smoke layer beneath the ceiling. This smoke layer thickens as the fire burns, moving downward over time and reducing visibility in the space. The smoke layer is hazardous, containing toxic gases and reducing breathable air near floor levels as it descends. Smoke control systems aim to slow or halt the smoke layer’s spread to maintain visibility, protect egress paths, and aid firefighting efforts. The international building code section 909.8.1 states that the lowest horizontal surface of the smoke layer must be maintained at 6 feet (1829 mm) above any walking surfaces that is part of an egress within a smoke zone.
Make-Up Air System
To ensure the smoke exhaust system works effectively, a make-up air supply is often required to replace the air that’s being expelled. Make-up air helps maintain proper airflow and prevents negative pressure that could disrupt smoke control. This air supply can be introduced from adjacent zones, louvers, or through dedicated air intakes positioned lower in the atrium.
The make-up air system is designed to ensure that fresh air enters the space below the smoke layer, reducing the chance that smoke will be pulled downwards, which could impede evacuation and visibility.
What is Plug holing
In smoke control systems, plug holing is a phenomenon where cool air enters and mixes with the hot smoke layer near an exhaust vent, disrupting the effective removal of smoke. Instead of drawing out hot smoke from the upper layer, the exhaust fan begins to pull in the cooler, denser air from below. This reduces the efficiency of the smoke exhaust system, as it allows smoke to accumulate rather than being fully vented out.
Plug Holing causes problems for Smoke Exhaust Systems
Plug holing is particularly problematic in high atriums or large spaces, where temperature differences between the smoke layer and ambient air can cause this mixing. To prevent plug holing, smoke control systems may use carefully designed exhaust vent placements, larger vent sizes, or specific airflow controls to ensure that only the smoke layer is removed, maintaining clear and safe evacuation paths.
Stratification
Stratification occurs when a layer of warm air forms just below the roof due to solar heating. This layer can interfere with smoke detection and smoke layer behavior.
Stratified Layer Interferes with Smoke Layer
When the sun heats the roof, the air beneath it warms up and creates a thermal barrier. This warm air layer remains at the ceiling level, preventing cooler air and smoke from rising naturally.
In HVAC water-based systems, water distribution is critical to ensure that each terminal unit receives the correct amount of heated or cooled water. Two popular piping configurations, Direct Return and Reverse Return, are often used in these systems. Each configuration has its unique benefits, potential drawbacks, and implications for water balancing and system performance. Here, we’ll break down the differences between these two types of piping layouts, discuss their impact on water balancing, and examine the pros and cons of each.
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What is Direct Return Piping?
In a Direct Return Piping system, water flows to each air handler coil and returns along the shortest path. This means that the closes air handlers coil to the heating or cooling supply source, such as a boiler or chiller, will have the shortest overall piping length, while the furthest air handler will have the longest piping route.
Direct Return Piping
Since the closes air handlers have less piping, they’ll have less pressure drop, considering the pressure drop for all coils are the same. This creates different pressure drops for the piping circuits to and from each air handler, which creates a water balancing issue. This is why balancing valves are often added to create additional pressure drops to equal out each piping circuit.
Direct Return is often considered simpler and more cost-effective to install, as it requires less pipe and can be laid out with fewer complex fittings.
The layout can differ with all coils in a straight line like this piping diagram which makes it easier to see just how this works. If the pump is cycled on and the water flows through the system, the water molecules leaving the chiller at the same time will reach each air handler coil at different times. If you must run 50 feet and your competition must run 100 feet, you will easily return to the finish line first. The closest coils will get fed first, while the farthest coil will receive chilled or heated water last.
What is Reverse Return Piping?
In a Reverse Return Piping system, water flows to each terminal unit via the shortest path but returns along the longest path. Essentially, the return pipework is designed so that the last unit on the supply line is the first to return to the source. This approach results in equalized pipe lengths for each terminal unit, which is one of the defining characteristics of Reverse Return piping.
Reverse return piping
The theory is that each air handler will have the same distance from the source and back which would make their pressure drops equal and balancing valves not required. In theory maybe, but air handler zone differences can affect the pressure drop through each coil as each control valve adjust flow for their current zone demand.
Here we can see that all the water leaving the chiller will return from each air handler to the chiller at approximately the same time as the total round trip piping length is the same distance.
Here is another look at a reverse return where the air handlers are set in a straight line with equal lengths of pipe from the chiller to the coil and back to the chiller. The water for each air handler arrives at different times, but the total length is the same overall, which balances out the pressure drop in a perfect world.
We can see that with the direct return piping layout the water returns to the source much quicker that the reverse return piping layout. The reverse return piping distance for the water to travel is much longer than the direct return method.
Piping Differences
In a Direct Return system, the main pipes remain the same size along the entire supply and return runs until they reach a section where the flow decreases, and a size reduction is needed. This is simpler compared to a Reverse Return system, where the design often requires a gradual reduction in pipe size along the return path as flow is picked up from each terminal unit. This consistency in sizing throughout most of the Direct Return system reduces complexity and makes both material handling and installation faster and easier.
Here are the main ideas to remember about Direct Return vs. Reverse Return piping systems:
Direct return vs reverse return piping
Direct Return Piping
Simpler Installation: Main pipes stay the same size until a reduction is necessary, streamlining material handling and installation.
Shorter Total Pipe Length: Typically requires less piping, saving on material costs and installation time.
Imbalance in Flow: The unequal pipe lengths to each terminal unit create varying flow resistances, making water balancing more challenging.
Higher Maintenance: More frequent adjustments and use of balancing valves are needed to ensure consistent flow rates.
Lower Initial Cost: Installation is generally less expensive due to reduced pipe material and labor.
Reverse Return Piping
Naturally Balanced Flow: The design ensures equal pipe lengths to and from each terminal unit, aiding in consistent flow and easier balancing.
Higher Installation Cost: More piping material and complex routing increase initial costs and installation time.
Longer Total Pipe Length: Requires additional piping to loop back the return path, impacting space and cost.
Reduced Maintenance: Less need for frequent adjustments due to the self-balancing nature of the system.
These points highlight the trade-offs between the simpler, cost-effective Direct Return and the more balanced but costlier Reverse Return systems.
In this article we’re diving into one of the most popular topics in modern sanitization UV-C light and how it works to fight germs, bacteria, and viruses. UV-C technology is gaining a lot of attention for its ability to disinfect homes, businesses, and even industrial spaces, but with all this interest comes plenty of questions.
In this article, we’ll be answering some of the most frequently asked questions about UV-C sanitizers. Can you safely use UV-C light in your home? Is it effective against viruses like COVID-19? How do you know if a UV-C device is working properly, and what should you look for when choosing one?
Can I use UV-C lights while I’m in the room?
In most cases, it is not safe to be in the room when a UV-C light is in operation, as direct exposure to UV-C rays can harm your skin and eyes. Many devices come with safety features, such as motion detectors that turn off the light when someone enters the room. If you’re using Far UV-C (200 to 230 nanometer), this can be safe for occupied rooms, but standard UV-C lights should only be used in unoccupied spaces.
Portable Shielded UV-C Light Air Purifier
A portable shielded air purifier with an internal UV light won’t kill germs that are on surfaces within the room as the light is shielded. This type of air purifier pulls air into the housing where it’s exposed to the UV light that kills the germs as they pass through. This type of shielded UV light can be used when the room is occupied. If you want full room coverage, you’ll need to use an open lamp type that requires that the room is unoccupied when in use.
Shielded Portable UV-C Light Air Sanitizer
Open Lamp UV-C Light
This open lamp UV Light has a timer that can be set for 15, 30, or 60 minutes of run time. It will beep for 15 seconds to allow the person to exit the room. This type of open UV lamp will shine in a 360-degree radius effectively sanitizing the area within its reach. You want to set this in the middle of the room if possible and leave the room while the light is on. You don’t want anyone looking at the light while it’s on as this can damage their eyes.
Avoid looking at the UV-C light which can damage your eyes.
Hospitals and Healthcare Facilities. UV light systems are installed in operating rooms, patient rooms, and high-touch surfaces to prevent the spread of infectious diseases. Portable UV sanitizers are also used to disinfect medical equipment and tools, providing an extra layer of protection against hospital-acquired infections.
Portable UV-C Light sterilizing an unoccupied Operating Room in a Hospital
Food and Beverage Processing. UV-C light is used to sterilize surfaces, packaging materials, and even air in food processing plants. It helps prevent contamination and ensures food safety, commonly applied in meat, dairy, and beverage industries.
HVAC Systems in Buildings. UV lights are installed in HVAC ducts and air handling units to disinfect the air by killing airborne bacteria, viruses, and mold spores. This improves indoor air quality in large commercial buildings, such as offices, hotels, hospitals, and schools.
How does UV-C light work to kill germs?
UV-C light works by emitting ultraviolet light at a specific wavelength (typically 254 nanmeter) that penetrates the cell walls of microorganisms, such as bacteria, viruses, and mold. This light damages their DNA or RNA, which prevents them from reproducing or functioning, effectively killing or inactivating the germs. UV-C lights can inhibit the growth of mold or mildew on cooling coils, ducts, and other moist surfaces in HVAC systems reducing unpleasant odors. This can be useful for people with allergies, asthma, or other respiratory conditions.
Can UV-C light kill Gems? Yes
Is UV-C light safe for humans, pets, and plants?
Direct exposure to UV-C light is not safe for humans, pets, or plants. It can cause skin burns and eye injuries, such as photokeratitis (like sunburn of the cornea). However, certain forms of UV-C, like Far UV-C (200 to 230 nanometer), are considered safer for occupied spaces. Most UV-C devices should only be used in unoccupied areas or enclosed systems to avoid exposure.
A person should not look directly at UV-C light, as it can cause serious damage to the eyes and skin. UV-C light is harmful because it emits high-energy ultraviolet radiation.
How long does it take for UV-C light to disinfect a room or surface?
The time required depends on the power of the UV-C light, the size of the room or surface, and the specific microorganisms being targeted. On average, it can take anywhere from 10 to 60 minutes to disinfect a room or surface. Manufacturers usually provide recommended exposure times based on their devices’ specifications and the area being disinfected.
What types of pathogens can UV-C light kill?
It is effective against a wide range of microorganisms, including bacteria (coli, MRSA), viruses(influenza, SARS CoV-2), mold, and fungi. It is also commonly used to control airborne pathogens and allergens in HVAC systems and surfaces.
Is UV-C effective against COVID-19?
Yes, UV-C light has been shown to be effective at inactivating the SARS CoV-2 virus, which causes COVID-19. Studies have confirmed that UV-C light can destroy the virus by breaking down its RNA, making it unable to replicate. However, it should be used as part of a comprehensive strategy that includes proper ventilation, cleaning, and other precautions.
Can UV-C light penetrate through surfaces or fabrics?
No, UV-C light does not penetrate through solid surfaces or opaque materials like fabrics, glass, plastic, or metal. It only disinfects what it directly shines on. This means that any objects or areas that are shaded or blocked from the light will not be disinfected.
What is the difference between UV-A, UV-B, and UV-C light?
UV-A (315 to 400 nanometer) and UV-B (280 to 315 nanometer) are longer wavelength forms of ultraviolet light that primarily cause skin aging, sunburns, and DNA damage leading to skin cancer. These are present in sunlight.
UV light Spectrum
UV-C (200 to 280 nanometer) has the shortest wavelength and is the most effective for germicidal purposes because it can inactivate pathogens. Unlike UV-A and UV-B, UV-C is filtered out by the Earth’s atmosphere, so it’s not naturally present in sunlight.
Only UV-C is commonly used for disinfection.
How do I know if a UV-C light is working properly?
Some UV-C devices include indicator lights or built-in sensors that show whether the UV-C lamp is functioning. Since UV-C light is invisible to the human eye, you can’t see it. Regular maintenance, such as cleaning the lamp and replacing bulbs when necessary, will ensure proper functioning. You can also use UV intensity meters to measure the output of the light.
What’s the lifespan of a UV light bulb?
The UV light bulbs typically last between 9,000 and 12,000 hours, depending on the manufacturer and usage conditions. However, even though the bulbs may still light up after this period, their germicidal effectiveness diminishes over time, so it’s recommended to replace them after reaching their rated hours.
Are there any risks of UV-C light damaging materials or electronics?
Prolonged exposure to UV-C light can cause some materials to degrade over time, especially plastics, rubber, and certain fabrics. UV-C light can cause discoloration, brittleness, or weakening of these materials. However, properly installed and used UV-C devices do not typically cause harm to electronics.
Do I need to clean surfaces after using UV-C light?
UV-C light does not leave any residue, so there’s no need to clean surfaces after use. However, UV-C light only disinfects surfaces, so if there is visible dirt or grime, cleaning is necessary before disinfection, as UV-C does not penetrate dirt or organic matter effectively.
How much area can a UV-C sanitizer light cover?
The coverage area depends on the power of the UV-C device and its design. Most devices specify the maximum area they can effectively sanitize. Smaller units may only cover a few square feet, while larger units can disinfect entire rooms or HVAC systems. For general reference, high-powered UV-C units can cover areas of up to several hundred square feet.
The physical area that the UV-C device can effectively disinfect, is often expressed in square feet or cubic feet. Larger spaces require more powerful or multiple UV-C devices to ensure full coverage. Compare devices based on the size of the area they can disinfect effectively, especially if you’re considering them for larger rooms, air ducts, or water systems.
Are UV-C sanitizers portable and easy to install?
Yes, many UV-C sanitizers are portable and designed for easy installation. Portable units are often plug-and-play, allowing you to move them between rooms as needed. Some devices, such as those used in HVAC systems or mounted for air or surface disinfection, may require professional installation.
Is UV-C light energy-efficient?
UV-C lights are relatively energy-efficient, especially when used for shorter disinfection cycles. Most UV-C devices have low power consumption compared to the energy required for constant air filtration or chemical disinfection methods. Devices typically range from 10 to 200 watts, depending on their size and capacity.
Does UV-C light affect air quality or release harmful chemicals?
Properly designed UV-C devices do not release harmful chemicals or fumes. However, some UV-C lamps can produce a small amount of ozone, especially if they emit wavelengths below 240 nanometers. Ozone can be harmful in high concentrations, so it’s important to choose ozone-free UV-C lamps or ensure proper ventilation in the space.
Can UV-C light replace traditional cleaning methods?
No, UV-C light should not completely replace traditional cleaning methods. It is most effective when used as a supplement to cleaning. For example, you should still clean surfaces to remove dirt and debris before using UV-C to disinfect. Similarly, combining UV-C with good ventilation and air filtration enhances overall disinfection.
These answers provide a comprehensive overview of the most common questions about UV-C sanitizer lights.
In this article we’ll cover ASHRAE Standard 62.1 which outlines the ventilation requirements for acceptable indoor air quality (IAQ) in commercial and institutional buildings. The standard uses a combination of the Ventilation Rate Procedure (VRP), which calculates the amount of outdoor air needed based on space type, occupancy, and area.
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ASHRAE 62.1 Minimum Ventilation Air Requirements
The ASHRAE 62.1 ventilation rate formula is based on three key factors. the number of people in the space, the square footage of the area, and the zone air distribution effectiveness (Ez). The number of people determines the amount of fresh air needed for occupants, while the square footage accounts for the ventilation required to offset contaminants from the building materials and activities. The zone air distribution effectiveness adjusts the airflow based on how well the ventilation system distributes air within the space, ensuring optimal air quality.
Let’s go through three examples using an office, retail store and classroom to illustrate how the ASHRAE 62.1 ventilation rate calculation works in different spaces.
Example 1. Office Space
Office Ventilation Air Calculation
Given Data.
Occupancy Type. Office space
Floor Area. 5,000 square feet
Occupancy Density. 5 people per 1,000 square feet (as per ASHRAE 62.1 Table)
Outdoor Air Rate per Person. 5 CFM per person
Outdoor Air Rate per Area. 0.06 CFM per square feet
Step 1. Calculate the total number of occupants.
Number of occupants equals Floor Area Occupancy Density. This equals 5,000 square feet divided by 1,000 square feet, multiplied by 5 people per 1,000 square feet equals 25 people.
Calculation for Number of occupants per ASHRAE 62.1
Step 2. Calculate the ventilation rate required for occupants.
Ventilation Rate (People) equals Number of Occupants times Outdoor Air Rate per Person. The Ventilation Rate equals 25 people times 5 CFM per person equals 125 CFM for the people.
Calculation for Ventilation Air required for people in an Office
Step 3. Calculate the ventilation rate required for the area.
Ventilation Rate (Area) equals Floor Area times Outdoor Air Rate. This equals 5,000 square feet times 0.06 CFM per square feet equals 300 CFM for the area.
Calculation for the ventilation Air required for the Area of an Office
Step 4. Total ventilation rate calculation using ASHRAE’s additive method.
Total Ventilation Rate equals (Ventilation Rate for the People) plus (Ventilation Rate for the Area). The Total Ventilation Rate equals 125 CFM for the people plus 300 CFM for the area, for a total of 425 CFM.
Therefore, for this office space, the required outdoor air ventilation rate is 425 CFM.
What we haven’t covered is how the layout of the supply and return grilles affect the amount of ventilation air required. We’ll cover this at the end of this article.
Example 2. Retail Store
Retail store ventilation air calculation
Given Data.
Occupancy Type. Retail store
Floor Area. 10,000 square feet
Occupancy Density. 15 people per 1,000 square feet (as per ASHRAE 62.1)
Outdoor Air Rate per Person. 7.5 CFM per person
Outdoor Air Rate per Area. 0.12 CFM per square feet
Step 1. Calculate the total number of occupants.
Number of Occupants equals Floor Area Occupancy Density. This equals 10,000 square feet divided by 1,000 square feet, multiplied by 15 people per 1,000 square feet equals 150 people
Step 2. Calculate the ventilation rate required for occupants.
Ventilation Rate (People) equals Number of Occupants times Outdoor Air Rate per Person. The Ventilation Rate equals 150 people times 7.5 CFM per person, for a total of 1,125 CFM for the people.
Step 3. Calculate the ventilation rate required for the area.
Ventilation Rate (Area) equals Floor Area times Outdoor Air Rate. This equals 10,000 square feet times 0.12 CFM per square feet, for a Total of 1,200 CFM for the area.
Step 4. Total ventilation rate calculation.
Total Ventilation Rate equals (Ventilation Rate for the People) plus (Ventilation Rate for the Area). The Total Ventilation Rate equals 1,125 CFM for the people plus 1,200 CFM for the area, for a total of 2,325 CFM
Therefore, for this retail store, the required outdoor air ventilation rate is 2,325 CFM.
Example 3. Classroom
Classroom Ventilation Air calculation
Given Data
Occupancy Type. Classroom
Floor Area. 1,200 square feet
Occupancy Density. 35 people per 1,000 square feet
Outdoor Air Rate per Person. 10 CFM per person
Outdoor Air Rate per Area. 0.12 CFM per square feet
Step 1 Calculate the total number of occupants.
Number of Occupants equals Floor Area Occupancy Density. This equals 1,200 square feet divided by 1,000 square feet, multiplied by 35 people per 1,000 square feet, for a total of 42 people
Step 2 Calculate the ventilation rate required for occupants.
Ventilation Rate (People) equals Number of Occupants times Outdoor Air Rate per Person. the Ventilation Rate equals 42 people times 10 CFM per person, for a total of 420 CFM for the people.
Step 3 Calculate the ventilation rate required for the area.
Ventilation Rate (Area) equals Floor Area times Outdoor Air Rate. This equals 1,200 square feet times 0.12 CFM per square feet, for a total of 144 CFM for the area.
Step 4 Total ventilation rate calculation.
Total Ventilation Rate equals (Ventilation Rate for the People) plus (Ventilation Rate for the Area) Total Ventilation Rate equals 420 CFM for the people, plus 144 CFM for the area, for a total of 564 CFM
For this classroom, the required outdoor air ventilation rate is 564 CFM.
The Zone Air Distribution Effectiveness (Ez)
Zone Air Distribution Effectiveness (Ez) is a factor used in ASHRAE 62.1 to account for how efficiently an HVAC system delivers and mixes outdoor air within a given space or zone. It reflects how well the ventilation air is distributed to the occupants’ breathing zone, impacting the amount of fresh air needed for adequate ventilation. The effectiveness varies based on how the air is supplied and returned within the space, considering factors like supply air temperature and system design.
Zone Air Distribution Effectiveness
How Air Distribution Effectiveness Ez Varies
1. Floor Supply, Floor Return, Heating Mode
When warm air is supplied from the floor and mixed into the space, it can be pulled downward and distribute evenly within the breathing zone, leading to a higher effectiveness. ASHRAE indicates a 1.0 Ez for floor supplied and returned warm air. The 1.0 doesn’t add or subtract any CFM from the previous calculations.
Zone Air Distribution Effectiveness
2. Floor Supply, Ceiling Return, Heating Mode
When warm air is supplied from the floor and mixed into the space, it tends to rise and may not reach occupants in the lower part of the room effectively and may not distribute evenly within the breathing zone, leading to a lower effectiveness. ASHRAE indicates a 0.7 Ez for floor supplied and ceiling returned warm air. The 0.7 will add CFM to our previous calculations. For example, our office space was calculated to be 425 cfm. Taking into consideration that the air distribution effectiveness is 0.7, the new CFM would be calculated to be 425 divided by 0.7 equals 607 CFM
Floor Supply of Warm Air and Ceiling Return
Key Factors Influencing Air Distribution Effectiveness
Supply air temperature vs. room air temperature. Larger temperature differences can reduce the effectiveness.
Supply and return air locations. Proper placement of supply and return ducts can improve Ez.
Ventilation system type. Systems like displacement ventilation or underfloor air distribution (UFAD) often have higher effectiveness due to better air mixing.
In general, the higher the Ez value, the more effective the ventilation system is in distributing air, which allows for less outdoor air to achieve the same indoor air quality, making the system more efficient.
This was a simplified explanation of the basic ventilation calculation, as there are a few other key considerations that can change the total CFM required.
Key Considerations
Diversity Factor. In some cases, ASHRAE 62.1 allows the use of a diversity factor to account for spaces that aren’t fully occupied all the time.
System Ventilation Efficiency. Depending on the distribution system (100% Outdoor Air, Multi-zone recirculating, or VAV systems), system ventilation efficiency (Ev) must be factored in to adjust the total outdoor airflow.
These examples show how ventilation rates are calculated based on both the number of occupants and the size of the space, ensuring adequate indoor air quality per ASHRAE 62.1.
How to Calculate Ventilation Air in accordance with ASHRAE 62.1
