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Why is my Air Conditioner not Cooling

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Why My Air Conditioner is not Cooling

Why is my Air Conditioner not Cooling? There are many things that can cause your air conditioner to underperform when you need it most. Here are a few things to check before calling your local air conditioning company unless you prefer a professional to do this. 

If you prefer to watch the YouTube version this presentation, then scroll to the bottom or click this link Why is my Air Conditioner not Cooling

Dirty Filters

One of the most common reason for less cooling is clogged filters. You should replace your filters seasonally or more frequently depending on the usage of your air conditioner. Dirty filters will reduce the air flow to the rooms, causing a loss in cooling.

Replace Dirty Air Filters Seasonally or Based on Usage
Replace Dirty Air Filters Seasonally or Based on Usage

Dirty Coils

The condenser unit sits outside exposed to the elements, including wind, rain, snow, dust, and dirt to name a few. It’s important that the condenser coil be cleaned to allow for proper heat rejection. A dirty coil will reduce the cooling capacity of the system. 

Split System Condenser with Dirty Coil
Split System Condenser

The indoor evaporator coil should also be checked but is less exposed than the condenser coil. The evaporator coil should be mostly protected by a properly maintained filter. When cleaning the coil be sure to clean the drain pan of any dirt and debris and to ensure nothing is blocking the drain piping leaving the drain pan.

Circuit Breaker has Tripped

It may be possible that the system has tripped your circuit breaker. This would stop all electricity from reaching your air conditioner. The indoor and outdoor units should be indicated on the electrical panel. See if the breaker for either of them has been tripped. The position of the breaker will be slightly different than the rest if the breaker has been tripped.

Checked for Tripped Circuit Breakers
Checked for Tripped Circuit Breakers

Disconnect Switch

Located near the outdoor unit will be a little box that has a means of shutting off the power to the unit for service. When any service is being done on the outdoor unit the technician will make sure this is shutoff to prevent an electrical shock. See if the disconnect switch is in the on position, if not then the unit is not getting electrical power.

Leaking Air Ducts

When replacing air conditioners, it would be a good time to check the condition of the ductwork that carries the air throughout the building. Leaks in ductwork should be fixed, as any leak is a loss of cooling capacity and a waste of energy.

Fix Leaking Ductwork. Make Sure all Joints and Seams are sealed.
Fix Leaking Ductwork. Make Sure all Joints and Seams are sealed.

It’s like carry a bag of quarters from the bank and having a hole in the bag, where quarters fall out unnoticed. Seal any leaks to ensure that the energy you are using is only used for cooling the space and not the attic or outdoors. Fixing ducts that leak is one of the greatest energy saving strategies.

Air Flow Obstructions

Make sure that the outdoor condenser section doesn’t have its airflow restricted by walls, bushes, or other objects. The outdoor unit needs to move air across the condenser coil to reject the heat absorbed in the building. If the condenser is not getting proper airflow, there will be a loss in cooling capacity.

Bad Indoor Fan Motor

The indoor fan moves the air over the evaporator coil. If the fan is dirty or has malfunctioned then little to no air will be coming out of the supply grilles. You can turn the thermostat setting to fan only to see if the fan is blowing at its normal rate. If nothing comes out when set to fan only there is a good chance something is wrong with your fan motor or a capacitor or relay.

Thermostat

Make sure that the stat is on and has power, and that the proper settings have been entered. Check to see that the setting for cooling is lower than the current room temperature. If it’s a new thermostat, then re-read the instructions to ensure proper installation and setup.

Thermostat
Thermostat

The Obvious

Make sure windows are closed and air vents are open. Make sure nothing is blocking the return air opening. 

When done of the above helps improve the cooling, then it’s definitely time to call a professional air conditioning technician who can properly diagnose the problem. Here are a few things they may discover.

Leaking Refrigerant System

If there is a refrigerant leak in the system, the cooling capacity will be diminished. If a leak is suspected the technician will be able to tell by checking the temperature and pressures of the system, much like the doctor listening to your heart.

Refrigerant Leak Detector
Refrigerant Leak Detector

The refrigerant is the medium by which heat is moved from one location to the other, such as absorbing the heat indoors and rejecting it at the outdoor unit. If low on refrigerant the system compressor could burn out.

Compressor Malfunction

This is definitely one of the most expensive problems to occur. The compressor is the heart of the system and is responsible for circulating the refrigerant from the indoor coil to the outdoor coil. If the compressor burns out, it may be time to look at an updated air conditioner with a better energy rating if your system is 10 years old or older.

Capacitor or Relay

Hopefully the compressor is all good and it’s just a capacitor, that small shiny object in the outdoor unit that holds an electrical charge for assisting in the starting of the compressor. Or maybe it’s a relay contactor, those electric devices that allow electricity to certain parts of the unit when requested. A malfunctioning relay or contactor is an inexpensive fix compared to other repairs. 

Capacitor and Contractor - Less Expensive Fixes
Capacitor and Contractor – Less Expensive Fixes

Frozen Indoor Evaporator Coil

The indoor evaporator coil is located above the furnace or in a sheet metal housing the indoor heat pump section. A frozen coil can occur when the refrigerant runs low or airflow to the indoor evaporator coil is restricted, like when a filter is clogged. Can you see any frost on the copper tubing leaving the evaporator coil, or is there excessive water dripping at the indoor coil? 

Undersized Air Conditioner

Hopefully the engineer or installing contractor perform a load calculation to determine the correct size for your space. Rules of thumb should never be used for the proper sizing of air conditioners. If it is determined that the system was undersized look at supplementing the existing system with a split system for a particular area with different usage patterns and re-duct the air from that space to serve the rest of the spaces.

Over-sized air conditioners are also a problem as they frequently cycle on and off, without the proper run time to remove moisture from the air, leaving the space cool but clammy. 

Minimum Maintenance you should provide for your Air Conditioner.

  1. Replace filters seasonally or sooner based on usage.
  2. Inspect and clean if required Condenser and Evaporator Coils seasonally.
  3. Inspect and lubricate fan motors seasonally.
  4. Flush and blowout condensate piping
Why is my Air Conditioner not working

Plumbing Estimating Spreadsheet

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Plumbing Estimating Spreadsheet

This Plumbing Estimating Spreadsheet was created by a 40 year veteran of the Commercial Construction Industry. It contains everything you’ll need to bid a small project to projects worth millions of dollars. Check out this easy to use Plumbing Estimating Spreadsheet and establish accurate estimates.

If you prefer to watch the YouTube Video of this presentation then scroll to the bottom or click on this link Plumbing Estimating Spreadsheet

Win more bids by knowing your cost and having a spreadsheet that includes everything from labor and burden rate tables, plumbing fixture labor and material sheets, plumbing equipment, plumbing material and labor summary sheets to name a few. This estimating spreadsheet will save you time and money bidding projects and increase your accuracy.

All aspects of the cost of furnishing and installing a Plumbing system is contained in one spreadsheet made specifically for the MEP industry. We’ll cover each of the tabs available in the Best Plumbing Estimating Spreadsheet available anywhere. We’ll start with the Plumbing fixtures tab.

Plumbing Fixtures

the spreadsheet has a line item for all of the typical plumbing fixtures you’ll find on a residential or commercial projects, plus many lines to add more. Each line has a fixture value that you can assign so that the spreadsheet automatically calculates the project cost per fixture for a sanity check.

Estimating Plumbing Fixture Material and Labor Cost.
Estimating Plumbing Fixture Material and Labor Cost.

There are three additional columns not shown above that are used for vendor quote comparisons.

Plumbing Crew Size, Labor Rates & Burden

Easily calculate the total cost of labor including labor burdens.

Plumbing Crew Size and Labor Rates
Plumbing Crew Size and Labor Rates

The labor tab includes categories for General Foreman through 5th year apprentice. If you have a non-union company then you can easily change the descriptions to fit your labor designations. Starts with base wage and benefits, plus employer tax obligations and burden. There is also a burden calculator to help you figure the cost to be recovered for burden expenses. Also, included is a separate section for shop labor (not shown above).

Plumbing Equipment

This sheet is where you could put anything not counted as a fixture such as Boilers, Water Heaters, Pumps, Storage Tanks, etc.

Plumbing Material and Labor Summary

This is the sheet that totals all the material and labor where you can do a quick review of the overall trade numbers. Add the total feet of piping, including material cost and labor for each of the piping services, such as Domestic Water, Gas Piping, Waste & Vent and Storm piping.

Plumbing Material and Labor Summary Sheet
Plumbing Material and Labor Summary Sheet

Included is a section to adjust labor and measure the performance using field labor metrics. Also included is a section to calculate detailing time required for any project requiring detailers.

Plumbing Specialties

This tab is for the material and labor cost that are considered specialties because they don’t fit into any other category. They’re not plumbing fixtures or equipment per se, but items that need to have material and labor cost applied to them, such as pressure testing, pipe ID’s, Special Valves or Meters, seismic bracing, etc.

Plumbing Assemblies

This page is a time saver by having all your common fixture and equipment trim already preset, just select the size and quantity. Setup this page with the most common fixtures and equipment that you use repeatedly and for which you can list all the parts and pieces along with the labor. If you’re familiar with assemblies you’ll know this is a big time saver.

Plumbing Assemblies make takeoff's quicker
Plumbing Assemblies make takeoff’s quicker

Rental Sheet

here is where you can put all the typical pieces of equipment that you normally rent and the cost for the rental period. Instead of calling the rental yard for every bid, just keep track of the typical cost of rental equipment.

Plumbing Rentals Sheet
Plumbing Rentals Sheet

General Conditions

on this sheet of the plumbing estimating spreadsheet you’ll put your reoccurring project management fees, job site Office Fees,

Subcontractors

This sheet is where you’ll find your typical plumbing subcontractors like insulation, chlorination, excavation, etc. Just record the quotes from each of the subcontractors, compare then and select the subcontractor cost to carry.

Engineering

If you do you own engineering then you can easily set this up with the typical cost for your in-house engineering teams fees, or if you hire engineering firms and know their rates enter them here. This works well for those companies that do design/build work.

Main Estimating Summary Sheet

This is where all the cost is carried forward and you add your overhead and profit percentages along with any contingency.

Main Estimating Summary Page (Upper Portion)
Main Estimating Summary Page (Upper Portion)

Dashboard of Plumbing Estimating Spreadsheet

The dashboard provides a quick visual overview of the total project along with cost metrics that let you compare one project against another. This allows you to learn what metrics are important to keep track of, and allows you to quickly spot something that doesn’t look correct. Below is a screen shot of the upper portion of the Dashboard.

Plumbing estimating Spreadsheet Dashboard
Plumbing estimating Spreadsheet Dashboard

The following additional sheets will help you manage your estimating process and determine if a project is worth spending the time and money to pursue.

Risk Assessment Sheet

This sheet allows you to assess the risk and rewards of pursuing a proposed estimate based on very real risk. Fill out the form to determine if the project is worth pursuing based on the values you give each category. This sheet can notify the estimator or salesperson if they need to get upper managements approval due to a poor risk rating.

Plumbing Specification Review Sheet

This sheet allows the estimator to record the important sections of the specifications. Using this sheet you can enter those items that are commonly seen in specifications in your region, and as a reminder for the estimator to search for in the current specifications.

Bid Notice Sheet

This allows you to document the important aspects of the project that bidding, such as bid date and time, job walk dates, deadlines for RFI’s, etc.

Click on this link to get this best in class Plumbing Estimating Spreadsheet.

Plumbing Estimating Spreadsheet

How to Calculate Air Changes per Hour

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How to Calculate Air Changes per Hour

How to calculate air changes per hour (ACH). How do you calculate how much air or CFM you need to provide to achieve a certain number of air changes?  We’ll show you how to determine the amount of CFM or air required for a space based on the required air change rate per hour. Often specifications or standards will mandate a minimum air change per hour for a room for ventilation purposes, odor control, pressure relationship between spaces, or to achieve a cleanliness level like in a cleanroom or operating room.

If you prefer to watch the YouTube video of tis presentation, then scroll to the bottom or click on this link. How to Calculate Air Changes per Hour

Air changes per hour is an indication of how many time the air within the space is exhausted, recirculated through the system, or recirculated within the space. 

We’ll cover how to calculate CFM and Air Changes using several different examples, including Hospitals and Cleanrooms. 

Air Change Rate per Hour Formula

The formula for Air Changes per Hour looks like this:

How to calculate air changes per hour
How to calculate air changes per hour. Formula for Air Changes per Hour

Air Changes per Hour = CFM x 60 / the Volume of the room

We can express it another way in order to calculate CFM as

CFM = Air Changes / Hour x Volume of room / (60 Minutes/Hour)

High Rates of ACH for Cleanrooms

Cleanrooms are hidden from our view but they are used throughout the industry for businesses such as Food Manufacturing, Pharmaceuticals, electronics manufacturing of computer chips, and any product requiring a clean environment.

Cleanroom Air Changes per Hour
Cleanroom Air Changes per Hour

Cleanrooms require large amounts of air to be recirculated through the filters to achieve a certain level of cleanliness. Cleanrooms are classified according to ISO levels 1 through 8, with ISO Class 1 being the most stringent or cleanest.

ISO Classification of Cleanrooms - Air Changes per Hour
ISO Classification of Cleanrooms – Air Changes per Hour

An ISO Level 1 cleanroom can require in the range of 500 to 750 ACH and require approximately 80% to 100% of the ceiling to be covered in filtration. ISO Class 8 can require in the range of 5 to 60 ACH and have a ceiling coverage rate of 5 to 15%.

For a cleanroom air change rate example let’s use the following information given to use by the owner.

Space is to be a Class 1 Cleanroom

The measurements of the room equal 12 ft x 20 ft x 9 ft

And the Requirements are 500 Air Changes per Hour minimum

Step 1 is to Determine the Volume of the Room

12 ft x 20 ft x 9 ft = 2,160 ft3

This is the volume that needs to be removed from the space every hour multiplied by the number of air changes required in an hour. The thing to remember is that this is in ft3 an hour, and we need to get the units to minutes, as in cubic feet per minute (CFM).

Step 2 – Determine Required Recirculation CFM

CFM = Air Changes / Hour x Volume / (60 Minutes/Hour)

CFM = 500 ACH x our volume of 2,160 ft3/ divided by 60 to get us to minutes, not hours.

CFM = 18,000

For our second example we’ll use a Hospital

Air Changes for Hospitals

The ACH rate is a common design requirement for various rooms within a hospital. Critical spaces within hospitals require that a certain amount of ventilation air be brought into the room every hour in addition to that, there is another requirement to recirculate the full volume of air a minimum number of times through the system every hour. 

Hospital Air Changes per Hour
Hospital Air Changes per Hour

For example, a Recovery Room may require 2 ACH of ventilation air with a minimum air change rate of 6 for the space. This will require that the volume of outside air for ventilation be two times the volume of the space within an hour and another 4 ACH recirculated through the HVAC system for a total of 6 ACH.

The difference between a hospital room like an operating room and a cleanroom, is that the operating room doesn’t allow the air to be recirculated within the space, as opposed to a cleanroom where the use of fan powered recirculation units are acceptable to achieve the required cleanliness level.

Increased air exchanges reduce odors, increase air quality and cleanliness. There is obviously a cost to increasing the quantity of air changes due to the consumption of fan and or compressor power. Providing the correct amount of air and no more is critical to providing an energy efficient system. When critical spaces are unoccupied, the air change rate should be setback to lower volumes or turned off if allowed.

We used the same volume as the previous example so that you can see what the difference is between the two air change rates.

Hospital Recovery Room ACH

The space Volume is the same as before at 12 ft x 20 ft x 9 ft

The Requirements are 2 ACH of Ventilation with a 6 ACH Minimum

Step 1 again is to Determine the Volume of the Room, which is 2,160 ft3

Step 2 – Determine the Required Ventilation CFM

CFM = 2 ACH x 2,160 ft3/60

CFM = 72 

Step 3 is to Determine the Required Minimum CFM

CFM = 6 ACH x 2,160 ft3/60

CFM = 216

Step 4 is to Determine the Required CFM to be Recirculated through HVAC Equipment

Minimum ACH – Ventilation ACH = Recirculated ACH (This can be stated in CFM)

Recirculated CFM = Minimum CFM 216 – Ventilation CFM 72

Recirculated CFM = 144

You can see that the same size room at the two different air change rates makes a huge difference in the volume of air that must be circulated.  

how to calculate air changes per hour ACH

How Occupancy and Vacancy Sensors Work

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Occupancy Sensors Vacancy Sensors

How occupancy and Vacancy Sensors Work. Where should occupancy sensors be used, and which type is better, hard wired or wireless? What’s the difference between an Occupancy Sensor and a Vacancy Sensor? What does ASHRAE 90.1 require for the controllability of lights in various spaces? Lighting consumes up to 20% of the total energy in commercial buildings. By adding lighting controls considerable energy can be saved based on space usage type and the type of light source, such as incandescent, fluorescent, high intensity discharge or LED.

If you prefer to watch the YouTube video of this presentation, scroll to the bottom or click on this link. How Occupancy and Vacancy Sensors Work

Why use an Occupancy Sensor?

Occupancy sensors are used to detect motion and provide a response by turning on or off lights or HVAC equipment. By monitoring when spaces are being used, a more energy friendly support system of lights and HVAC equipment can be deployed. Various sensing technologies are used, such as Passive Infrared (PIR) and Ultrasonic. There are other technologies such as Time of Flight (ToF), microwave, and camera based technologies that are not covered here.

Hard Wired and Wireless Passive Infrared Occupancy Sensor
Hard Wired and Wireless Passive Infrared Occupancy Sensor

Energy Savings Potential

According to a Commercial Building Energy Consumption Survey, the following savings can be achieved using occupancy sensors for the various space usage types.

Energy is saved by reducing lighting levels or shutting them off when a space is not in use. By adding lighting controls, you can save up to 90% or more of the energy used depending on the space usage type. 

Types of Occupancy Sensors

Communication from the sensor can be hard wired or wireless. Although most sensors are probably hard wired there are some advantages to using wireless sensors in certain applications. Wireless sensors can be battery operated or use photovoltaic (PV) powered sensors and can be easily attached to a wall or ceiling. They’re a possible option where it’s difficult or aesthetically unappealing to run electrical wiring.

The material cost for wireless occupancy sensors is usually more than hard wired, but there will be labor savings from not having to install electrical wiring. Also, the ability to easily move a wireless sensor makes more sense for spaces with frequent layout changes.

Where Should I Use an Occupancy Sensor?

The best candidates for occupancy sensors are spaces that are used intermittently, like bathrooms, meeting rooms, storage areas, classrooms, warehouses, private offices, and breakrooms. Areas to avoid putting sensors in are those that are busy or have a consistent occupancy level during a fixed schedule.

Picture of Locations for Occupancy Sensors
Locations for Occupancy Sensors

Two Lighting Control Strategies

The lighting can either automatically turn on when someone enters the room or require the occupant to manually flip a switch. These are referred to as an Occupancy or Vacancy sensor. The difference is that the vacancy sensor needs to be manually turned on, while the occupancy sensor turns on with motion. When the occupant leaves the room, both strategies will have the lights automatically shut off after a certain amount of time.

How do Occupancy Sensors Work?

The problem for the occupancy sensor is to accurately detect when occupants are present and when they have left the space. This includes the ability to recognize occupants working at their desk or on the other side of a partition. There are various occupancy sensors that accomplish these problems better than others. Here are some of the sensor technologies being used and their advantages and disadvantages. The two most used occupancy sensors are either ultrasonic sensors or passive infrared sensors.

Ultrasonic Sensors

An ultrasonic sensor will emit high-frequency sound waves that bounce around the room and objects, but are not heard by humans. The sensor will pick up any movement by noticing a change in sound wave frequency. This is based on the Doppler effect or Doppler Shift, which is the change in frequency of a wave in relation to an observer who is moving relative to the wave source.

Picture of Ultrasonic Occupancy Sensor
Ultrasonic Occupancy Sensor

Since the Ultrasonic occupancy sensor sends out a continuous signal, the electrical power consumed will be higher than the wireless passive infrared sensor. This will require the ultrasonic to most likely be hard wired to provide the constant energy for operation.

Ultrasonic sensors are good at detecting movement that may occur behind a partition or bookcase which isn’t in the direct line of sight of the sensor. This technology will pickup slight movements of an occupant sitting at their desk reading a book or typing on their computer.

The ultrasonic occupancy sensor has a greater detection range than the Passive Infrared Sensors.

Passive Infrared Sensors (PIR)

An infrared technology-based occupancy sensor is best used in smaller open spaces without obstructions that allows it to easily detect movement. These sensors require that the movement occur within their direct line of sight, as they won’t detect movement behind a partition or bookcase. 

Passive Infrared Occupancy Sensor
Passive Infrared Occupancy Sensor

It’s called passive infrared because it doesn’t send a signal out. The sensor contains a thin film that generates electricity when exposed to heat which occurs when infrared energy is emitted from a warm object passes in front of the floor or wall in line of sight of the sensor. Because the infrared sensor doesn’t constantly send out a signal like the ultrasonic sensor, it doesn’t require the same amount of electrical power. This makes the passive infrared sensor a great option for wireless communication using a battery or PV cells for power. 

The wireless passive infrared sensor will need a source of power for the controller that receives the signal from the sensor and interprets an output signal to increase or decrease lighting levels.

Wallbox sensors are made to fit in a standard electrical switch wallbox and use the voltage available at the box. This makes for an inexpensive and easy retrofit of an existing wall switch. They are limited by their range of vision.

How Long Should Lights Remain on After No Motion is Detected?

The time between no motion being detected and the shutting off or minimizing of the lights is dictated by various standards and codes. The National Electrical Manufactures Association (NEMA) has recommended that 15 minutes after no motion has been detected the interior lights should be shut off, and the 2021 IECC and ASHRAE 90.1-2019 have it at 20 minutes. Exterior lighting and parking garages have different requirements The shorter the time delay the greater the energy savings, but you also want to be sure not to have the lights going on and off too frequently.

Restrike Time

Occupancy sensors work best with light sources that have quick restrike times, that’s the amount of time it takes the light source to reach full value. Anyone who has witnessed the outage of a High Intensity Discharge light knows that it takes up to 15 minutes to reach full value. An outage occurred during a recent night-time football game, which had to be postponed long enough for the HID lights to come up to full brightness. This means that occupancy sensors are not a good choice for HID type lights but work well with quick starting light sources like LED, Incandescent and Fluorescent. 

Where Should Sensors be Installed?

Sensors are best installed on ceilings or walls where interference from doors or air conditioning air flows are not a problem. Wireless sensors can be installed anywhere if motion is within the line of sight of the sensor. This allows wireless sensors to be installed where hard-wired sensors would be difficult to install. 

Range of Sensors (Field of View and Coverage)

Wireless sensors need to be within 15 feet of the floor area or door to work effectively. Check the occupancy sensors manufactures literatures for specifics. If there are multiple obstructions in the space like partitions or bookcases, it may make sense to install hard-wired Ultrasonic type sensors which are better at motion detection in these situations. If wireless sensors are preferred, then more sensors will need to be installed to ensure motion is detected behind any obstructions.

Coverage or field of view can be in a narrow band like 8-degrees for use in corridors or aisles, up to a 360-degree circle, or a 180-degree semi-circle with diminishing capabilities at the extreme angles, and greater distance sensing abilities straight ahead. Sensors are also indicated by their coverage in square feet.

Multiple Levels of Lighting

In areas where there is natural sunlight, there is the option of using bi-level switching. The sensor will detect various levels of natural light and reduce the light fixtures output by half or some other percentage. Existing LED and fluorescent lights may need their ballast or drivers replaced to be compatible with the bi-level capabilities. 

HVAC Controls and Occupancy Sensors

Occupancy sensors can save energy when integrated into the HVAC system control sequences. If the room is unoccupied, a signal can be sent to the HVAC equipment to reset the temperature, reduce the airflow or shut the system off. This would reduce energy consumed to condition an empty space.

How Occupancy and Vacancy Sensors work