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.
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
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
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
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
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)
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
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.
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. 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
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
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
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)
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.
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
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.
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.
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
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 HVAC Split System Air Conditioners Work. Using a Split System Air Conditioner or Heat Pump is common in residential and commercial applications. It’s called a split system because the indoor and outdoor components are separated or split from each other and are connected by refrigerant piping and control wiring. This differs from a self-contained rooftop packaged unit which houses both indoor and outdoor components. We’ll see different designs using split systems.
HVAC Split systems are convenient to use with existing buildings because it’s much easier to route small refrigerant piping to the indoor coil, then to run much larger air ducts using a rooftop packaged unit. As you can see the rooftop unit needs large openings for the supply and return ducts to enter the building. The split system uses smaller copper tubing and requires a small opening in the roof or wall.
Refrigerant Piping Size vs Ductwork Size
Refrigerant carries more heat capacity then air, which allows small refrigerant piping to easily maneuver through building structures and components as opposed to large air ducts. This is what gives split systems their advantage, except when it comes to ASHRAE 62.1, ventilation air requirements, which we’ll discuss later.
Refrigerant Piping Space required versus equivalent Ductwork Space required with equivalent tonnage capacity
The split system is made up of the Outdoor unit, often called the condensing unit, because this is where the refrigerant condenses from a gas back into a liquid, and an indoor unit where the evaporator is located. The indoor unit can be called an Air Handling Unit (AHU), Fan Coil or a Furnace with Coil.
Split systems are available from less than one ton to over 100 tons of refrigeration capacity. Split systems come in two basic configurations, either as cooling only or as a Heat Pump, which we’ll explain later.
Refrigerant Cycle Split System HVAC
Heating in HVAC Split Systems
Heating can be in the form of a gas furnace, electric strip heater, electric heat pump, hot water, or steam. Here we show two ways of getting heat to the occupied space using a split system. First you can use a split system heat pump, which works to cool the space in summer, and heat the space in winter. See our video on How Heat Pumps Work to understand how they work.
Furnace with DX Coil
The other option is to install a furnace with a coil. The furnace will require some form of fuel such as natural gas for heating. Cooling will be accomplished by installing a evaporator coil on top of the furnace, which is connected to an outside condenser.
HVAC Split System with Furnace and DX Coil
The furnace will require combustion air inlet and a means of exhaust combustion gases outdoors. It’s important that the discharge flue remain a minimum of 10 feet away from any air intake, check your local code for the proper distance.
You’ll need to install a condensate drain pipe from the cooling coil drain pan to an approved receptor, like a floor sink or the tailpipe of a sink.
Electrical will need to be installed from a breaker panel to a disconnect switch located near the equipment. The disconnect switch is a safety device that allows any technician working on the equipment to lockout the electrical power feeding the HVAC equipment.
Heating Hot Water Coil
Another option is to use a boiler to provide heating hot water to a coil located inside the air handler. The boiler will need a source of fuel for combustion, in this case natural gas. The heating hot water will need to have a pump to circulate the water to all of the Air handlers in the building.
HVAC Split System using Heating Hot Water Coil for Heating
Here we only show one air handler getting heating hot water, but it could also be dozens more in larger buildings. The heating hot water piping will need to be insulated, most likely with some form of fiberglass pipe insulation to prevent the loss of heat from the pipes. Not shown is makeup water and any other accessories like expansion tanks. This could also be a steam boiler with a steam coil in the air handler to provide heating.
Ventilation Air per ASHRAE 62.1
One of the challenges for split systems is providing the required ventilation air to each of the air handlers. Ventilation air will need to be provided to each space or indoor fan coil or air handler per ASHRAE 62.1. This requires a duct from the outside or from a DOAS unit to the space or fan coil. See our video on “Dedicated Outside Air Systems” for a better understanding.
HVAC Split System with DOAS Unit for Ventilation Air
Dedicated Outside Air System
This Dedicated Outside Air System filters and conditions the outside air before the fan sends it to each of the air handlers. The Dedicated Outside Air System handles the latent load of the ventilation air so that the air handlers won’t need to be upsized for this additional load.
Each air handler will receive the required amount of ventilation air per ASHRAE 62.1 based on the occupancy level, size of the room and space usage type.
Supply Fan with Filtration
Another option is to provide ventilation air using just filtration and a supply fan, but no conditioning of the outside air. This relieves the indoor air handlers fan from needing to pull in outside air. The disadvantage is that the air handler will need to handle the additional heating and cooling load for the ventilation air.
HVAC Split System Air Conditioner using Filtered Ventilation Air
Separately Ducted Outside Air Ducts
The lowest first cost option would be to duct the ventilation air individually from each indoor air handler. This would require additional energy of the air handler fan and coil. This would require a lot of small ducts running through the building from each air handler, unless you required an economizer for your indoor air handler because it meets the threshold of your energy code, then the ducts would be much larger and may not make sense.
Split System HVAC Unit with Individually Ducted Outside Air
As shown before, each air handler has a condensate drain going to the tailpiece of the sink.
Condensing Unit
The condensing unit contains two major components, the compressor, and the condenser coil. The compressor is the heart of the unit and pumps the refrigerant around the piping circuit. The condenser coil provides a means of rejecting the heat to the outdoors using a fan blowing air over a hot coil.
In this picture we can see that this condenser hasn’t been maintained and is covered with dirt. This will reduce the capacity of the unit, so be sure to check your outdoor coil at least once or twice a year to ensure its clean.
Condenser Unit with a Dirty Condenser Coil.
We can see the hot gas discharge piping coming off the top of the compressor and feeding the condenser coil which is responsible for rejecting the heat from the building. But in this poor condition it won’t be working. Here is the filter drier that’s on the hot liquid line leaving the condenser and sending liquid to the expansion valve at the evaporator. Here is the suction piping that has arrived from the indoor evaporator section and is entering the compressor below the discharge piping.
This is the ugly insides. Here is what the condenser may look like from the outside.
HVAC Condenser (Outdoor Unit)
There will also be some controls on the outdoor unit that communicates with the indoor unit and provides various safety components to protect the compressor and the other system parts. The communication from a thermostat or space sensor is typical for a residential unit, while in commercial installation there could be the addition of a BACnet card that allows communicating with a Building Automation System (BMS).
Outdoor units will contain one compressor for smaller sizes and multiple compressors for larger systems.
The condenser can also be air-cooled, water-cooled or evaporatively cooled.
Indoor Unit Air Handler (DX Fan Coil)
The Air Handler contains the indoor fan and evaporator coil. The evaporator coil is where the refrigerant absorbs the heat from the building air that is being blown over the coil. This causes the refrigerant liquid in the evaporator to evaporate while cooling down the building air, see our video on “Refrigerant Cycle 101” to better understand how a refrigeration cycle works. The expansion valve or metering device separates the high side from the low side and modulates the amount of refrigerant that passes through it in relationship to demand.
The indoor unit can be ducted or ductless.
Ductless and Ducted Air Handlers or Fan Coil in a Split System HVAC Unit
Residential systems are relatively simple and smaller, while the commercial versions can be very large and have many other options installed within their housing. Commercial air handlers can be packaged, custom made, or built-up with individual components selected and field erected. See our other video on “Air Handling Units” for a better understanding.
Compressors
The smaller residential units under 10 tons will most likely have 1 compressor, while commercial units 10 tons and over can have two or more compressors. Compressors vary in their ability modulate capacity. Smaller system will use a hermetically sealed compressor with a scroll compressor. Larger systems can use semi-hermetic, reciprocating, and scroll compressors in 1 or more configurations depending on size.
Most compressors use oil for lubrication and that oil travels around the refrigerant circuit continuously during operation. It’s important that the oil returns to the compressor at the same rate that it leaves, as the compressor needs to remain lubricated at all times.
Heat Pumps
In addition to the cooling only split systems, there are Heat Pumps which reverse the refrigerant cycle to provide heating also. There is a move in some states and countries to go all electric, such as in California. Heat Pump are all electric so there is no burning of a carbon-based fuel. See our other video on “How Heat Pumps Work” for a better understanding.
One of the differences between a Heat Pump and other cooling only units is that of the metering device. The metering device separates the high-side from the low-side and controls the amount of refrigerant passing through it. The Heat Pump uses a special “Reversing Valve or 4-Way Valve” that allows refrigerant to change direction based on whether in heating or cooling mode. The indoor coil is used as an evaporator to provide cooling during summer, and as a condenser to provide heating during winter. Therefore, you shouldn’t call the outdoor unit a condenser when dealing with a Heat Pump, as it acts as both a Condenser and Evaporator depending on the mode of operation (Heating or Cooling). With a cooling only Air Conditioner, the outdoor unit is always the condenser.
Split System Sizing and Mixing and Matching
Splits systems are often chosen where the outdoor and indoor unit tonnage match, but that is not always the case. Split systems can have the outdoor unit slightly larger or smaller than the indoor unit. By upsizing the outdoor unit, this will allow more latent heat for the indoor unit. The tonnage of the indoor unit can be larger than the outdoor unit to increase the sensible heat ratio and airflow (CFM). Providing an indoor unit that is one size larger or smaller than the condenser maybe safe, but check with the AC Manufacture when mixing outdoor units and indoor unit capacities. This is not allowed with most Heat Pumps.
Residential systems commonly use split systems of 5-Tons and under or multiples of these sizes for larger homes. You might find a 3-Ton unit serving the first floor and another 3-ton unit serving the 2nd floor in a two-story home.
Refrigerant Piping and Number of Circuits
For small split systems where the indoor and outdoor units are relatively close and the pipe routing simple, the use of line sets maybe used. Line sets are available in a coil of ACR copper and are pre-charged with refrigerant, in lengths of 15, 25, 35, 50 or 100 feet. This saves on labor by avoiding field brazing of joints for fittings and couplings. Piping distances are often restricted by equipment manufactures so be sure to check the literature for these requirements if your distances exceed 100 feet or more.
Dual Refrigerant Circuits in a Split System Air Conditioner
Most small split system have only one circuit, but as the HAVC unit gets larger there are dual circuit units available. Dual circuits will require twice as much piping as a single circuit HVAC unit. There will be two suction lines and two liquid lines running from the indoor unit to the outdoor unit. With dual circuits the ability to control capacity is increased in addition to having a backup or redundant circuit incase a compressor burns out. Each circuit has its own compressor.
The DX coil can also be setup in either a single or dual circuit arrangement. The refrigerant can pass through the coil using one path or two. If you’re using a dual circuit condenser than you’ll have a dual circuit indoor coil. Its possible to have a single circuit condenser and a dual circuit DX coil.
Refrigerant Piping Insulation
This is where most installations that we review are lacking in code compliance and application. The proper application of insulation is important in maintaining a well-functioning HVAC split system. If insulation is poorly applied or if the wrong insulation is used, then there will be a LOSS in capacity of the system. This means that the number of tons of air conditioning that was installed will be less than that. See our video on “Refrigerant Insulation” for the proper installation and type of insulation to be used when installing refrigerant piping.
Condensate Drain
Cooling coils remove moisture from the incoming air, and that moisture condenses on the evaporator coil. The water trickles down the coil and is captured in a drain pan that sits under the cooling coil. The drain pan needs to have some way to empty this accumulation of condensate water. Piping is provided from the drain pan to approved receptor, which could be a floor sink or the tailpiece of a regular sink.
The drain piping needs to pitch in order to avoid overflowing the drain pan. If the piping can’t be pitched per the slope required by the local code, then a condensate pump will need to be added. The condensate pump will raise the level of the water in the piping so that it can meet the required slope or pump directly to the receptor. See our Video on “Condensate Drain Piping”.
Controls
The controls on most split systems are very simple, especially residential split systems. A thermostat calls for heating or cooling and the system initiates startup. For systems with more than one circuit, if the first circuit can’t satisfy the demand then the second circuits solenoid valve would open adding additional cooling capacity to the system. The circuit board for controls is usually mounted in the outdoor unit with control wiring connect the indoor unit to the outdoor unit.
Adding Building Management System (BMS) oversight or connectivity is an option usually implemented on commercial properties. This allows the building engineer or management company complete oversight using graphical interfaces to see what is happening with each system connected to the BMS.
In addition to controlling the overall unit, the system has safety controls that operate to protect the equipment. This could include high and low pressure switches to prevent excessive and minimum pressure levels respectively. There are safety devices to protect the equipment from too much electricity or excessive temperatures.
Advantages and Disadvantages of an HVAC Split System Air Conditioner
One of the biggest benefits is that they come as a packaged unit, already engineered by the manufactured with matching outdoor and indoor units.
Split systems are less invasive for remodeling projects, allowing smaller refrigerant piping to be run to a space instead of larger air ducts. This is beneficial when the indoor space is several floors below the roof, as no vertical duct shafts are required as with a Rooftop unit.
Split system outdoor units weight less than a one piece packaged unit.
Split systems require smaller openings in the structure for refrigerant piping to pass from the outdoor unit to the indoor unit, as opposed to air ducts.
Split System outdoor units are smaller than Rooftop Units, so they are easier to hide. This can be important when the building has large skylights or line of sight code compliance issues.
Split systems usually cost more on new construction projects because they require several points of connection for the electrical and refrigerant piping to connect the outdoor and indoor sections together.
Split systems will require some method of getting the required ventilation air to each space or indoor fan coil per ASHRAE 61.2
