Blog - Page 24 of 50 - MEP Academy

Heat Recovery Ventilator

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December 27, 2022

Learn how a Heat Recovery Ventilator works. The purpose of the Heat Recovery Ventilator is to transfer sensible heat between the incoming and exhaust air streams, and to increase indoor air quality. Instead of wasting the heat, it’s recovered from the exhaust stream in cold climates and in warmer climates the incoming hot air is cooled down by giving up some of its heat by the cooler exhaust leaving the building.

If you prefer to watch the video of this presentation scroll to the bottom or click this link ” Heat Recovery Ventilator and How They Work“

Ventilation air is required for human health and indoor air quality. The conditioning of this outdoor air takes lots of energy. By using a heat recovery ventilator, the load on the air conditioner can be reduced, thereby creating a more efficient system.

Checkout these Heat Recovery Ventilators here

We’ll explain how they’re built, how they work, how to size them, and the three different ways that they can be used with or without air conditioning.

How a Heat Recovery Ventilator is Constructed

The heat recovery ventilator is made of a painted galvanized steel housing. There is a supply and exhaust fan capable of multiple speeds. There should be washable and/or disposable filters at the intake to both fans to keep the fans and heat exchanger clean. Some commercial HRV’s allow for final filters, which is a second set of filters of higher quality.

Then there is the air-to-air heat exchanger which is made of polypropylene or aluminum. There will be a 120-volt power cord that plugs into any nearby outlet or hard wired to a circuit breaker in a nearby electrical panel. A low voltage control wire will be routed from the controller to a connection on the ventilator.

A drain pan and drainpipe will be needed to carry away any water that accumulates during heat transfer or the defrost cycle. There will need to be two holes cut in the exterior wall to allow for the ventilation intake and exhaust grilles. Ductwork will be routed from the grilles to the heat recovery ventilator. The ductwork can be pre-insulated flexible duct or rigid round with insulation.

HRV manufacturers position their fans and filters differently. Some will have the filter before the fan and some after. Some will configure the fans in a blow through arrangement while others use the draw through method.

How a Heat Recovery Ventilator Works

First its best to remember that heat moves from a warmer object to a cooler one as defined by the second law of thermodynamics. Heat will always seek to equalize itself with any cooler objects it meets. Therefore, you wear a jacket in winter, to retain the heat in your body and avoid it from equalizing with the cold outdoor air.

Now we’ll explain three common methods of using a Heat Recovery Ventilator. One method is used without an air conditioner or furnace, the next one with an integrated A/C system, and the final one integrated with all connections on the return duct feeding an air conditioner.

Checkout these Heat Recovery Ventilators here

Heat Recovery Ventilator (Non-Integrated System)

Ventilation air Ductwork will be routed from the outdoors through the heat recovery ventilator to various rooms, like bedrooms, living rooms and family rooms. It’s recommended to design the airflow so that the fresh air is routed from clean spaces to rooms where the air is to be exhausted because of odors. This would have the fresh air travel into the bedroom and then be exhausted through the bathroom, kitchen or laundry room where smells are generated.

Heat Recovery Ventilator without Air Conditioning

This will provide a good path for fresh air to enter spaces where occupants are sleeping and living, while exhausting areas that generate smells or have stale air. This moves fresh air from clean areas through dirty areas. Now let’s add an air conditioning unit to the space.

Heat Recovery Ventilator integrated with Air Conditioning System

This will require an outdoor unit and an indoor air handler. See our video on “How Split System Air Conditioners or How Heat Pumps Work” for an explanation of these systems. The indoor and outdoor units are connected with refrigerant piping.

Heat Recovery Ventilator with Heat Pump Unit

The heat recovery ventilator works the same way but is connected directly to the return air duct of the heat pump unit. The fresh air duct will need a manual volume damper to balance the air volume. The fresh air will be distributed through the existing air conditioning or furnace supply air ductwork. This requires that the air conditioner is running any time the heat recovery unit is running. There is an interlock between the two systems to ensure that one is not running without the other.

A backdraft damper should be provided in the return air duct upstream of the fresh air connection. This will avoid the heat recovery ventilator from pushing air backwards through the return air ductwork if the air conditioner was off or failed. Also, the distance from the return air connection to the air conditioner to where the fresh air tap into the return air is dictated by code, check your local code for distance requirements. Some manufacturers require at least 10 feet (3 m)

If the building has more than one air conditioner, there will need to be a separate Heat Recovery Ventilator for each.

Checkout these Heat Recovery Ventilators here

Heat Recovery Ventilator integrated with Return Duct of A/C System

The heat recovery ventilator works the same way but once again is connected differently. Both the fresh air intake and exhaust are connected to the return air ductwork. Instead of taking air directly from the bathroom, kitchen or laundry areas, this system arrangement just exchanges enough return air with the required amount of fresh air.

Heat Recovery Ventilator with Return Air Duct

The bathroom and laundry rooms can have their own exhaust fan while the kitchen will have a range hood to exhaust air when cooking on the stove.

How to Size a Heat Recovery Ventilator

For small residential properties various equipment manufacturers provide convenient charts based on a quantity of cubic feet per minute (CFM) or Liters per Second (L/s) for each room in the home. Bedrooms receive the greatest amount of CFM (L/s), followed by all other rooms. One manufacture recommends 20 CFM (10 L/s) for Master Bedrooms and 10 CFM (5 L/s) for each of the other bedrooms and spaces within the home.

Heat Recovery Ventilator Sizing Chart Based on CFM or Liters/second

Another sizing method uses Air Changes per Hour (ACH). See our video on Air Changes per Hour for a better explanation. One manufacturer recommends 0.35 ACH. The formula would look like this: Total Ft3 of building x 0.35 ACH / 60 Minutes/Hour.

Example: A 30’ x 60’ home

1,800 Ft2 x 8’ Ceilings = 14,400 Ft3

14,400 Ft3 x 0.35 ACH = 5,040 Ft3

5,040 Ft3 / 60 minutes = 84 CFM (40 L/s)

Winter Mode

Cold fresh air is brought into the ventilator through a filter by a blower fan. The blower sends the cold air into the heat exchanger where it absorbs heat from meeting the material of the heat exchanger. The heat exchanger is warmed up by the exhaust air leaving the building. The exhaust air is brought in from the spaces within the building. The exhaust is filtered before the blower and then sent across the heat exchanger, before being thrown outdoors.

A heat recovery ventilator brings in ventilation air through one end and exhaust air through the other end. They cross paths internally within the ventilators heat exchanger, but the air streams never physically mix, so there is no contamination of the fresh air by the stale exhaust air. Instead, they transfer heat between heat exchanger surfaces that keep the two air streams separated.

If frost accumulates then a defrost cycle could be implemented whereby the supply fan shuts off, while the exhaust fan speed increases. This allows the warm exhaust time to defrost the system when no supply air is brought in. The defrost cycle is turned on by measuring the temperature of incoming ventilation air. If the air is too cold the defrost cycle commences for a fixed time.

Summer Mode

The process is the same as in winter except that warm air is now brought in with the ventilation air. The blower sends the warm fresh air into the heat exchanger where it rejects heat as it crosses paths with the cooler exhaust air. The heat exchanger is warmed up by the ventilation air entering the building. The exhaust air is from the bathroom, kitchen and laundry as we showed before. The cooler exhaust air is filtered before the blower sends it across the heat exchanger where it picks up heat, before being exhausted outdoors.

Heat Recovery Ventilator versus an Energy Recovery Ventilator

First, we need to explain that there is a difference between a Heat Recovery Ventilator (HRV) and the Energy Recovery Ventilator (ERV). An Energy recovery ventilator removes both sensible and latent heat (humidity), while a heat recovery ventilator removes only sensible heat. Remember that sensible heat involves raising or lowering the dry bulb temperature of the air and doesn’t include the energy required for water vapor to change state. Latent heat is associated with water vapor and humidity.

Heat Recovery ventilators are cost effective at reclaiming heat during winter and are used in colder climates, while energy recovery ventilators are used in warmer humid climates to help control humidity.

Heat Recovery Ventilator Control

There are various methods for activating the heat recovery ventilator.

Thermostats can turn the unit off and on based on temperature or fan only status. Remember if the ventilator isn’t running, there won’t be any fresh air coming into the building by this method.

If used with Carbon Monoxide Detectors, some manufactures offer an interface connection that would allow the fan to go into high-speed mode. This would assist with CO dilution and exhaust.

These units can also use a humidistat to control the speed of the fan. When humidity levels get too high within the space the humidistat can call for the fan to go into high-speed mode. Humidistats can be in bathrooms, laundry rooms or kitchens where moisture is generated. But remember, this is a heat recovery unit, it does not remove latent heat or moisture.

A remote timer can be used to allow occupants to turn the heat recovery ventilator on for the duration that they plan to occupy the space. There are also programmable fan timers that can be set to allow the system to come on and off throughout the day based on a schedule.

A simple switch could be used to allow occupants to turn the unit on and off as they wish, or the switch can allow for high-speed fan operation.

The recovery ventilator could also be connected to a building management system in a commercial application.

Heat Recovery Ventilator Maintenance

Remember to disconnect the power before performing any maintenance or hire a professional to avoid unintended accidents.
As with any air moving equipment, filters will need to be cleaned or replaced every quarter or based on usage.
Clean the fans of any dust or grease that may have attached itself to the fan blades and fan housing.
Check the drain opening and connected piping to ensure that the pathway is clear for condensate to flow unobstructed.
Inspect the ventilation intake grille to ensure that the opening isn’t clog with debris like leaves and trash.
Have the air ducts inspected and cleaned, if need be, or replaced if in poor conditioned. A dirty or leaking air duct will reduce the performance of the heat recovery ventilator.
Clean the heat exchanger of any dust that may have accumulated. Some units allow for the easy removal of the heat exchanger and allow cleaning with a warm water/detergent solution. Check the manufacturers literature for maintenance and cleaning requirements.
Make sure to maintain all clearance requirements for the removal of the core and fans. The manufacturers literature will indicate the required clearances.
Do not exhaust clothes dryers, flammable fumes, dusty environments, or appliances.

1 CFM = 0.47189 L/s

1 L/s = 3.6 m3/Hr.

The heat recovery ventilator is designed to recover or reject heat in homes, hotels, offices, meeting halls and just about anywhere except where the air contains coarse dust, soot, flammable, or explosive mixtures, or any dangerous or harmful substances.

Heat Recovery Ventilator and How They Work

Digital Planner for Construction Estimators

MEP Academy Instructor

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December 22, 2022

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Digital Planner for Construction Estimators. This is the only digital planner especially made for construction estimators that allows for tracking of all the important task of the job.

The digital planner is automatically linked to all the pages, just click any link and it will take you to that page. This digital planner is available for the GoodNotes and Notability Apps.

If you prefer to watch the video of this presentation then scroll to the bottom or click on this link Digital Planner for Construction Estimators

Bid Schedule

Let’s start with the Bid Schedule. Here is where you will list all the projects that you’re currently bid including the bid due date and time, any job walk and RFI deadline dates and who it bids to. The first item which is the Estimate number is used throughout the planner to track all the documents related to that particular project.

Bid Log

The bid log is a history of all your bids for the current year. Here is where you can quickly go to see the date of any project you bid, the amount of the bid, the corresponding material take off pages which we’ll show shortly.

Keep Track of all your estimates in one neat file according to the year it was bid

The delivery method whether plans and specs or Design/Build or any other method, and whether you were successful. Keeping track of your wins and losses for the year will help you at the end of the year to do a wins/loss percentage and to see what type of jobs you were most successful at.

Project Details

Next we’ll hop over to the “Project Details” page where you can quickly see the address of the project and the key players, like owner, Architect, Engineer. Who the competition is. If bid bonds, Performance and Payment bonds are required.

Delivery method, and if Liquidated Damages apply. If there is a owner budgeted amount. If there are any labor requirements, such as prevailing wages, any disadvantaged enterprise participation requirements, bid meetings, and a place to indicate a brief scope of work.

Job Walks

This form keeps track of all your job walks and a list of those in attendance and it records any important details that need to be noted.

RFI Log

There is an RFI log to track when RFI’s are due and if and when you submitted any with a brief description of the scope.

Quantity Takeoffs

You can do material takeoffs if you like and it will remain in your digital planner for ever. Document the drawing and detail number along with a description of the item required. Back at the office input the required material and labor cost for a quick estimate.

Material Takeoffs are easily documented in the digital planner.

Project Meetings

Keep track of all your project meetings for the year in one neat digital planner. This is a record of when and where meetings are held, and who was in attendance, along with notes of what was discussed and the important items that need your attention.

Specification Review

Record all the important sections of the specifications to ensure that you don’t forget to cover the cost of high impact specification sections.

Goals

List your personal and business goals. Remember if you write it down you’re more likely to accomplish your goals. So start tracking your goals.

Misc.

This is for anything you want it to be.

Note Paper

Somewhere to take additional notes for later review. Items that may not fit in any other category.

Things to Do

List the important things that you need to get done every day, starting with this most important to your success in life and business.

Graph Paper

Somewhere for you to make sketches of project conditions or when discussing construction projects with the owner, contractor or sub.

Monthly Calendar

The digital calendar includes all the months for the year.

Yearly Overview

Included is the complete yearly calendar for quick reference.

This digital planner has everything you need to keep accurate records of your complete year of estimating, all in one easy file.

Any of the pages can quickly be duplicated, allowing for an endless amount of projects and estimates for the year.

Start keeping track of all your estimates by requiring a digital planner of all your estimators.

The planner is available with the following link. Digital Construction Planner

Digital Planner for Construction Estimators

How do Geothermal Heat Pumps work

MEP Academy Instructor

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December 19, 2022

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How do Geothermal Heat Pumps work? We’ll learn the different types of Geothermal Heat Pump Systems, along with information on where to find incentives and rebates, the efficiency compared to a regular heat pump and the cost you might expect to pay to have one installed.

If you prefer to watch the video version of this presentation than scroll to the bottom or click the link here “How do Geothermal Heat Pumps work?“

Ground Source Heat Pumps - Ground Temperatures and Loop Depth — Ground Source Heat Pumps – Ground Temperatures and Loop Depth

The use of geothermal heat pump systems takes advantage of the earths relatively constant temperature beneath the surface based on location and height. The earth maintains a ground temperature range from 45°F (7°C) to 75°F (21°C). taking advantage of this natural heat source is what gives the Geothermal Heat Pump greater efficiencies than a standard heat pump. This source of heat is also naturally renewable making it a great energy source.

The Geothermal Heat Pump System comes with various options on how to tap into this natural reservoir of heat. We will discuss open and closed loop systems, and horizontal versus vertical system, and when to use them.

Checkout these Geothermal Heat Pump here

The cost of a geothermal heat pump system is more than that of a typical heat pump system, but this cost is saved by possible incentives and rebates in addition to the yearly energy savings which we’ll cover shortly.

Geothermal Heat Pump System in Cooling Mode

Geothermal Heat Pump in Cooling mode

In cooling mode, warm air from within the building is brought into the ground source heat pump. The heat pumps indoor coil will absorb the warm air into the cooler liquid refrigerant circulating through the coil. Absorbing the heat will cause the refrigerant to boil and turn into a gas. The refrigerant will circulate through the system and be absorbed by the cooler water circulating through the system from the underground.

The heat is then absorbed by the water and circulated underground where the heat is rejected to the cooler ground. Remember the 2^nd law of thermodynamics states that heat moves from a warmer to a cooler item. The water and refrigerant never come in contact with each other. For a complete understanding of the refrigerant cycle see our other video.

Geothermal Heat Pump System in Heating mode

Geothermal Heat Pump in Heating mode

In heating mode the opposite occurs. We will always follow the heat as stated by the second law of thermodynamics. The heat in this case is provided by the ground. The cool water is circulated to the ground where it absorbs heat from the ground.

This warm water then circulates into the ground source heat pump where it is absorbed into the refrigerant causing the liquid refrigerant to boil and turn into a vapor. The hot refrigerant is then circulated to the indoor coil where it comes in contact with the cooler return air from the space. The cool return air absorbs the heat from the hot refrigerant and heats the leaving supply air.

Checkout these Geothermal Heat Pump here

Types of Geothermal Heat Pump Systems

In order to tap into the earths free source of energy we’ll need to run plastic tubing beneath the surface. This tubing acts as a heat exchanger between the fluid in the tubes and the ground. The tubing is configured in various patterns and depths based on available land area and the composition of the soil below ground.

If there is enough ground area and the soil is good for heat transfer than a horizontal system can be installed. If there isn’t enough ground area or the soil isn’t good for heat transfer, then vertical tubing is another option. These systems circulate water with antifreeze or there is the option to use a refrigerant based system. Another option if you have a body of water nearby is to use an open or closed loop system into the body of water. We’ll cover each of these now.

Horizontal loop GSHP

Given enough area for the tubing to achieve the heat transfer required to support the cooling and heating load of the building or home, using the horizontal loop is more feasible than drilling vertically. Horizontal loops are buried from 3 to 5 feet (0.9 to 1.5m) deep and are economically feasible as long as excavation can be done without difficulty due to soil composition.

Geothermal Heat Pump Horizontal Trench with Looped Tubing

The length of the loop is determined by the amount of heat transferred required or the tonnage of the heat pump. In order to determine the length of tubing required, a heating and cooling load calculation is performed on the building. Tube length can run between 500 to 600 feet (152 to 182m) per ton of heat pump capacity. This means that a 4-ton system would require 2,000 to 2,400 feet (610 to 732m) of tubing. Allowing for spacing to achieve efficient heat transfer, an approximate area from 1/4 to 3/4 acre could be required for a typical sized home.

Vertical Loop GSHP

Using vertical loops requires less land area as the tubing is sent hundreds of feet below the surface. For commercial buildings this could include bore holes 100 to 500 feet (30 to 152m) deep, spaced 20 feet (6m) apart to allow for proper heat transfer. These holes can be up to 4” to 6” (10 to 15cm) in diameter and contain plastic tubing that traverses to the bottom where it makes a U-turn and comes back out of the hole where it connects to a horizontal manifold. Residential systems would require fewer bores and would most likely be 300 feet (91m) deep or less. Vertical loops can be used when there isn’t enough land area and when greater efficiency maybe required.

The Slinky Geothermal Loop Installation

This geothermal System uses coiled tubing which allows for the use of less area by increasing the heat transfer ability per area used. This occurs because the tubing is coiled in the trench requiring less land area, but more tubing per linear feet. The coils are laid in a horizontal trench 3 to 8 feet (1 to 2.4M) deep. A combination of water and antifreeze circulate through the tubing and the heat pumps heat exchanger.

DX Refrigerant Based Geothermal Ground Loop

Another energy efficient option is the DX ground loop system that uses refrigerant circulating around a buried copper coil. Instead of water, refrigerant is the heat transfer medium, avoiding the additional step of transferring the heat to the refrigerant in a water based system. This helps with the increased efficiency and greater heating capacities. This also eliminates the need for a water pump, as this is a waterless system.

Another difference is that this loop is in a wide vertical hole, something like 3 feet (1m) in diameter and 70 feet (21m) deep. This eliminates the need for large areas of land. The soil will need to be tested to make sure it’s not corrosive to the copper, and if found to be corrosive then a ground loop protection method will be installed.

Checkout these Geothermal Heat Pump here

Ponds, Lakes or Water Based Sources

Having a body of water near the property allows for the option of using water as the heat sink, where heat is transferred to and from the tubing either in an open or closed loop arrangement.

Ground Source Heat Pump - Closed and Open Loop Systems — Ground Source Heat Pump – Closed and Open Loop Systems

Closed loop Systems.

The tubing can be installed at the bottom of a pond on the property if the pond is large enough, maybe 1/2 an acre or larger depending on its depth. If close enough to a lake this option is also available pending local authority approval. A pump circulates the water and antifreeze solution through tubing within the body of water where it rejects or absorbs heat from the geothermal heat pump.

The use of lakes, wells, ponds or waterways for a heat sink.

Open Loop System

The difference between the closed and open loop systems is that the open system uses the pond, well or lake water to be circulated through the tubing and up to the heat pump. This raises additional concerns for environmentalist and code authorities about water depletion and ground water contamination.

The use of well water is an option if a body of water exist under your property and the use of a horizontal ground loop doesn’t work for lack of area or feasibility. Open loop systems require more maintenance than a closed loop, due to the minerals and other impurities that maybe in the water.

Are open loop Systems Legal?

There are laws governing the use of bodies of water for the use of any open system that will take water from the source and use it in some process before returning it back again. The legitimate concern is what happens to the quality of the water in the process. Another concern is for the wild life or living organism in the water that maybe effected by the warmer discharge temperatures.

You’ll need to check with the jurisdictional authority when contemplating the use of any body of water. An alternative would be a closed loop system which should be less stringent.

Is a Geothermal Heat Pump System worth the Cost?

Energy savings from the installation of a geothermal heat pump system could take anywhere from 5 to 10 years to payback the additional investment cost above a conventional system according to the department of energy.

The DOE states that an average geothermal heat pump system costs about $2,500 per ton of capacity. If a home requires a 3-ton unit, then it would cost about $7,500 (plus installation and drilling costs). A comparable Air Source Heat Pump system with air conditioning would cost about $4,000, but the energy costs could easily equate to the extra cost of installing a geothermal heat pump.

Geothermal heat pump systems have an average 20+ year life expectancy for the heat pump itself and 25 to 50 years for the underground infrastructure.

Geothermal Heat Pump System Frequently Asked Questions (FAQ)

1) How Long Do Geothermal Loops Last?

The geothermal loop is buried underground so it’s protected well and should last anywhere from 50 to 100 years. The underground piping often has a warranty period of 25 to 50 years, check with the manufacture about their warranty period.

2) How long does it take for a Geothermal System to Pay For Itself?

Based on the type and size of the project the payback period varies but expect 4 years or more. Ask your contractor for a payback analysis.

3) Do Geothermal Systems use a lot of Energy?

No. Geothermal systems are used for the purpose of saving energy and providing a more sustainable solution. The heat pump uses electricity but more efficiently.

4) Do Geothermal System Require A lot of Maintenance?

No. Geothermal systems require less maintenance than other types of heat pumps.

5) How Deep Should Geothermal Horizontal Loops be?

Anywhere from 3 to 8 feet (1 to 2.4m) deep is a common depth for a horizontal geothermal heat pump system. The tubing can be placed side by side in a couple feet wide trench, or spaced several feet apart at different depths in a more shallow trench.

6) What is better, a Closed or open loop Geothermal System?

A open loop system will be more efficient and less costly, but will be more regulated due to the system discharging into the water way.

7) Can I Install my Own Geothermal System?

The installation is best done by an experienced contractor and is not something a home owner should attempt on their own.

8) Do you need supplemental Heat when using a Geothermal Heat Pump?

A properly sized Geothermal heat Pump should be sufficient to handle the calculated heating and cooling load of a space. This is why it’s important that a load calculation be done to ensure that the system is sized correctly. If need be, additional electric heat can come on after its maxed its capacity

9) Is a Geothermal System worth the investment cost?

One of the greatest benefits of a geothermal system is that they use 25 % to 50% less electricity than your typical heating and cooling system. And efficiencies can be increased by adding a desuperheater that heats the domestic water. If you consider the environment then the investment value is increased as less carbon is injected into the environment.

10) What material is used for geothermal heat pump underground tubing?

The three most commonly used materials for water based systems include PEX (polyethylene), HDPE (high-density polyethylene) and PE-RT (polyethylene (PE) resin).

11) Can my Geothermal Heat Pump be powered by a Solar System?

A PV Solar system can provide the power needed to run a geothermal heat pump. Have your contractor do a comparative analysis between the capacity of the solar system and the required power of the heat pump system.

12) How much does a Geothermal System Cost?

Cost vary by location and type of system installed. Residential systems can range from $25,000 on the low end for a small system to over $60,000 for larger systems. For commercial properties the range is much greater because the system sizes encountered are much larger than residential systems.

13) What size tubing is used for Geothermal Heat Pump Systems?

The loops are typically using 3/4” to 1” (1.9 to 2.54cm) tubing, while the main headers will be larger in the range of 1-1/2” (3.8cm) for a 3-ton system.

14) Are there any Tax Rebates or Incentives for Geothermal Heat Pump Systems?

In 2022 tax credits were extended through 2034 for ENERGY STAR rated geothermal systems. Check local utility companies for incentives and geothermal Heat Pump manufactures for rebates.

Geothermal Heat Pump Process

One of the first things when considering the installation of a geothermal heat Pump system is to engage an experienced contractor. The contractor should develop a plan for the execution of the system starting with the options on the type of Geothermal System appropriate for your site. This should include a site visit from the contractor and a review of the home or space. A heating and cooling load will need to be done on the home to determine the correct size of the system.

Included in the contractors review should be an analysis of the energy savings from the various heat pump systems, including any possible rebates, incentives or tax credits.

How do Geothermal Heat Pumps Work

How do Evaporative Coolers Work

MEP Academy Instructor

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December 13, 2022

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How do Evaporative Coolers Work? Areas with low-humidity levels can benefit from evaporating water into the air supplied for space cooling, whether residential or commercial. There are two basic types of evaporative coolers, indirect and direct evaporative coolers. We’ll be covering direct evaporative coolers, often called swamp coolers, which means that the water used for cooling comes in direct contact with the air stream.

We’ll show you how they work and how they are installed. We’ll also learn how to size an evaporative cooler based on climate zones, along with air flow strategies and how they’re ducted.

If you prefer to watch the Video of this presentation, then scroll to the bottom or click on the following link “How do Evaporative Coolers Work“.

Evaporative cooling involves passing dry outdoor air over water saturated pads which causes the water to evaporate and cool the air delivered to the space.

Swamp Cooler - Direct Evaporative Cooler — Swamp Cooler – Direct Evaporative Cooler

Construction of an Evaporative Cooler

The evaporative cooler is housed in a sheet metal box. Inside the box there is a fan that blows air into the space, and a water reservoir where a recirculating water pump will sit. Then there is tubing from the pump to spray heads above media pads on the air intake sides of the cooler. There is a float valve and float to maintain water in the reservoir, while an overflow drain is provided for excess water drainage.

There are several options on where to install the evaporative cooler. It can be installed on the roof, a wall or on the ground.

Checkout these Evaporative Coolers here

Evaporative Cooler or Swamp Cooler Construction

Roof Mounted Evaporative Cooler

We’ll explain a roof mounted system as it has more steps. After the system has been sized and selected, a hole would be cut in the pitched roof between roof supports for the supply air duct, making sure to seal tightly around the perimeter of the penetration with flashing to avoid leaks. The best location is on the backside of the home to avoid visibility from the front.

Next, you would use a crane or other method to safety hoist the evaporative cooler onto the roof positioned over the duct opening so that it lines up with the evaporative coolers bottom opening. Install support legs to add stability.

Evaporative Cooler Electrical

You will need to install a 120-volt electrical outlet near the unit and run wire inside to a wall switch or a controller. Check your local code as you may also forgo the electrical outlet and just run the electrical conduit and wire directly to the switch from the cooler. The controller will allow for low and high speeds, and for a fan only option. There may also be a pump only option that allows you to give time for the pads to absorb the water before sending hot air over them. Again, you’ll need to have a roof jack where the electrical conduit penetrates the roof. This will ensure that you can make a proper seal to avoid roof leaks.

Evaporative Cooler Water Tubing

A small residential system could use a 1/4” water tube. The tubing will need to be connected to an existing water pipe to provide the cooler with a continuous supply of water. The tubing can be installed in copper, PEX or plastic tubing, check your local code to make sure of the approved material types. It’s best to have one continuous length of tubing in the attic or in concealed spaces to avoid additional points where leaks could occur.

A shutoff valve should be provided at the point of connection to the main water supply to isolate the tubing if there is a leak, and at the evaporative cooler for quick access. In areas that experience freezing winters, it’s a good idea to provide a tee connection near the main water source with a drain valve to drain the tubing to avoid freezing, which could cause damage to the tubing.

Checkout these Evaporative Coolers here

The tubing connects near the evaporative coolers float valve. This tubing will also need a roof jack to prevent roof leaks. There will also need to be a connection for the overflow drain connection as you don’t want unsightly water stains running down your roof.

Evaporative Cooler Ductwork

There are several options when installing the supply air duct. There is the option to have one large opening in a central location like the hallway, hopefully the evaporative cooler can be located directly above and make a simple straight duct drop.

You could also duct the supply air to each room.

Direct Evaporative Cooler ducted to multiple Rooms — Direct evaporative Cooler ducted to multiple Rooms

Frame out around the ceiling opening and install a supply grille. You should never use the existing air conditioning ducts as they aren’t sized for the air volume of an evaporative cooler.

Selecting an Evaporative Cooler

Evaporative coolers are rated by the volume of air that they can provide in cubic feet per minute (CFM). Manufactures recommend that a certain number of air changes be provided depending on the geographical location of the space. For an explanation on how to calculate Air Changes per Hour, see our video on “How to Calculate Air Changes per Hour”. The warmer the climate the greater the number of air changes that will be required.

Air changes could range from 20 to over 40 air changes per hour. For a 1,500 Ft2 home with 8-foot ceilings this would roughly be about 4,000 CFM at 20 Air Changes per hour, or 8,000 cfm at 40 Air changes per hour. Evaporative coolers use larger volumes of air than a traditional air conditioner, so the ductwork is larger to handle the greater CFM’s.

Pacific Gas and Electric (PG&E) has a chart for sizing Energy-Efficient Ducted Evaporative Coolers for properties located in hot, dry climates (such as California Energy Commission (CEC) climate zones 11, 12 or 13, the Central Valley) and if your home was 1,250 Ft2, this would require a 5,000 CFM unit. This equals 4 CFM/Ft2. These values are based on 8-foot ceilings.

You can see that in the zones with an Average Climate a design of 3 CFM/Ft2 was used, while a Hot dry Climate is designed using 4 CFM/Ft2

Consult with an evaporative cooler supplier for the correct size for your application.

Airflow Strategies

Do evaporative coolers need to be vented? Yes, there should be a path provided for the large volume of air that is coming into the building. The air must go somewhere, so its imperative that you control the path of air to achieve the cooling results you’re looking for.

There are several strategies for providing proper airflow within the building served by an evaporative cooler.

Vents can be provided in the ceiling that allow hot air to escape the rooms as the new cooler air enters. These ceiling vents would exhaust into the attic space, thereby requiring the attic to be vented.

Evaporative Cooler Exhaust Vent Openings - Using Attic Vents — Evaporative Cooler Exhaust Vent Openings – Using Attic Vents

Venting into the attic also helps reduce attic temperatures which contributes to the overall objective of a cooler occupied space. Venting eliminates the security risk of having to leave the windows and doors open as used in the next strategy.

Leaving the windows slightly open allows the warmer air to escape the room as the evaporative cooler brings in 100% outdoor air. There is no recirculation of air through the system, as there is with an air conditioning system.

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Evaporative Cooler Air Strategies - Leaving Windows Open to Control Air Flow — Evaporative Cooler Air Strategies – Leaving Windows Open to Control Air Flow

With evaporative cooling it’s important to allow warm air to escape. This will help remove the heat from the space and avoid excessive moisture from accumulating in the building. Traditional air conditioners recirculate the air within the space and work best with all windows closed and a tightly sealed structure.

To control the flow of air within a home, it is recommended to strategically open certain windows to direct air movement. Avoid opening windows on the windward side, to avoid additional hot air from entering the space. Cracking open the windows on the leeward side of the building will allow for the warm air to escape. Avoid opening them too wide as hot air will enter the space, while not opening them wide enough will cause moisture to buildup in the space. Experiment with various openings to see how the air flows, while keeping windows closed in unoccupied rooms.

How Evaporative Coolers Work

The pump that is sitting in the water reservoir pulls water in and then sprays it over the media pads located on the side panels of the cooler, while the fan draws in hot dry air over the wet pads. The pump keeps the pads wet as the warm air travels through them, causing water to evaporative.

When water evaporates and turns into a gas it cools the dry air entering the cooler. As water evaporates and the water level in the pan begins to drop, it will activate the float valve, which will allow water into the pan until the float valve shuts off the makeup water.

The controller can be used to increase the fan speed on hot days from low to high, and or on mild days to fan only. A thermostat can be used to automatically turn the cooler on when a certain temperature is reached within the space, or a manually operated controller could be used. The thermostat can also start the water pump before the fan to ensure the pads are wet before hot dry air is brought in over them.

Evaporative coolers usually allow for several fan speeds and a fan only option. It should allow the water pump to be shutoff and only the fan to run to circulate air. Without the pump running, no water will be sprayed over the pads and the air will not be humidified. This works in mild weather or at night when less cooling is required. The fan only option allows for its use like a whole-house fan.

The evaporative cooler uses water for cooling while the traditional air conditioner uses refrigerant.

Remember that heat moves from a warmer substance to a cooler one, so the warm air is cooled down while the water absorbs some of the air’s heat, causing some of the water to evaporate. This drives the dry bulb temperature of the incoming air down, while increasing the wet bulb temperature and humidity level of the air entering the room.

As the heat from the air is absorbed by the water the sensible temperature of the air is lowered while its latent heat content or moisture level is increased. This raises the relative humidity of the space as this air is directly ducted into the space to be cooled.

Each side of a roof mounted evaporative cooler should easily have removal side panels for ease of media replacement.

Checkout these Evaporative Coolers here

Evaporative Coolers vs Air Conditioning

Evaporative coolers are much less expensive to purchase and operate than the convention air conditioner, as there is no compressor or condenser fan. The evaporative cooler uses just a fan and small water circulating pump. Since water is the basis of the cooling effect, they work best in low humidity areas.

Evaporative coolers are used for temperature reduction and humidification. There are two basic configurations, direct and indirect evaporative cooling. With a direct evaporative cooler, the air comes in direct contact with the water, as opposed to the indirect evaporative cooler where the water and air stream don’t meet each other.

With evaporative coolers there is less energy consumed then a traditional air conditioner, as the evaporative cooler only has a pump and fan that consumes energy. There is the use of water that needs to be considered.

With the use of direct evaporative cooling the water meets the air provided to the space, giving the air a filtering effect. The washing of the air can remove dust, smoke, and particles from the air stream, much like a scrubber.

When using wetted surfaces or evaporative media pads, they should be made of materials that will prevent corrosion. The use of aluminum or stainless-steel helps prevent corrosion.

Where do Evaporative Cooler Work Best

Evaporative coolers work best in dry, low wet bulb, and low relative humidity areas, as the results of the cooling effect are the based on the difference between the dry bulb and wet bulb of the entering air. The dry bub temperature can’t be reduced lower than the wet bulb temperature, so this limits the amount of cooling.

When the dry bulb temperature reaches the wet bulb temperature, the air is totally saturated with moisture. In high humidity climates evaporative coolers don’t work as well because they use evaporation as the process for cooling. Evaporation works best in low humidity regions. High humidity regions should use traditional air conditioners.

How do Evaporative Coolers Work

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