How To Look At A House

McGarry and Madsen's home inspection blog for buyers of  

site-built, mobile/manufactured and modular homes

What is an air conditioning heat recovery system?

Saturday, August 4, 2018

An air conditioning or heat pump system cools your house during the warm months of the year by absorbing the heat from the interior and transferring it outside. If you put your hand over the top of a condenser (outside unit) while it is operating, you will feel the hot air being blown upward as heat is dissipated from the condenser coils that encircle the outside of the unit. 

   A heat recovery system connects between the your water heater and air conditioning or heat pump condenser, transferring some of the heat into the water heater tank that would ordinarily be exhausted into the atmosphere. It is essentially a heat interface between the “hot” pressure line of the air conditioner and a loop of water pipe connected to the water heater, and can provide savings of up to 50% on your hot water energy cost in areas like Florida that have a long air conditioning season. 

  “You get free hot water every time you use your air conditioner or heat pump,” according to one manufacturer, Trevor-Martin Corporation. “That saves you energy and money every month. Plus, your air conditioner or heat pump cools more efficiently every time your heat recovery unit runs.”

   The unit itself is a metal box that is located next to either the water heater (inside) or the air conditioning condenser (outside). The box will usually state that it’s a thermal recovery unit, but sometimes the markings will be faded away or missing—especially if it is outside next to the condenser.

   Even without any markings on the box, you can identify it as a heat recovery system by observing the extra insulated pipes connected from it to the condenser and water heater. Here’s an example below.

And here’s several examples of the different brands of units, with the last one being of a pair of older units behind their respective condensers, with markings that have been worn off by the weather. 

   To learn more about heat recovery systems, we suggest you visit the Q&A page of Trevor-Martin Corporation at; or, for a more detailed explanation of thermal recovery systems, download a technical paper by Ronald Jarnigan, of University of Florida Cooperative Extension Service, by clicking the link below.


    Also, see our bog post What does a "heat pipe" do in an air conditioning air handler?

• • • • • • • • • • • • • • • • • • • • • • • • • • • • 

  To learn more about heating and air conditioning systems, see these other blog posts:

How can I find out the SEER of my air conditioner? 

My air conditioner won't turn on. What's wrong? 

How can I find out the size of my air conditioner? 

How can I tell whether the condenser (outdoor unit) is an air conditioner or heat pump? 

Where is the air filter for my central air conditioner and furnace? I can’t find it? 

Does an old air conditioner use more electricity as it ages? 

How did homes stay cool in Florida before air conditioning? 

What is wrong with an air conditioner when the air flow out of the vents is low?

Why has the thermostat screen gone blank? 

Why does it take so long to cool a house when an air conditioner has been off for a while? 

Why is my air conditioner not cooling enough? 

What are the most common problems with wall/window air conditioners?  

Will closing doors reduce my heating and cooling costs? 

    Visit our HEATING AND AIR CONDITIONING  and WATER HEATERS pages for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.

Water Heaters

Water Heater Age

"What Are The

Signs Of..."

Septic Tank Systems

Structure and Rooms

Plumbing Pipes

Termites, Wood Rot

& Pests



When It First

Became Code

"Should I Buy A..."

Park Model Homes


Shingle Roofs




Wind Mitigation

Roof and Attic

"Does A Home


Pool and Spa

"What Is The Difference Between..."




Concrete and

Concrete Block

Metal Roofs


Modular Homes

Rain Gutters

Mold, Lead & Other Contaminants


Older and

Historic Houses

Crawl Spaces

Mobile-Manufactured Homes

Building Permits

Life Expectancy

Clay Soil





Exterior Walls

& Structures


Common Problems

HUD-Code for

Mobile Homes

Garages and Carports

Flat (Low Slope) Roofs

Electrical Panels

Sprinkler Systems

Electrical Receptacle Outlets

4-Point Inspections

Hurricane Resistance

Frequently Asked Questions (FAQ)

Home Inspection

Heating and Air Conditioning

Building Codes

Fireplaces and Chimneys

Inspector Licensing

& Standards

Energy Efficiency

Washers and Dryers



Doors and Windows



Electrical Wiring

Click Below  

for Links

to Collections

of Blog Posts

by Subject

Plumbing Drains

and Traps


Smoke & CO Alarms

Aging in Place

Top 5 results given instantly.

Click on magnifying glass

for all search results.






Air Conditioner & Furnace Age/Size


Electrical Switches





Water Intrusion

Electrical - Old

and Obsolete


Foundation Certifications

Tiny Houses

About McGarry and Madsen



Buying a home in North/Central Florida? Check our price for a  team inspection by two FL-licensed contractors and inspectors. Over 8,500 inspections completed in 20+ years. In a hurry? We will get it done for you.

Moisture Problems

Crawl Spaces