TMC Home  
Trevor-Martin Corporation 
Pool Heaters
Heat Recovery
Common Questions
Commercial Units
Hydronic Heating
HW Generator
HW Generator
Electrostatic Filters
Dust Eliminator

Heat Recovery Units
Frequently Asked Questions (FAQ)

Why is Heat Recovery good for you?
      You get free hot water every time you use your Air Conditioner or Heat Pump.  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.  That saves you energy and money too!

How much can I save?
      The Electric Company projects the utility bill savings!  Florida Power says, "An average family can save up to 50% on annual water heating cost."  In addition, the improved cooling performance from your air conditioner or heat pump means even more savings on your utility bill.

Your actual savings depends on several factors.  They include:

  1. How many people live in your house
  2. How much hot water you use every day
  3. What time of day you use your hot water
  4. How much your Electric Company charges per kilowatt hour
  5. How long your air conditioner or heat pump runs each day
  6. How big and how efficient are your air conditioner, heat pump and water heater tank

     As you can see, the number of factors and their interaction make it very difficult to precisely predict the actual cost savings, but we have compiled the results from actual home installations to come up with typical costs and savings.

     To get an idea of the approximate savings you can expect from your Heat Recover Unit, use tables 1 and 2 to estimate the water heating savings and air conditioning performance improvement savings.

Table 1:
Table 2:
Annual Water Heating Cost
At Various rates per KwH
8.0¢ 8.5¢ 9.0¢ 9.5¢ 10.0¢

40 gal.

$239 $254 $269 $284 $299
3 55 gal. $329 $350 $370 $391 $412
4 70 gal. $419 $445 $471 $498 $524
5 85 gal. $509 $541 $572 $604 $636
6 100 ga. $599 $636 $673 $711 $748

     The annual cost includes both heating up cold water to replace the hot water you use and the loss of heat from your water heater and piping between your uses of hot water.
      Calculate the savings by multiplying the annual cost figure from the table by the fraction of the year that you operate your air conditioning (i.e. 6/12 or 8/12 or 4/12 etc.)

Monthly Savings at
various rates per KwH
8.0¢ 9.0¢ 10.0¢
3 Ton $11.50 $13.00 $14.50
4 Ton $15.50 $17.50 $19.50
5 Ton $19.50 $22.00 $24.50

      The table assumes 8 hours of air conditioning per day on a SEER 9 unit, and sufficient hot water usage to keep the heat recover unit running.  Older, less efficient units will increase the rate of monthly savings.  The newest super-high efficiency units will tend to reduce the savings.
      Calculate the savings by multiplying the monthly figure from the table by the number of months per year that you run your air conditioning.

PAYBACK EXAMPLE - For a family of 4 with a 3 ton A/C, 6 months of cooling and 9.0¢ per KwH electricity in 1998.

Average installed cost of Heat Recovery
Less:  Hot Water Savings (6/12 x $471 = $235.50)
Less:  A/C Improvement Savings (6 x $13 = $78.00)
Net 1st Year Cost
PAYBACK - Less than 2 Years!!!  

How does a Heat Recovery Unit (Desuperheater) work?
     Trevor-Martin Heat Recovery Units are hooked up to both your air conditioner and water heater.  They recover the waste heat discharged from the refrigerant cycle of your air conditioner and transfer that heat to the water in the water heater.  In effect, it turns hot air that would otherwise be wasted by your air conditioner into free hot water.

My A/C Contractor told me that heat recovery units don't work on equipment over 12 SEER. Is this true? What about on condensers with dual compressors? How about variable speed compressors?
     Heat Recovery works by extracting heat from your refrigerant as it leaves the Air Conditioner or Heat Pump compressor and transferring the heat into your water heater. The more efficient, high SEER models run with lower hot refrigerant temperatures so they don't heat water as fast as the lower SEER models. However, as long as the refrigerant temperatures are over 130° F, you can transfer heat back to the water heater. So, while it's true that a 13 SEER air conditioner doesn't make as much hot water as a 10 SEER air conditioner, it is incorrect to say that heat recovery does not work. Generally speaking, you need to get above 14 SEER before you even have to worry about the hot refrigerant temperature being too low to enable the heat recovery to work.
     The question to ask, regardless of whether you have a single, dual or variable compressor is how hot does the refrigerant get? Anything over 130° F will work.

I heard that Heat Recovery Units will decrease the efficiency of my air conditioning system. Is this true?
     Absolutely not!! As a rule of thumb, a Heat Recovery Unite will increase your A/C efficiency by 10%. It also reduces the head pressure on the compressor; thereby reducing stress and improving compressor service life.
     You get three benefits from adding a heat recovery: Free hot water for your house; reduced air conditioning cost; and improved A/C operating life.

Will a Heat Recovery Unit void my warranty on either the A/C system or the water heater?
     It's been more than 25 years since the first Heat Recovery Units were produced and installed on residential air conditioners but, even now, about twice a year we hear from someone who says that their A/C Contractor claims that it will void the warranty if they add a Heat Recovery Unit to their A/C. Each time we hear this, we investigate. We have never been able to find any written confirmation nor corporate representative willing to support the claim. Our Heat Recovery Units are sold directly to Carrier, Trane, Lennox, Goodman, and most other brands for use with their own equipment. We also sell to nearly every major national distributor of HVAC components and systems.
     Of course, all units must be installed by licensed contractors according to the provided installation instructions.

My A/C installer tells me that Heat Recovery Units (Desuperheaters) do not work with XXXXX brand air conditioning systems. Which brands are ok to use?
     Any air conditioner or heat pump that produces hot refrigerant at temperatures above 130° F as the gas leaves the compressor is suitable for desuperheating; that includes models that use the new R410 refrigerant. They also work with all brands, limited only by temperatures.
     The hotter the refrigerant gets when your air conditioner is running, the more heat you can extract and turn into hot water. The higher the energy efficiency (SEER) rating, the cooler the refrigerant temperature may be, giving the Heat Recovery Unit less to work with and slowing the production of free hot water. Some super high SEER models (18 SEER and up) don't always get hot gas temperatures above 130° F. The desuperheater doesn't operate under this condition. Ask your A/C contractor about the SEER and the operating hot gas temperature of the air conditioning system that is being presented to you, so you can make your own informed decision.

What brand of Heat Recovery should I get?  Is there any difference in efficiency?
      Trevor-Martin manufactures multiple name brands of Heat Recovery Units, but there are only two distinct residential designs.  Trevor-Martin manufactures Heat Recovery Units for both residential (up to 5 tons) and commercial applications (up to 200 tons).
      All models for residential use are comparable in efficiency and have similar optional components available to them.  No matter which brand name you choose, all Trevor-Martin Heat Recovery Units will serve you well for years to come. 

What options are available for the units? What do the letters at the end of the model number mean?
      -V ...  Hand valves with drain. Used to bleed air from the system to prevent circulator pump from becoming air-bound. Also used to stop water flow to the system for servicing as well as allowing the system to be drained during extended periods of freezing temperatures.
      -PC ... (Aquefier) Hand valves with drain and pressure relief valve. Required to meet some county's building codes.
      -VP ... (All Others) Hand valves with drain and pressure relief valve. Required to meet some county's building codes.
      -M ...  Mixing Valve (Tempering Valve). Recommended for units 13 SEER and over but works fine with those rated lower. Holds water in the heat exchanger until desired temperature is reached. Although adjustable, keep valve set to 120° F (lowest setting).
      -F ...  Freeze Protection. Unit contains a thermostat to activate the water pump when ambient temperatures fall below 40F. Helps to protect unit during short periods of freezing temperatures.
      -410 ... Certified for use with R410A (Puron) systems. Currently available in Aquefier brand models only.



  Copyright © 2001-2002 Trevor-Martin Corporation,  All Rights Reserved
Contact Information