Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Dual Fuel systems (heat-pump w/ Fossil Fuel)

As stated before, finding the balance point is critical. This is the point at which the heat pump no longer produces enough btu to satisfy the load on the structure. We sell a modulating plenum heater that we install above the a-coil that assists the heat pump down to approx 0-5 deg. We size it to handle the load in combination with the available btu from the heat pump. Usually results in approx 1.6 COP at 5 degrees fahrenheit. The plenum heaters control board and sensors take the place of an all fuel board and outdoor sensor. It also eliminates the need for a heat pump stat, as all the logic is programed in the board. The board will determine, based on plenum temp, whether or not to switch to fossil fuel or use the plenum heater and heat pump to heat down to the switch over temp you select. If the heat pump and heat strip fail or are not able to keep up, the system will automatically switch to fossil fuel.
Send me an email if you want more info on this system.


  • Jamie Pompetti_2
    Jamie Pompetti_2 Member Posts: 62

    With the increase in fossil fuel pricing we have noticed that our customers have been inquiring about dual fuel systems. We have installed quite a few of the Carrier Infinity hybrid systems. Although, they are expensenive. We are now offering lower SEER equipment also in the same package.

    The two we have installed this month we used the Honeywell 8000 touch screen, which operates the system as the manger of which systems runs, the Heat-pump or the furnace.

    This stat. allows you to lock the heat-pump out at your discretion.

    Finally the question!!!!!!!

    At what temperature are you losing ground with your heat-pump and you should allow the fossil fuel to take over?

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • Paul Fredricks_3
    Paul Fredricks_3 Member Posts: 1,557

    We always went with 40 degrees. Of course that was quite a few years ago.
  • lee_7
    lee_7 Member Posts: 458

    We always went with 35 degrees. Was always taught that between 35 and 40 degrees, there simply is not enough ambient heat to heat your home and supplemental heat would be needed.
  • Ken D.
    Ken D. Member Posts: 836
    Balance point

    Consult with the manufacturer and use your area's design temp. to determine your balance point. The equipment of today is so much more efficient they have a lower balance point than in past years. The balance point is the threshold where the heat is leaving the house at the same rate you're putting it in. Even below the BP, the heat the HP is producing is still a good buy.
  • John Mills_5
    John Mills_5 Member Posts: 950
    I usually

    set the Vision Pro 8320 to 35 out since it doesn't call for backup. I set the IAQ models to 30 and set it to call for backup if the temp drops 2°. So far no problems.

    If you are selling Trane or American-Standard units, be careful as their heating output is lower than cooling, often up to 6,000 BTU. You might have to have them changeover a bit sooner. Look at the ARI ratings.
This discussion has been closed.