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.

Install high efficiency heat pump as primary heat do i have to change control board?

oakland Member Posts: 23
I currently have a oil fired Lennox furnace with a 5 ton central AC unit that is about 11 years old that share the blower. I want to change out the AC with a high efficiency Goodman heat pump and make the oil furnace the back-up. I know i have to change the indoor coil and the blower i have make variable speed. Do I have to change the control board and if so to what model?


  • heatpro02920
    heatpro02920 Member Posts: 991
    edited March 2014

    You can do this with a thermostat, have your hvac contractor give you the options he is comfortable with that will work for aux heating... Not sure what climate you are in but up here heat pumps are good for some of our season not the entire season, so I usually wire them in with an out door temp sensor so the primary heat kicks in at the temperature the heat pump is more expensive to operate...

    I have used the nest to do this if you are comfortable with that option... but there are many out there...

    nest has a balance feature http://support.nest.com/article/What-is-Heat-Pump-Balance
  • oakland
    oakland Member Posts: 23
    schematic of wires going to and from the control and thermostat

    Thank you. I live in a northern zone climate. My original set up only included a Lennox furnace for heat and a 5 ton AC for air cond. and now I am adding a heat pump. Where do the new wires for the heat pump get connected to? How does the blower know when to come on for the heat pump? Maybe I should be asking for a schematic diagram of the wires going to and from the control boards and thermostat.Thank you
  • heatpro02920
    heatpro02920 Member Posts: 991
    new wires

    your contractor is going to know how to wire it, but to answer your questions...

    The fan is going to come on the same way it does with your A/c, through the fan center control, the thermostat is going to tell the outdoor unit what to do {control the reversing valve from heat to cool}...

    when I do an install like what you are describing, I change the tstat, tstat wire and wire going to the outdoor unit. You can use a dual fuel control too they are very affordable, here are some diagrams that may help you understand..

  • oakland
    oakland Member Posts: 23
    controls allow blower to be variable and take advantage of 2 stage heat pump

    Heatpro I believe the present control has three speeds and with the new controls are we able to make the fan variable speed and take advantage of the two stages of a high efficiency heat pump. thanks again