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High efficiengy heat pump connected to a single stage blower

I have a high efficiency 2 stage compressor variable speed capable heat pump but i only have a single speed blower on a oil fired Lennox elite series hot air furnace which I want to use as back-up heat. Can I connect the high efficiency heat pump to the single stage blower? I know I wont get the same efficiency, but will it work? I do not have enough volts in basement to put in a air handler with heat strips?


  • SpenceSpence Member Posts: 316
    2-stage HP

    Can you connect to a single speed blower? Yes. Is it a good idea? No. You'll have to hook up Y2, losing the 1st stage and the benefits therein.
  • oaklandoakland Member Posts: 23
    do i have to change control board?

    Thanks. I found that i could attach a retrofit motor to make the blower multi speed to take advantage of the heat pump stages. Do i have to change the control board to make the goodman heat pump the primary source of heat and the oil fired lennox elite series furnace as back-up? I want to use the furnaces blower to move the heat around for the heat pump and furnace. Thanks all responses would be appreciated.
  • oaklandoakland Member Posts: 23
    the system also has central ac unit

    the system also has central ac unit which i will changing out with the goodman heat pump.
  • SpenceSpence Member Posts: 316
    2-stage HP

    You're better off using a single stage heat pump with your existing furnace.
  • edited March 2014
    Single stage heat pump

    I think  it will not work. Try to used a single stage heat pump.
  • oaklandoakland Member Posts: 23
    What is y2?

    Spence what is a Y2 and how will I lose the 1st stage? Thank you
  • SpenceSpence Member Posts: 316

    This is your second stage cooling signal from the comfort control. There are a litany of reasons why you need an AHRI matched system; efficiency, performance, and comfort are just a few. Understand that when the CC calls for 2nd stage, the blower and outdoor fan ramp up to match the higher compressor output, so without this feature you have wasted a bucketload of cash in a two-stage HP that will never live up to expectations.
  • SpenceSpence Member Posts: 316
    Evergreen ECM

    Fantastic motor, yet not intended for 2-stage applications.
  • BusterBuster Member Posts: 30
    edited March 2014
    2 Stage

    I don't know why you would say that, any multi-speed motor is designed for multi-stage operation and an ECM motor is the best at it! The Evergreen can run at 4 different speeds on one system.
  • oaklandoakland Member Posts: 23
    which speeds settings do i use for the back-up furnace, heat pump and AC?

    Thanks everyone for your help. If I go with the one stage heat pump my blower has a least 3 set speed settings slow, med and high i believe which speed do i use for the back-up furnace, primary heat pump and air conditioner?
  • SpenceSpence Member Posts: 316
    Blower Speeds

    By default, the thermostat signal for compressor operation (Y) goes to the highest speed you have set. The heat pump is "stupid" as it doesn't know if it's heating or cooling; that's the reversing valve's job, so you get the same speed both summer and winter. Depending on when you're in restricted mode, your furnace will operate on the heating speed set by you or the factory setting if you haven't changed it.
  • SpenceSpence Member Posts: 316

    It's not the motor; it's the control system that stages speeds. The Evergreen does have speed taps, yet only one can be used at a time. It doesn't jump from tap to tap. You would have to have a variable speed ECM to do that.
  • oaklandoakland Member Posts: 23
    I probably going with the single stage but if i went with the two stage heat pump

    One last question and thanks everyone for your help. I know I said I was going with the single stage heat pump, but if I did go with the two stage heat pump could i not set the lower stage to the lower blower speed(Y1) and higher stage to the higher blower speed(Y2) and the furnace would go to the factory default. The thermostat would detect that the heat was struggling in lower stage and kick in higher stage and then at lets say 20 F the heat pump would shut down and the oil furnace would kick in?
  • SpenceSpence Member Posts: 316
    2-stage Response

    No. The Y circuit is the compressor contactor. The comfort control simultaneously makes contact to the fan circuit (G). What you're missing (see earlier posts) is the two compressor signals from Y and Y2, or similar markings, such as Y1, YLO, etc. This control scheme has to be built in to achieve your certifications and ratings.
  • oaklandoakland Member Posts: 23
    I understand it better and going with single stage

    Ok - I understand it better. Thanks Spence and everybody for your help. I will be going with the single stage 16 SEER and I'm sure I will be saving quite a bit as I try not to use heating oil as much as I can.
  • SpenceSpence Member Posts: 316
    HP Savings

    On behalf of all of us, you are most welcome! What is the HSPF of your unit choice? Just landing on a SEER rating says nothing about heating. Then you have two balance points to consider; economic and thermal, so you can optimize the hidden benefits of your heat pump. You have a little work yet to do, and we will help you through it. This is the fun stuff!
  • oaklandoakland Member Posts: 23
    I chose a Goodman heat pump 9.5 HSPF, 16 seer, 5 ton

    The unit I chose was a Goodman heat pump 9.5 HSPF, 16 seer, 5 ton, single stage unit. I did a heat loss calculation and I got numbers of about ~40,000 btu heat loss, ~68,000 btu input and ~54,000 btu output. These are rough figures because i dont have the paper work in front of me. The central AC only that is on there now is a 5 ton unit. The indoor coil they put on for the AC is a 10 seer I will be putting on a new one for a 16 seer unit. Did this size coil match the oil furnace i have? Or it does not matter and it has to match the AC?  Does this sound good?
  • SpenceSpence Member Posts: 316
    Heat Pump Sizing

    First of all, you need to size your heat pump for the cooling load, not heating. In the winter the HP has support from your oil furnace. You won't dehumidify in the summer sizing to your heat loss. You need a factory match with your ID and OD coils, as well as tubing. How did you end up with a huge cooling size (5-tons) if your heat loss is only 40,000 BTUH?
  • oaklandoakland Member Posts: 23
    sizing up the heat pump

    This what i calculated but i am not sure how accurate it is for 2,200 sq/ft heated living space in a house built in 2003: building envelope = 32,000 btu/hr, infiltration heat loss = 8,737 total loss = 40,741 btu/hr. altitude deration output= 50,926, and efficiency deration total input. Which number do you go by? I understand to that everything has to match. I want the heat pump to heat well since i am in the Northern climate so i should lean to the heating side not so much the cooling.
  • SpenceSpence Member Posts: 316

    NEVER size a HP to heating! Your load should be one BTUH value based on weather station, building materials, glazing, insulation, doors, walls, roof, etc. What load calculation program are you using?
  • oaklandoakland Member Posts: 23
    Pikes Peak heat loss table

    I am using the pikes peak regional building dept. heat loss calculation table. One of the only ones i could find for free. Also, i was tearing away some insulation and it state heat pump on my cased coil and I am trying to find out if it is for 5 ton heat pump. If I could find a heat pump possible 8.5 to 9.5 hspf, 410 , compatible with my PCM motor and have the lines cleaned of r-22 would that be the way to go? or should i just put in a 13 seer r-22 5 ton heat pump? The coil model # is c-23-51/65. The lennox series elite oil furnace model number is 023Q5-140/154A. The blower motor part #is 33H45. Thanks
  • SpenceSpence Member Posts: 316
    Pikes Peak

    I have some real and deep concerns for you. Some regional "magic numbers" don't address your house, which, as do you, has it's own "personality." For example, just one 3' x 4' window of reasonable quality can raise your summer load by almost 500 BTUH. Tell me how magic numbers show house details! We need to do a proper load; I will be happy to run one for you. I will need a bucketload of info, so you can ping me directly if you want.

    Don't fall for the R-22 trap, and NEVER use an existing coil, unless five years old or less and is an APPROVED match after a TXV swap!
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