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  1. #14
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    Mar 2013
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    112
    Yes, I agree and from all I have read about it and from what most are saying in here is would be a great system to have.

    Thanks

  2. #15
    Join Date
    Nov 2004
    Location
    SW FL
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    6,295
    What size equipment do you need when the daily Low is 20'F and the high 8 hours later is 50'F?
    IN- Out T
    70-20 = 50'F dT 6 am
    70-50 = 20'F dT 2 pm
    So, heat loss for dT 6 am will be about 2.5 X heat loss for dT 2 pm

    Is your Design Temperature which is used for sizing equipment going to be 35'F?
    Is an inside temperature swing of nearly 20'F acceptable?
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  3. #16
    Join Date
    Mar 2013
    Posts
    112

    Desine temperature used

    Quote Originally Posted by dan sw fl View Post
    What size equipment do you need when the daily Low is 20'F and the high 8 hours later is 50'F?
    IN- Out T
    70-20 = 50'F dT 6 am
    70-50 = 20'F dT 2 pm
    So, heat loss for dT 6 am will be about 2.5 X heat loss for dT 2 pm

    Is your Design Temperature which is used for sizing equipment going to be 35'F?
    Is an inside temperature swing of nearly 20'F acceptable?
    I used dT of 65F or 36C for the caculation. This is the worse case scenerio. The guy who said i needed a 3 ton used dT of 65F. I should not need this amount ever. We do not have 30 degree temperature swings here?

    Jimmy
    Last edited by JimmyP; 04-17-2013 at 10:41 AM. Reason: mistake

  4. #17
    Join Date
    Mar 2013
    Posts
    112
    Dan

    For dT of 50F I need 16382 BTU's/hr and for dT of 20F I need 6553 BTU's /hr

  5. #18
    Join Date
    Mar 2013
    Posts
    112
    Dan

    HDD's used in caculation from Dec2012-March2013 was 2395C or 4311F.
    coldest average low temperature seen here was 15F or -9.3C dT of 55F and for that I need 18020 BTU's /hr based on usage over that time period.

    Jimmy

  6. #19
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    Just realize that if if the delta T goes to 65F for more than a couple hours your hosue may start to cool off. It's possible that in a cold snap, it could sustain a 50F delta T for more than 24 hours, so you home may cool down to 60-65F. If that's acceptable or you plan to have a supplemental heat source like a small wood stove or direct vent fireplace, then you'll be fine.

  7. #20
    Join Date
    Mar 2013
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    112
    Quote Originally Posted by motoguy128 View Post
    Just realize that if if the delta T goes to 65F for more than a couple hours your hosue may start to cool off. It's possible that in a cold snap, it could sustain a 50F delta T for more than 24 hours, so you home may cool down to 60-65F. If that's acceptable or you plan to have a supplemental heat source like a small wood stove or direct vent fireplace, then you'll be fine.
    Thanks for that information.

    I do have 2 directvent fireplaces installed. One in the basement and one on main floor in the living room. So I would be ok. If it does get down to 5F it would only happen for one or 2 days a year. the average low in the winter is 15F while the ave daily temp is 25F.

  8. #21
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    IF you hame has a lot of thermal mass and you use those firepalces on teh coldest days, then sizing for a lower desing delta T isn't a bad idea. Or... you do your load calculation for the full design conditions, then factor in your supplemental heat source.

    Infinity control with their integrated HRV isn't a bad way to go. Single controller all in one, and it will manage humidity levels and you can lock out aux heat strips above certain temperatures. thsi woudl allow you to use setbacks in some conditions. Also there is some logic to recover from a setback over a 90 minute period to avoid using back-up heat.


    FWIM, I've had my new Infinity 19 for 3 days now. Super, super quiet. You can't hear it even on a quiet morniing standing 20' away. Just a very slight hum from the compressor vibration. I might add some rubber washers to isolate the lineset better (yes, I'm a little too particular). At 20F, the integrated capacity of the Infinity 19, 2 ton is 15k BTU. COP is 2.7 at that temp. With 2000BTU of strip heat, that's a COP of 2.5. The Greenspeed does not need heatstrips, but would only be runing at about 50% load, with a COP of around 2.7. If you needed the full 24k BTU's @ 20F, the Greenspeed would have a COP of about 2.6 and the Infinity 19 drops to a combined COP of 1.8. Follow that?

    Bottom line, because you don't need the full nominal capacity of the heat pump, a Greenspeed might not have that large of a benefit in energy savings. But it will offer more comfort. Both are very quiet.

    If those fireplaces are natural gas, depending on your rates, they are probably cheaper to run below 20-30F than either heat pump anyway. IF propane, you just as well using heat strips, the cost is about the same.

  9. #22
    Join Date
    Mar 2013
    Posts
    112
    Motoguy

    They are propane and we are in a remote area that they only deliver 2 twice a year. It is ideal for when we have power outages in the winter. Would the 3 ton infinity be to oversized for cooling in low stage? Do you have performance data for the infinity 19?

    Thanks

  10. #23
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    Do a google search for Carrier 25HNB9 product data. There's also the HNA6.

    What was your calculated heat gain? The 3 ton will need 50% larger ductwork & airlfow. The 3 ton would be oversized in cooling, but since humidty control probably isn't an issue there it might not be a problem. I thought you said you hardly use cooling.

    By the time you've increased the ductwork size and added more registers, etc. you might as well go with the 2 ton Greenspeed. The heat capacity of the greenspeed at 17F is almost equal to a 4 ton standard heat pump.

  11. #24
    Join Date
    Mar 2013
    Posts
    112
    Quote Originally Posted by motoguy128 View Post
    Do a google search for Carrier 25HNB9 product data. There's also the HNA6.

    What was your calculated heat gain? The 3 ton will need 50% larger ductwork & airlfow. The 3 ton would be oversized in cooling, but since humidty control probably isn't an issue there it might not be a problem. I thought you said you hardly use cooling.

    By the time you've increased the ductwork size and added more registers, etc. you might as well go with the 2 ton Greenspeed. The heat capacity of the greenspeed at 17F is almost equal to a 4 ton standard heat pump.
    Thanks

    I did find the data.

    We only have about 60 cooling degree days a year but with all the windows we have I could use some AC if I have it.
    My heat gain was about 21000 btu's I think I don't have the numbers with me
    Last edited by JimmyP; 04-17-2013 at 06:51 PM. Reason: spelling

  12. #25
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    60...? Don't worry about being oversized. It won't matter. I now understand why they selected 3 ton. It might be a better way to go to start off the heat strips. You may still want 5 or 7kw just for defrost and for backup. But you can disable them over 20f otherwise.


    Sent from my SGPT12 using Tapatalk 2

  13. #26
    Join Date
    Mar 2013
    Posts
    112
    Quote Originally Posted by motoguy128 View Post
    60...? Don't worry about being oversized. It won't matter. I now understand why they selected 3 ton. It might be a better way to go to start off the heat strips. You may still want 5 or 7kw just for defrost and for backup. But you can disable them over 20f otherwise.


    Sent from my SGPT12 using Tapatalk 2
    I know not much need for AC. What do you mean to start off the heat strips?

    I guess with the 3 ton you would still get enough heat at the lower temperatures. So there would be no need for a 2 stage either then?

    Jimmy

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