Best way to Control the second stage

Discussion in 'General Discussions' started by SolarPower, Dec 27, 2018.

  1. SolarPower

    SolarPower Member

    I have a Geologix basically (climitemaster tranquility 30) 3 ton with two way iGate thermostat

    My system is a two-stage system. I connected up energy monitoring yesterday and determined that my second stage was kicking in before it gave the first stage a real chance.

    I changed my thermostat to differential first stage 1 degree and second stage 3 degrees. Reading the manual, the second stage would not come on until 4 degrees from set point with these settings.

    This is my first two stage system. How do others have this setup?

    Does it sound like I am on the right track or is there a better way?
     
  2. geoxne

    geoxne Active Member Forum Leader

    There is no real reason to retard 2nd stage. Published efficiency for first stage is overstated with EWT is 9F degrees higher. This does not happen in real world conditions. Given the same EWT 1st stage is only slightly more efficient.

    Set your second stage differential to what ever makes you comfortable. My wife would never tolerate a 4F degree droop from setpoint at the thermostat.
     
  3. SolarPower

    SolarPower Member

    Good point 4 degrees is probably to much.

    I changed it to 3 degrees to kick in second stage. We will see how that works.
     
  4. ChrisJ

    ChrisJ Active Member Forum Leader

    I have not had that issue, (I have basically the same heat pump), I didn't want second stage at all, I locked it out with the "demand reduction" feature.

    I don't think you have to go as far as 3 degrees.
     
  5. SolarPower

    SolarPower Member

    You only run the first stage?
     
  6. nc73

    nc73 Member Forum Leader

    Kind of a waste...single stage heat pumps are much cheaper.
     
  7. ChrisJ

    ChrisJ Active Member Forum Leader

    Yes, my house turned out to have a much lower load then the manual J said. Not complaining... Probably should have gotten a 2 ton, 2 stage.

    I just started using the program feature of the tstat, I was always a set it and forget it guy. I set back 3 degrees from 70*F to 67*F mid morning and overnight.

    What happened at first was the heat pump went to second stage right away and didn't down stage till call was satisfied. I decided to try locking out second stage, at 4:00am letting the HP run for hours and bring temp up slowly. That allowed the desuperheater to get my storage tank up over 100*F.

    When winter really hits I may have to adjust the tstat. I can let it run stage 2 for an hour or so, then lock out after that.

    I have no toaster strips, my design day temp is 0*F, I know I will have to unlock 2nd stage when we get a cold snap of single digets or negative numbers.

    A lesson learned too late. Manual J load cals usually put a heavy thumb on the scale. We used open cell spray foam when building the house in 2009, the building inspector insisted on a vapor barrier so the whole inside got covered in poly. Turned out to be very air tight.
     
  8. nc73

    nc73 Member Forum Leader

    I'm thinking of doing spray foam too when I renovate. Once improved I will probably be oversized, but oh well. Right now it's sized just right.
     
  9. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    We usually set it to 0.5 F, 1F and 2F for first, second and aux heat, respectively. There is really no good reason not to let the second stage come on earlier. The compressor will not use much more power, but pumping and fan power go up higher proportionally. But stage 2 running is relative rare, usually around 10-15%. Unless you setback.
     
  10. SolarPower

    SolarPower Member

    Thanks for the replies.
    I changed it to first stage 1 degree second stage will be 2 degrees.
    Thanks again for the advice.
     
  11. Ralph302

    Ralph302 New Member

    How did those settings work for you? I also have a TE-30 (5ton) and it seems mine too goes right to stage 2 before giving stage 1 a chance.
     
  12. SolarPower

    SolarPower Member

    I changed the thermostat to differential first stage 1 degree and second stage 1 degree.
    Second stage will not kick in until it is 2 degrees from set point. This is working well for us. The stock setting the second stage kicked on so much more it did not give the first stage a chance.

    I am running the OEM thermostat with igate.
     
  13. Ralph302

    Ralph302 New Member

    So you changed the Temperature Algorithm from the default of 'Proportional Integral' to 'Differential' then set the Differential to 1 for Stage 1 and 1 for stage 2.
     
  14. SolarPower

    SolarPower Member

    Yes that is exactly what I did. Now stage 2 only runs when needed. Stage one runs most of the time. Only on really cold nights does it ask for stage 2.
     
  15. Ralph302

    Ralph302 New Member

    Thanks, I'll give that a try.. Last electric bill was shocking !
     
  16. Ralph302

    Ralph302 New Member

    That seems to be the ticket ! Have you ever messed with the the 'Delta T' settings?
     
  17. SolarPower

    SolarPower Member

    I have an external pump with a three-speed pump. I have it on high for the winter. In the summer I will check in medium will be enough.
    The Delta T setting is for internal pump from what I read.

    Keep in mind I am just a DIY home owner not a pro like some on here.
     
  18. Ralph302

    Ralph302 New Member

    Thanks, I'm a newbie just trying to learn. So all advise is welcome. I believe a higher pump speed would lower the Delta T and a slower speed would raise it. I tried setting a higher Delta T (11) and my pump's GPM was way down as was it's wattage, but so was the leaving air temp (mid 80's). At a lower Delta T (5 or 6) the pump's GPM goes up (wattage too) and the leaving air temp is up (low 90's). Just trying to find that happy median !
     

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