Run Time

Discussion in 'Maintenance and Troubleshooting' started by BatocheBob, Nov 27, 2012.

  1. BatocheBob

    BatocheBob Member

    I'm wondering if there is a typical run time for a properly designed geothermal heat system. I appreciate that there can be any number of variables involved but lets assume the system is properly sized, the house is super insulated and the outdoor temperature is -4 Farenheit and the desired indoor temp is 70 F. My system under these conditions has been running 10 of the past 12 hours. Everytime I looked it was in Stage 1. This doesn't seem normal to me. Thanks.
     
  2. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    This depends on the original design. Our software will give an estimated run time. Don't know if all does though. But it is quite specific to your requirements (climate, house loads, loop size, etc.).

    The closer you are to your design temperature, the longer it should run.

    Yes, only running in stage 1 (assuming you have other stages) for that length of run time is a bit suspicious. Look at thermostat programming then low voltage wiring first.
     
  3. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    in theory, a properly designed system will probably run 100% of the time in second stage when the outside temperature is at or below design temp. Only the person who designed your system can tell you what the design temp is.
     
  4. BatocheBob

    BatocheBob Member

    Thanks for the quick replies. I just pulled my sheet and the outdoor design temp is -31C, ground temp of 43C and Indoor design temp of 72C. The past couple of days the outdoor tem has been -15 to -24C and I'm hard pressed to keep the house at 70C. the one thing that I'm really suspicious is my ground loops are at 10' but I'm thinking the frost line is probably already at 4' and can easily go to 6 -7' if this weather persists for another couple of weeks or more. Thanks
     
  5. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    if your system shifts to second stage, it will be better able to keep the indoor temp up.
     
  6. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    Some mixup going on with the F and C, but I can interpret:)

    Your entering water temperature would help.
     
  7. BatocheBob

    BatocheBob Member

    That was an interesting exercise. The ground loop input on the 3 ton system (basement floor heat) is 46F while the 4 ton loop (house air heat) is 40F. Thanks
     
  8. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    Define "hard pressed to keep the house at 70*".
    If you are maintaining set point running only 50 to 70% of the time in first stage within 10F of your design low then I still think your expectations are the problem here.
     
  9. BatocheBob

    BatocheBob Member

    Thanks for your input. I do agree that expectations play a big part and that is the point of this exercise. You may be correct and my expectations may be out of line and if so I'll accept that.

    'hard pressed' was a term I coined in response to the amount of time it takes the system to recover the one degree drop in temperature and the system does eventually restore the set point. yesterday between 4;00AM and 4:AM this morning the system ran 20 hrs. out of 24 hrs. I will admit that the house is staying nice and warm in spite of the outdoor temp and our operating cost i.e. power consumption does appear to be at a reasonable level although I would not say that we are realizing the 60 - 75% savings that is mentioned in most vendor literature. When comparing to others with similar houses I figure we are saving about 20%. This is why I am wondering if we should not be achieving greater savings if we where running less time. keep in mind that according to the specs I have the system was designed for a outdoor temp of -31F, an indoor temp of 72F and a mean soil temp of 42F. Our outdoor temperature last night was about -4F. I have converted all my temperatures to F and I most definitly agree the two tables can make things confusing. One last note, the Environment Canada charts show our average temp in jan to be about -19C (-2F). Again, I do appreciate your input and have not entirely discounted the idea that my expectations may be too high.
     
  10. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    There is still much we don't know and your information is changing. The unit that was running 50-75% of the hour is now running 20 of 24 hours and falling behind.
    We don't know what the control set up is or any number of things.
    Were you given an annual op cost breakdown or a bin analysis. Our entire conversation is based on supposition.
    Do you have a buffer tank or is the load side connect directly to radiation?
     
  11. BatocheBob

    BatocheBob Member

    yeah, as time goes on things do seem to be changing a bit. Where the system was running 50 -75% of the time there is now a bit of a change and it is running in excess of 80% of the time. By time I mean the day and not each individual hour. The length of each cycle is changing as well whereas before it might take 2 - 3 hours it is now taking 6 - 7 hrs. to recover a 1 degree drop. My groundloop input temp has remained pretty much the same since the other day, around 40F. The unit I have been mostly monitoring and referring to is the 3 ton H2O to Air unit (Tranquility 27)that heats the house. There is no buffer tank on this unit. The other unit is the Tranquility TMW and it too runs a fair amount of time although I don't think it runs as much as the upstairs unit and there is no time log on that unit. It does have a 100gal. buffer tank. The control board on both units is a CXM board. Speaking of controls the vendor, who insists this amount of runtime (50-75%) is normal has suggested it might be the thermostat and has sent me a less featured thermostat. I am currently using a ClimateMaster NE-32-2000. He says there have been problems and sent me a ClimateMaster ATP32U03. Because of the lack of features I am reluctant to swap thermostats but am thinking maybe it's time. The vendor discussed no operating costs other than to suggest that the T27 would cost less than a hotwater tank to operate. Speaking of hotwater, the T27 does have a desupraheater on it. I read inone of the threads where one vendor suggested this took away from the performance during the winter but the Pros on the forum suggested this was 'bunk'. I'm not sure what you mean by BIN analysis? by the way I think I got mixed up the other night, the 3T unit is the T27 and the TMW is 4 tons. One other thing I will check is my air filter. Although it was just back in October when I cleaned it it might not hurt to check again.
     
  12. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    does the unit run in first stage only, or is it now getting to second stage?
     
  13. BatocheBob

    BatocheBob Member

    That's what kinda' surprised. In spite of running that long I have never seen it go into two stage. Was wondering if that has anything to do with the thermostat and maybe I should change it. trouble is it seems to be a pretty basic 'stat and I don't know if it indicates when 2nd. stage is running. I know it doesn't have the runtime log or the check filter alarm and it doesn't indicate the indoor humidity all of which I kinda' like.
     
  14. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    how do you know if it is running 1st stage or 2nd?
     
  15. BatocheBob

    BatocheBob Member

    My thermostat indicates if I'm in 1st or 2nd stage. Without the thermostat I don't know how you tell.

    As I said in a previous post, the vendor has suggested that the thermostat could be faulty and has sent me a replacement. I have been reluctant to change it out because it does not have all the features my current one has. No runtime log, no filter clean alarm, no 1st/2nd stage indicator and no inside humidity indicator. Another neat feature of my current one isit lights up when you approach it and remains unlit the rest of the time.
     
  16. BatocheBob

    BatocheBob Member

    Well after almost 8 hours i got tired of listening to that unit running continuosly and swapped out the thermostat. When I powered the system back up the temp was a degree above the set point so nothing ran. About 1/2 hour later the house cooled down and the system kicked in. After about 4 minutes it kicked into second stage and after another 8 or 9 minutes it kicked into aux mode for a couple of minutes and then settled back to 1st stage. After a total of 17 minutes I was back up to set point and the system shut down. Looks like I did have a bum thermostat.

    I'll have to talk to the vendor and find out why it kicks into Aux mode. I have the electric element powered off so all that happened is the fan sped up. I'm also curious as to exactly what triggers the second stage. We'll see how it goes for the rest of the night but right now I'm quite pleased. Right now we are enjoying a balmy -16C/3F ;-)
     
  17. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    It is the thermostat the controls the stages. Some tstats offer the user control over this, others don't.
     
  18. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    New thermostat seems to be set for comfort vs economy, you can adjust the staging.
     
  19. zacmobile

    zacmobile Guest

    I'm not sure if it displays 2nd stage but i'm pretty sure the screen turns red when it's in aux heating mode. It definitely displays humidity & has an air filter alarm either a static time reminder or hours of runtime.
     
  20. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    "the system kicked in. After about 4 minutes it kicked into second stage and after another 8 or 9 minutes it kicked into aux mode for a couple of minutes"

    That mode of staging is going to result in much higher operating cost than needed.

    I wonder if the system is producing anywhere near rated output in low or high stage. Someone needs to check.
     

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