System Performance on very hot days (above 100 degrees)

Discussion in 'General Discussions' started by JRBGEO, Jul 1, 2008.

  1. JRBGEO

    JRBGEO Member Forum Leader

    I am considering installing a WaterFurnace Geothermal system at my house in CT to replace a Hallmark oil furnace. I have been told that on hot days (100 degrees or above) most units will cool the house up to 80 degrees but can't go below that. I have tried contacting WaterFurnace to get some answers on this issue but it is quite difficult to get any replies from them (email or phone calls). Has anyone had any problems along this line? I wonder if this is even a consideration? Again my concern is mostly on the cooling aspect of this system (or any other geo system for that matter) and how it will perform on hot days. The installer I believe will go with a 4-5 Ton unit for a 2500 sq. feet home.
     
  2. Waukman

    Waukman Member

    So who told you that a geo unit will not cool below 80? I ask because the information is not true. A geo unit, properly sized can cool to 70 if so desired.
     
  3. JRBGEO

    JRBGEO Member Forum Leader

    Heard it from my neighbor - and quite frankly I am not sure if it is true - with the investment I am making on a new heating system it better cool the house down to 70 if I want to. I think his comments were based on the experience from a project someone in his family completed for a residential customer in CT. This customer built a 10,000 sq feet home where the HVAC contractor used several geo units for multiple applications (heating the driveway, swimming pool, radiant floors and forced air), multiple wells were needed too. I can see a home this size pushing the envelope to the limit.
     
  4. Waukman

    Waukman Member

    Most likely the situation mentioned may not have been sized correctly based on the need. When you size the system make sure the contractor does the necessary calculations to make sure that the size is correct. A correctly sized system will keep you nice and cool (or warm).
     
  5. JRBGEO

    JRBGEO Member Forum Leader

    Thanks for your input...I'll keep that in mind when I finalize things with my contractor.
     
  6. TechGromit

    TechGromit Member

    My first thought is his system is undersized, my second thought is If he can't keep his house any cooler than 80 degrees when it's 100 out, what does he do when it's zero degrees outside? Doesn't this imply he can't get more than a 20 degree difference between inside and outside temperatures? If the system is heating fine in the winter, than it should easily handle any summer loads.
     
  7. JRBGEO

    JRBGEO Member Forum Leader

    System Performmance on very hot days (above 100 degrees) - need some advice

    I got the contract from the installer in CT that plans on doing my geothermal setup and the contract does state:

    "The new system will have a capacity to maintain 70 F indoors with an outdoor temperature range of between 0 F and 90 F".

    This goes back to my original post a few days ago...does this means that if it is 100 F outside I can only cool the house to 80 F or vice versa if it is -20 below I can only warm it up to 50 F???? I am puzzled by this...the contract price is roughly 25K it seems like a lot of money for these temperature range limitations....

    Any feedback welcome!!!
     
  8. TechGromit

    TechGromit Member

    One of the known problems with Geothermal close loop systems is if there is an extended drought, the ground could dry up to the point where the thermal transfer underground is not as good as it should be. This causes the system not to be able to cool as well as it should. The solution to this problem is to water the ground where the closed loop lines are and within a few days it should run better. If a system is installed correctly, it should have no trouble maintaining a comfortable temperature regaurdless of outside weather conditions.
     
  9. JRBGEO

    JRBGEO Member Forum Leader

    I am hoping the fact that we have an irrigation system in our yard will alleviate this issue.

    Contract states the following as well:

    450' of vertical bore hole will be drilled on the yard with closed loop heat exchanger installed to the bottom using 1.25" polyethylene tubing. A 4" trench will be excavated from the drilling site to the foundation....also the bore holes will be backfilled to the surface with Bentonite grout and the trench backfilled and rough graded. System is filled with GS-4 antifreeze solution and purged of air....
     
  10. JRBGEO

    JRBGEO Member Forum Leader

    The system being proposed for my house is in fact a closed loop system. It seems to me like given the temperature limitations I have described in this thread it would make sense to keep the old system as well as a backup for extreme weather situations - below 0 F or above 100 F - 99% of the time I hope the Geothermal system will be running and on extreme weather conditions I would swap to the 'fossil fuel' system...any thoughts on this idea????
     
  11. TechGromit

    TechGromit Member

    The Close loops problem I mentioned is specifically a Horizonal Close loop problem, Vertical loops shouldn't suffer from this kind of problem. You just need to make sure that the after the piping is installed into the drilled hole, it's properly "backfilled" so there are no spaces between the pipe and the surrounding soil, any spaces or voids will hinder the thermal transfer process underground.

    As far as keeping the old system, I don't think it's nessessary. If a geothermal system is properly sized and installed it should be able to heat and cool as well as any other system available for a lot less $. I guess it wouldn't hurt to keep the old system if it makes you feel more comfortable, other than making for a more complicated duct work install, it doesn't really hurt you to keep it.
     
  12. Guest

    Guest Guest

    Why Not ?

    On horizontal systems why not put a drip watering system just on top of the ground loop pipes? I do have a question ... Why not use Schedule 40 PVC or CPVC? Thanks for the forum!
     

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