Cohousing-L Mailing List: Re: Best Practices: Geothermal HVAC

[Oliveau (Oliveau]

Hey Sharon,
    I think I can answer some of your  questions.
    In-ground geothermal systems has a finite capacity  to produce heat or 
cold (as do air-based heat pump systems).  Cooling is  never a problem with 
in-ground because the ground is about 50-55 degrees in our  area;  but if the 
outside temperature drops into the single digits, the  house can exceed the 
heating capacity of the system, and the electric heating  coils kick in to 
boost the 
system.  This should happen very rarely if the  system is sized correctly.
    This limited capacity also means the the system  cools/heats more slowly 
than a conventional system.  That is, the air  coming out of the ducts is less 
dramatically hot/cold than the air inside  the house.  So it takes awhile to 
get the house to the desired  temperature.  I think this is why you were 
advised to set the thermostat to  the desired temperature and leave it alone.
    But it certainly would make sense to turn down your  system if you were 
going away for days.  And it migh make sense to turn  down your heat at night 
if no one is using your Common Area.  I'll call my  geothermal expert tomorrow 
and find out more.
    Finally, I believe the compressor runs during  cooling as well as 
heating.  My system gives hot water as a side effect of  the compressor running 
(the 
compressor produces waste heat) when the system is  heating or cooling.
 
-Kevin Oliveau
Catoctin Creek Village
 
In a message dated 8/20/2006 8:16:49 AM Eastern Standard Time,  
sharon [at] sharonvillines.com writes:

Is there  anyone out there who understand the best ways to utilize 
geothermal HVAC  units with closed ground loops?

When we moved in our HVAC company said  the most economical way to use 
the units was to set a temperature and  leave it. You could program them 
to go up and down but because of the  length of time it takes to change 
the temperatures, etc. it was better to  keep them within some range. 
Because the air coming out of the vents is  the same temperature as the 
earth (mine seems to measure 65 degrees winter  and summer) the extra 
power used to circulate that air is the only  cost.

Is that true? If that is true, what does the compressor do? Our  units 
have electrical heaters that boost the temps in the winter but I  
thought the summer cooling was just air flow over water coils.

We  have some members who want the CH HVAC set at 82 degrees which means 
with  a temperature swing of 6 degrees, it goes 3 degrees higher or 
lower. This  temperature in an enclosed place with no cross ventilation 
is not  comfortable to inhabit so others don't use the dining room 
without turning  down the thermostat several hours before. Fine for 
planned events but  still discourages spontaneous uses. For meetings we 
turn it down to 74  although I'm not sure the actual temp ever gets that 
low.

This may  be an issue on which we just have to vote on a CH temperature 
but I would  like to find some research to establish a best practices. 
Of course the  whole issue of conservation would be solved by not having 
a CH or not  heating or cooling it but.... Hoping not to go  there.

Sharon
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Sharon Villines
Takoma Village Cohousing,  Washington DC