Geo-thermal HVAC and wells question...

[davesl708]

70 degree ground water shouldnt effect the ability to cool the house. Its better than an air-to-air unit that is trying to do the heat exchange with 90 degree + outside air.

We can take 40 degree ground water and keep a house heated to 70 in the winter. Using 70 degree air to keep it cooled to 70 should be no problem. Geo's work in florida, and I am sure their ground water gets hotter than in KS

Agreed but several co-workers had problems in the 100+ deg. days we have here using horizontal loops. My wells have no problem keeping up.

 

[techman]

Ground temp rise to the levels mentioned seem to be a bit exaggerated

Paul

 

[LD1]

Agreed but several co-workers had problems in the 100+ deg. days we have here using horizontal loops. My wells have no problem keeping up.

I think they must have a system sized too small, say for 90 degree ambient then?

Back with the single stage HP's, most HVAC "pro's" wanted to size on cooling load to get dehhumidification. End result....on hot days, it runs ALOT just to keep up. And was (in my area) grossly too small for heating, and anything under 30-35 degrees requires a secondary heat source.

Temperature is irrelevant. ITs temp change that matters (delta T). If the target for the house is 70 degrees year round, cooling it from 100 degrees outside is no different than hearing it from 40 degrees. (both 30 degree delta T) Both require the same BTU's.

In my area, its not uncommon to have 95 degree summer days. And not uncommon to hit single digits or below in winter. Thus the heating load is 2x to 3x more than cooling. If I were getting a single stage, I'd still size based on heating load. Wont get as much dehumidification in the summer. But around ehre, heating is the primary concern with AC being a nice side benefit

 

[TheGoose]

First off, do you use the well for your household needs? If yes, the well will need to be properly set-up to make sure it can handle the household needs as well as the HVAC. The pump size needs to be carefully determined and either a CSV or Variable speed control used in conjunction (I prefer the CSV).

I have dealt with a few pump and dumps. I have seen several return wells lose their ability to take all the return water, resulting in a very wet and messy yard. There are several reasons this happens but I suspect the minerals in the water come out of solution when the pressure drops.

Also, if you go open loop make sure you get the hvac unit with cupernickel coils. And check the hardness and pH of the water. Too hard or low pH and you'll spend more money on maintenance than you save on energy.

Personally, I think that it would be better for you to put in a closed loop. it will cost more money but I think at the end it will reduce the headaches of dealing with an open loop tied in with your domestic water system.

 

[techman]

Just a trivia point. many people have commented over time about the insulating effect of plastic geo pipe. HDPE had an average thermal conductivity of 0.46 W*/M/Deg C. Using HDPE information for the pipe, and assuming a 3/16" wall, the thermal conductivity of the pipe is 0.0012 deg F/BTU.

If you take a 4 ton geo unit, that is 48,000 BTUs. Now assume 2,000' of pipe (my system is 4 runs of 500'). That will then be 24 BTU/foot. So the temperature drop/increase through the plastic will be 0.03 deg F over a foot of pipe with the given conditions.

From this one can see that the temperature loss/gain due to the plastic is indeed very small.

Paul