HI -  just found this forum.  Even though it's 20 degrees outside right now, I'm thinking about cooling next summer.  Currently have a standard Gas forced air furnace.  With Electric powered Central air.  Recently we attached to city water and have a spare well that is not being used.  The well has great flow.  Was thinking about adding a water to heat exchanger in my forced air system, replacing the pump in the well with one that is sized right and can handle the duty cycle.  (like a low pressure, high volume.). No pressure tank, just run the pump when the thermostat calls for AC.   Use the  discharge water to irrigate my large garden.

I'll need to pull the well to find out how deep the current pump is.  We have 2 wells on the property and I don't think a permit was pulled for the one I want to use,  can't find it.

Any recommendations on how to do this or where to look for information on how to do this properly?

Thanks

Barry

Are you wanting to use a heat pump on the water or just circulate the water through a coil in the plenum? If you just use the water you'll probably have difficulty getting adequate cooling and dehumidification.

If it was me I'd be looking at using the well to feed a split geo unit to replace your A/C. It would provide most of your heating and all of your cooling. On the coldest days the gas furnace would kick in to finish the job.

I was wondering if just pumping water through a coil in the plenum would work?  We are on a heavily wooded lot, so AC isn't used a lot in the summer.  Just a few handfuls of hot days.  The AC unit is old.

Cost is an issue.  How much is a split geo unit?  I've also heard heat pumps aren't real efficient for heating and I really don't want to deal with the discharge water in the winter.

How do closed loop verticals work?  Could I just pull the pump on the 5" casing I have and drop a loop down it?  The well isn't being used for anything right now.

The furnace is fairly new and I have access to a lot of wood.  Probably go to an outdoor woodburner if I want to replace the heating solution with something cheaper.

Thanks

A geo is going to cost, how much depends on the details. If you have a good well with plenty of volume and a place to dump the water then I can't imagine going to a closed loop geo. That would cost more.

If your cooling need is very light then I suppose pumping straight well water through coils might give you enough cooling depending on your load and expectations but I'm skeptical. You'd have to run some calculations to see what you can expect.

You may be able to pump from one well and dump into the other. If this is not feasible, you can dump back into the same well.

If you are supplying water at 50 or higher to the coil, dehumidification is likely to be weak or non-existent. It might still work OK in an application where AC is rarely needed or where humidity is less of an issue, such as areas west of I-29

jonr.....I have never heard of taking water out of the well and being able to dump back into the same well. How is that done?

Generally the well cap will have the drillers name under the cover and sometimes even the total depth, casing depth, pump info etc.  However, once you have the drillers name, you can usually contact them and ask for the drilling log (many keep the logs for 5-10 years as local regs often require and other keep the logs indefinitely).

You are going to want to know the sustained well yield/specific capacity, pump model, pump intake depth, etc.  The majority of michigan is underlain by glacial deposits that exhibit a shallow water table and reasonable high well yields which work well for open loop installations.

-Adam

jonr is talking about a "Standing Column Well" or SCW. A good overview is provided at http://www.hvac.okstate.edu/research/Documents/Orio_Johnson_Rees_Chiasson_Deng_Spitler_05.pdf

They are usually installed in heating dominated areas with shallow bedrock where resultant low permeability requires deep boreholes to yield much water. You need 50-75' of water column per ton of heating/cooling.

-Adam

True, an existing well that was not intended for a SCW may well not have enough water column to provide the performance you need.

The use of more bleed would help - you can vary all the way from 0% bleed (pure SCW) to 100% bleed (pure open loop) as needed.

Since you are concerned only with cooling in the summer, perhaps you could just use the bleed/dump water for the lawn?

Adam - The well is probably dated around mid 1960's. I have a well driller's name that was on a sticker on the electrical subpanel for the well, but he's passed away. Don't know if he was the original driller or did some maintenance and left his sticker.

If I thought this was doable. I planned to pull the pump and replace it with a pump sized appropriately. Not use a pressure tank and pump directly through the open loop. At the tap I'd get 5 GPM, but the well only ran for very short periods filling the pressure tank, then going idle until needed again. I let the hose run outside over night before and the well never ran low on volume.

I'm pretty confident I can do this. We had 2 wells on the property and I abandoned the other one by pulling the pump using my tractor's front end loader and some pipe clamps. That well pump was 140' deep and pump was down 100' I think. That well was on the other end of the property and had volume issues, but the water quality was great.

It sounds like the opinion so far is not very good results happen from just trying to blow air through water cooled coils in the plenum. So I'm probably going to abandon the idea.

IMO, if you had a conventional system for dehumidification and an oversized water-to-air heat exchanger, direct use of the ground water for cooling could work.  How much dehumidification depends on how tight the building is.

I do not share Jonr's confidence in a happy combination of a well water to air coil in tandem with a "conventional system" if that system is a central heat pump or AC. My concern is that the water coil would strip the house of some sensible load, leaving a proportionally much higher latent load. That results in the conventional AC becoming oversized for the remaining load, and it will not operate at the required very low sensible heat ratio.

One option would be to combine the well water air coil with a central dehumidifier. Dehus remove latent load but add to both the sensible and overall load, which the well water aircoil might meet.

I doubt such an arrangement would be particularly cheap, efficient, or easy to control.

Yes, I did intend to include both conventional A/C, extra cold conventional A/C and dedicated dehumidifiers as options. Tight buildings have a high sensible to latent ratio - in theory, a perfectly tight building would need no dehumidification at all (after an initial drying).

Do not neglect internal latent loads - respiration, perspiration, bathing, cooking, houseplants, standing water in the loo, dishwashing, handwashing, etc.

Thanks for the info about the well....!