I'm getting prices to install a geothermal unit in my house to replace my propane furnace. I figured to get three prices from companies that have been installing geo for sometime. Two are selling Climate Master and the other is selling Water Furnace

The first two only talked about about closed vertical loop systems stating that due to the rock in our area horizontal loop excavation ended up costing more than drilling.

The third contractor came to the house last night. He immediately suggested and open loop. He'd pull the water off of my domestic well and discharge it into a cistern or drain field before flowing into a small spring fed stream on the property. He said we'd have to check to make sure discharging the water would be OK with the local and state regulations.

This sounds like a great idea since it saves the drilling cost but is it a good idea to be using the same well we use for drinking, bathing and washing clothes? His system would replace my existing pump with a constant pressure pump and run to a manifold which would split the water between the house and the furnace. This sounds like a good idea too since it removes the air tank and the pressure switches which will someday need replaced.

As I recall the well is 350' deep and produces 35 gpm. I lived in the suburbs all my life and never had to worry about water. Now days I start sweating every August when everything is drying out and wonder if the well is going to keep producing. Am I worrying about nothing and should I consider this alternate system? Why didn't the other companies suggest this?

I've read that open loops can have problems due to the water. Our water is pretty. Some sediment that is taken care of with string filters, a hardness of 7 grains and no iron or sulfur to speak of.

Thanks.

He may have a good point then.

You'd like to see about 3-5 gpm per ton for the heat pump. So a 4 ton system would need 12-20 gpm. When the heat pump runs, which won't be constant, this amount will need to be flowing. What temp. is the water?

As far as clean water goes, yours sounds way better than what we've seen for open loops in our area. Of the 3 options given you, I'd probably lean towards that open system with your situation. Of course, I'd first recommend an EarthLinked DX system, but if you're going with water source...

Kiphorn,

There is nothing wrong with using the same well for both a geo system and domestic water supply.  From your information it sounds like you have as close to an ideal well as one can get.

 

How old is your well?  If less then 10 years, I sure wouldn’t be change the pump or doing away with the current pressure tank.  The expense to go to a constant pressure pump and the controls to go with it will add a lot to the total installation cost that may not be needed for many years to come.  You mentioned the pressure switch will someday need to be replaced.  They can be had from most home supply stores for under $20.  My point, I see no reason to replace a good working pump system.  I’d get the quote without the well change.

 

Please keep us posted on what you end up doing.  It would also be interesting to know what size system they come up with for your home.  

 

Regards,

An open loop is very attractive if the flow is adequate, if the water is good, and you have a place to discharge the water. Using the same well that supplies your domestic water is not a problem. The only downside is the expense of pumping the water up 350'. But since you have no other loop costs, it is easy to justify the expense. With water in the 50° range you will only need 1.5 - 2 gpm per ton. Plus your COP will be better than a closed loop that can drop below 40°.

Let us know how it goes. I would ask the other two bidders why they didn't offer this system

I gathered some additional information which I thought I'd post so you have more information to consider in the open loop discussion.

I was going by my poor memory about the well since my builder didn't give me a report. That could be because he didn't pay the well driller........ but that's a long story and doesn't add anything to this thread.

On a chance I called the well driller. He remembered my property and my scumbag builder (oh, sorry I said that didn't add anything to the thread). He was kind enough to provide the following information :  The well produces 30 gpm. Its 225' deep. It draws 15 gpm at 120' and another 15 gpm at 180'. The pump is set at 150' and the static level was 55'.

From my water test which was done in February.
pH- 8.12
Copper- Not Detected
Iron- Not Detected
Hardness- Not Detected (the softener must be working)

I called two of the contractors to set up appointments to review their proposals. I'll ask about the open loop when I meet with them. I assume some contractors are afraid of using the domestic well because they don't want that call in August from a customer complaining about not having water.

Thanks for all the input so far.

I'm sure everyone else knows this, why can't you dump the water back into the well?

TopGas,

Good question!  Dumping back into the well is much like having a very short closed loop with a leak.  In very short order the two temps, in and out will merge.  Once this happens the process no longer works.  Most manufacturers want at least 100 to 150 feet between supply and the dump site. 

Regards,

Eric, Makes perfect sense, thanks.

If you Concerned about drying up your well, just have a return well that 60 or so feet deep, 30 or 40 feet away from the main well. That will allow you to replace all the water your using for heating and cooling back into the ground water supply. 

Actually I don't think you even need to bother with the return well. Dumping it right out into the yard will allow it to filter back down into the ground water supply again, it will just take a more water to complete the loop. I have an open loop Geothermal system, and my fear was when the temperature dropped well below freezing, the ground would be too frozen to absorb the water and it would form into a massave lake in the back yard over time. My fears were unfounded, even when it was 20 degrees out I couldnt find any wet ground 3 feet away from the discharge pipe. 

  

The problem with open loop using a typical well pump is that power consumed by the pump approaches or exceeds that of the compressor. Well pumps are both inefficient and operate at pressure way above that needed by a geo heat exchanger.

Result - really expensive system (compared to air source) with same or greater operating costs compared with air source....why bother?

Complete BS! Geothermal Water source open loop system are way more efficent than air source heat pumps. When the temperature gets too cold an air source heat pump no longer operates and you have to rely on the backup heat only, also the air source heat pump has to go into defrost mode to keep the system from freezing into a block of ice. While the water pump and compressor on an open loop system use a lot of electricity , when compared to an air source heat pump, it's at least 2 times more effiecent. Admitly a DX Closed loop system is the most effiecent system, it's also the most expensive to install.   

I found an excellent site that help you figure out how much you will save by switching from one heating system to another.


http://www.energyexperts.org/fuelcalc/default.asp

Thanks for the link.

I fully understand the arguments in favor of geothermal vs air source. I stand by my contention that many pump-and-dump systems do not deliver the efficiency improvement owing to well pump power consumption. Two reasons:

 1)Geo systems need only a few pounds (or feet of head) across the waterside heat exchanger to produce the required flow, but well pumps provide water at much higher pressure. Pumping water at, say, 40 psi and then throttling it across a valve down to 5 psi or so is a substantial waste pf power

2) Typical well pumps are at best approximately 50% efficient, owing to small size and cheap construction. This effectively doubles the throttling loss in #1 above.

We had a thread awhile back concerning a homeowner with an open loop geo and high power bills and we collectively ascertained that the well pump power use was the culprit.

I happen to have an open loop geo system, but it is connected to an artesian well with sufficient natural pressure to drive water through the heat exchanger. I selected a Waterfurnace Envision unit in part owing to its much lower waterside head loss. It is more efficient than a closed loop system since the open loop water temperature is cooler in summer and warmer in winter than attainable by closed loop.

If an application uses pumped open loop water the best solution is a dedicated smaller pump optimized for the flow and pressure needed by the unit. That is probably not feasible in most applications. Other steps to take:

1) Minimize water flow consistent with unit efficiency, freeze protection, and scaling. My unit is allowed to go as low as 1.5 GPM per ton, which is about where I run it so as to minimize water use.

2) Reduce well pump pressure to minimum tolerable

3) Properly size the well pump - no larger than absolutely necessary.

4) Consider a higher quality, more efficient well pump - I suspect that a brand such as Gould, while more expensive than, say, Flo-Tec, will turn out to be quieter, longer-lasting, and more efficient.

Keep in mind that typical resi well pumps aren't designed to deliver the much greater daily load imposed by a geo system. An open loop geo, depending on time of year, could increase daily water use by a factor of 5 or more.