Does that mean we might have been better off with two 3-ton units? Our contract said we were going to get one 3-ton and one 4-ton unit. But at the last minute, the contractor installed two 4-tons (for the same price).  I think he thought he was doing us a favor. Maybe not?

A tighter house will help... there are only so many BTUs stored in the ground, once you have exhausted the BTUs it takes the summers sun to 'recharge' the ground. If you have a tighter house you will require less BTUs to heat your house and thus less BTU's will be required from the ground.

"I'd like to find a way to raise the EWT without having to dig another well (which we couldn't do anyway bc of the price)." Do you have some $$ for some more insulation?

I would really like to think that the geosystem is ok and the problem is with the house losing heat. But isn't 765 feet of looop for an 8-ton system just wrong no matter what? Or is it Ok to "short loop" under some circumstances? If it's OK, I'm fine with it, because obviously it saved a lot of initial money to put in less loop. And bc someone asked, our earth was mostly shale -- it almost liquified in fact when the drilling was done.

I guess insulation is a possibility. We would probably do well to insulate the bottom of our house, because it's not protected from the wind and cold. On the other hand, we could create a moisture problem if we do too much. The attic has a lot of fiberglass batt in it already. Who knows what's in the walls. Do mice offer any insulating benefits? : )

Posted By Princeton N.J. on 07 Feb 2011 07:40 PM
Are you suggesting that perhaps with a "tighter" house, our loop could handle the load? It wouldn't help the EWT, would it?

Maybe and yes it would help EWT.  Lowering the heat load (through insulation and making the house tighter) would help EWT from dropping as low since the geothermal system wouldn't be using as much ground heat with all other things being equal (like outdoor temperature, wind, etc.)

Posted By Princeton N.J. on 07 Feb 2011 07:40 PM
Another thing I've read on this thread is that some people think the problem might be that we only keep our house at 66 degrees (because we don't want to waste energy and also it's just comfortable for us at that temp). Does the interior temp of the home affect the EWT and LWT?

Yes.  Less heat is needed from the ground the lower you keep the indoor thermostat set point (in heating mode.)  Good thing you don't keep the house at 70f or the EWT would be worse.

I would suggest you send out a call to Dana1 (maybe a private message) on this forum for assistance on what to do as far as insulation and tightening the house envelope is concerned.

P.S.  The mice will only help if you get about 300 in bed with you at night.  :-)  Yuk.

Posted By Princeton N.J. on 07 Feb 2011 07:44 PM
Does that mean we might have been better off with two 3-ton units?

For heating, not really other than lower initial cost.    Cooling and dehumidification comfort would be better with the 3 ton units vs. the 4 ton units.

One thing that is hurting you electric cost wise is that single 3/4 HP loop pump that is oversized for your needs.

Insulation and improving the envelope is probably the best way to can handle the situation. As I said, your loop supports a 5-6 ton load, your heat pumps are at 8 tons. Given your loop temp, my gut would be that your manual J heatloss is around 100 kbtu/h. You can battle condensation and moisture with foam insulation, but I am not an insulation expert. It is not detrimental that your loop temps drop down, and yes, it can be designed that way to save you a lot of money upfront. It will cost you some efficiency, probably in the range like 5%, but it will save you thousands upfront. Some around here actually design with a short loop in order to save upfront install costs. No problem to keep your house at 66, higher temps would have made your loop even colder, and increased your heating bill even more.

Posted By arkie6 on 07 Feb 2011 10:22 PM

Posted By Princeton N.J. on 07 Feb 2011 07:44 PM
Does that mean we might have been better off with two 3-ton units?

For heating, not really other than lower initial cost.    Cooling and dehumidification comfort would be better with the 3 ton units vs. the 4 ton units.

One thing that is hurting you electric cost wise is that single 3/4 HP loop pump that is oversized for your needs.

Right now it seems that the (2) x 4 ton units are needed to satisfy the load. Does anyone has any info on the circulation pump, I could not find anything....

.

One thing that is hurting you electric cost wise is that single 3/4 HP loop pump that is oversized for your needs.

Isn't it sorta the opposite?

If that is a 3/4 HP pump, it is working right out at it's max to supply two of these Envision units through 765' of 1-1/4 PE pipe.

What is the minimum normal flow rate for 2 X 4 ton Envision units? 18-20 gpm? Figure out the head and flow and compare it to the pump power.

Then consider what flow rates the Envisions really need to operate with temps down in the low twenties.

You really need a boots on the ground tech.
Your load indicates that equipment may be oversized, loop may be undersized and you are running at temps more common to folks on propane.
j

Posted By ICFHybrid on 08 Feb 2011 02:29 AM
.

One thing that is hurting you electric cost wise is that single 3/4 HP loop pump that is oversized for your needs.

Isn't it sorta the opposite?

If that is a 3/4 HP pump, it is working right out at it's max to supply two of these Envision units through 765' of 1-1/4 PE pipe.

What is the minimum normal flow rate for 2 X 4 ton Envision units? 18-20 gpm? Figure out the head and flow and compare it to the pump power.

Then consider what flow rates the Envisions really need to operate with temps down in the low twenties.

Each 4 ton Waterfurnace Envision 049 unit needs 12 gpm for optimum performance with a minimum  of 9.0 gpm per the Waterfurnace manual.

2 units would therefore need 24 gpm total loop flow for optimum performance under full load.

All pressure drop calcs below are assuming 30% Polypropylene Glycol @ 30 deg F.

Each 049 unit has a pressure drop of ~9 ft hd at 12 gpm and 30F water.  It is assumed that these units are piped in parallel; therefore, the overall pressure drop for the units is less than or equal to the pressure drop for 1 unit (parallel resistance).

Assuming 20' of 1-1/2" hose between the units and the pump results in ~1 ft hd pressure drop for the hoses.

He stated distance of ~115' between the pump and the vertical wells.  This is 230' of 1-1/2" pipe at 24 gpm = ~16 ft hd pressure drop.

He has 765' of bore hole divided between 3 wells.  Assuming everything is balanced, that is 255' of well per circuit or 510' of 1-1/4" PE pipe per circuit.  I'm also assuming these circuits are piped in parallel as is standard practice.   510' of 1-1/4" pipe at 8 gpm (1/3 of total loop flow per vertical circuit) = ~10 ft hd.  With the vertical wells piped in parallel, the overall pressure drop is less than or equal to the pressure drop for 1 circuit (parallel resistance).

Assume 4 ft hd for pressure drop of all fittings.

Total System Pressure Drop is therefore 9 + 1 + 16 + 10 + 4 = 40 ft head (best I could do with the information available).

A Bell & Gosset Series 1535 #353 3/4 HP pump can produce 60 gpm at 40 ft hd per the manufactures published pump curves. This is well over twice the volume needed.  I am assuming this is the pump he has because he initially said it was a Bell & Gossett series 1535 and later said it was a Waterfurnace 3/4 HP pump.  I'm sure he didn't just dream up those numbers.  More than likely what we have here is a Waterfurnace re-branded Bell & Gossett pump.  The Waterfurnace sizing manual even lists a 3/4 HP Bell and Gossett as one of the options.

Looking at the Bell & Gossett series 1535 pump curves, the 1/2 HP pump #352 has ~45 gpm capacity at 40 ft head.  Even the smallest 1/3 HP pump #351 has >24 gpm capacity at 40 ft head.

Looking at it another way, the 1/2 HP #352 pump capacity is >24 gpm with a total head up to 55 ft.

He's wasting ~500 Watts/hr whenever that pump is running and full heating load is needed (running a 3/4 HP motor where a 1/3 HP is sufficient).  He's wasting even more under part load conditions compared to a staged two 1/6 HP pump pack that could have been used.

Posted By arkie6 on 08 Feb 2011 10:34 AM

... running a 3/4 HP motor where a 1/3 HP is sufficient ...

You'd think a ChemE could figger that out ...huh?

Posted By ICFHybrid on 08 Feb 2011 02:29 AM
.

One thing that is hurting you electric cost wise is that single 3/4 HP loop pump that is oversized for your needs.

Isn't it sorta the opposite?

If that is a 3/4 HP pump, it is working right out at it's max to supply two of these Envision units through 765' of 1-1/4 PE pipe.

What is the minimum normal flow rate for 2 X 4 ton Envision units? 18-20 gpm? Figure out the head and flow and compare it to the pump power.

Then consider what flow rates the Envisions really need to operate with temps down in the low twenties.

You need the minimum pump size which provide you with at least 10 gpm per heatpump, preferably having a variable speed pump or at least 2 pumps, one for each circuit. Having 1 pump for all might be inefficient since you waste a lot of pumping power if only one pump is running. Wasting 500W x 2800 hours running per year =$210 annual costs for nothing (at 15 cents/KWH)
However, it does not explain his high monthly bill for running the units, and his low temperature of his loopfield. People here keep saying he is oversized, but obviously his 8 ton capacity is running a lot, and a lot of heat has been extracted from his loopfield. That is an indication that his system is correctly sized for his load, the loopfield might be a bit small but justifiable to save upfront costs, and his house is simply loosing a lot of heat. Manual Js are estimates, which can be off, the actual numbers here tell you that his load is way off. Don't be fixated on a load calculation you have not done yourself, and even then it good to have a healthy skepticism. And a pre-install load estimate does not overrule actual numbers!

I'm talking about the conditions under which this system is currently operating. Viscosities on the coolant go way up in the low twenties. We don't know what is happening there. That affects head quite a bit. And, as far as the head calculations go given your assumptions, I am in agreement with you, but there are a lot of things about this situation that just aren't clear.

Posted By ICFHybrid on 08 Feb 2011 12:43 PM
...but there are a lot of things about this situation that just aren't clear.

Like an undisclosed total lack of geothermal experience.

Like an undisclosed total lack of geothermal experience.

I've read the board FAQs and I'm unaware of any "disclosure requirements". Maybe you could explain it to us.

As the homeowner who posted the original question, I'm happy to disclose the fact that I work as a school administrator and know nothing about geothermal -- beyond what I've learned trying to figure out why my system isn't working as I had hoped it would. And I'm learning a lot from this thread -- people are very generous with their time and experience. It's much appreciated!

why my system isn't working as I had hoped it would.

What is your electrical utility provider there in Princeton?  Is it PSE&G?

I'm happy to disclose the fact that I own two geothermal systems, and have learned a great deal about geothermal by observing and maintaining these systems.  I don't recall any forum members ever being resistant to disclosing their experience, or lack thereof, with geothermal because it may not be a "disclosure requirement", save for one.

ICF Hybrid has no geothermal service, installation, training or ownership experience. Responding to his unproductive questions, answers and comments regarding geothermal is ill-advised.  He leads threads down a non-productive path either for fun or to get his post count up.

ICF Hybrid has no geothermal service, installation, training or ownership experience.

OK. I own five residences, seven if you count small ones. I also own 18 commercial buildings over 20,000 sf each. They all have heating and cooling systems so I might have some experience. I also have advanced university degrees in science and engineering. You can call me "Doc" if you want, but I'd rather you didn't as I haven't been too impressed by people who need you to call them "Doc" or "Gunny" or "Sarge" or "Chief Engineer" or "Skipper" on the Internets. With no offense intended to anyone here who happens to use that a as a screen name, of course. And, I can read a manual. If you think that residential geothermal systems and controls represent some pinnacle of engineering technology, then it just shows how little you actually know.

BTW, I do own a geothermal system and have now installed the field all by my lonesome in the bitchiest weather in recent history. What's next? A one week training course at WTF U?