I went to a home show this weekend. Out of 5 geo contractors there, four said without question that they preferred closed loop over open loop. One said it didn't matter. The others gave the following reasons for closed loop: higher pump wattage with open loop, equipment life, and water waste. Their primary concern seemed to be equipment life.

One said that pumping all that "new" water would tear up the equipment. One said that they had to replace one whole unit after 1 year on an open loop because of the water quality. The others just expressed concern about scaling in the exchanger and pump life.  But they all said they do open loop sometimes and one commented that they just replaced an open loop unit that had been in service for 20 years.

I asked about what to test well water for to determine if it was suitable for an open loop system and they all had that deer-in-the-headlights look. One said "they" (meaning the water well drillers) have a standard set of tests. I said "you mean for potable water?". He nodded. I said "well what tests are important for a geo unit?- I doubt it cares about nitrates." He agreed about nitrates not being important but couldn't really say what was. Another mentioned the biggest concern would be iron bacteria as that is worse than hardness on the heat exchanger. Another mentioned sediment as the big issue.

I was surprised that there was no standard panel of tests and recommended limits. Or maybe there is and they weren't aware of it.

I have an unused well on my place that was replaced for domestic use due to nitrates before I bought the place. I'd like to at least consider using it if it has acceptable water quality and quantity rather than closed loop. Since the well is there already it could potentially save me money and maybe even give me a higher COP than a closed loop. But if the water quality will set me up for high repair costs and shorter life then I'd bite the bullet for the closed loop cost.

So (other than water volume output) what should I have the water tested for and what results should give me comfort or concern?

The ClimateMaster Installation Manual covers the issue in a somewhat oversimplified manner. But I doubt that very many people actually calculate the Ryznar and Langelier indexes.

Greg, I attended the Wichita, KS, home show and the preference was for open loop with 4 of 6 installers I talked to. Mainly due to higher COP and lower install cost. But when pressed about water quality in the area they kinda hemmed and hawed. I believe a standard water test should get you useful info to evaluate compatibility with the equipment as it test for iron, hardness, ph, etc. But as to acceptable limits for use in GSHP equipment...good question. Several vendors did state a big problem is heat exchanger problems as they are constructed of thin metal.

Someone I know with a 5-ton Climatemaster pump and dump system has had to replace the Taco flow controller 3 times since 2004 due to hard water and mineral buildup. So about every two years. I replaced it the second time in 2008 for the homeowner. Part cost about $120 from local HVAC supply house. Then a month ago the installer replaced it again for over $600 and the same part cost over $350!! Do they markup the the part a bit? Hmmm..Sorry about the venting.

For our upcoming home, it will be a closed system. Dave

Is there anywhere I can get the Climatemaster Installation Manual? It looks like I need to be a contractor to get in that part of their website.

I don't mind getting into a setup that would require routine filter changes and say an annual treatment to descale but I want to avoid a situation like Farmboy describes where equipment has to be repaired/replaced frequently. That would wipe out any upfront savings quickly. I understand why the repairs are costly - the contractors have a lot of expenses and they need to make a living at the end of the day. I just don't want to be the one who's providing them a regular income LOL. And I think most contractors would rather make their money installing good systems that rarely need repair (happy customers) rather than making it off systems that need repair frequently (grumpy customers).

I think you can actually download the manual from the ClimateMaster website.

Table 1 on Page 12 at http://www.climatemaster.com/downloads/69197337.pdf
However, a much better understanding of water quality and heat pump scaling can be found at http://geoheat.oit.edu/otl/scaleghp.pdf.  Specifically, the state maps will give you some idea of hardness but not of iron bacteria fouling potential.

Either way, several of the parameters have to be measured in the field.

-Adam
Hydrogeologist

You guys are right as usual. Those installation downloads were hidden under the Commercial side of their site and I was looking residential.

Adam, that is a great link and does put a lot together for me. It looks like Ammonia, H2S, O2 would all have to be measured in the field to get accurate readings. Are those the ones you were referring to? Would these tests be something a well driller would typically be able to perform or who would I contact?

Good reference, thanks.  Supports the idea that it is hard to get scaling at the low temperatures involved with GSHP heating only.

pH, alkalanity are others that are best field-measured.  I don't know of any drillers will have the capabilities but most geologists/hydrogeologists would be able to do it.

Hardness and iron bacteria are the most important for initial screening.

Adam:



That was a great link.Thanks! I now understand looking at the ground water maps there why in MA there seem to be some many open loop installations. I got my system in 2007 and from what I hear from my installer's techs they are doing more closed loop these days than before.



Sam

gregj : "Since the well is there already it could potentially save me money and maybe even give me a higher COP than a closed loop." Also, if you compare heating capacities, for example in case of Tranquility 038, open loop with EWT 50˚ has a 27% to 30% advantage (depending on flow) over closed loop with EWT 30˚, about 6000 Btuh. This may allow you to install a smaller unit. Saving you in upfront heat pump cost, ductwork cost, operation cost, and perhaps resulting in better summer dehumidification. Performance data for different EWT 's are available for download from Climatemaster.

Regards,

Masoud

P.S., I'm happy with my closed loop!

Posted By gregj on 15 Feb 2010 09:54 PM
I went to a home show this weekend. Out of 5 geo contractors there, four said without question that they preferred closed loop over open loop. One said it didn't matter. The others gave the following reasons for closed loop: higher pump wattage with open loop, equipment life, and water waste. Their primary concern seemed to be equipment life.

Most of the country, water is unsuitable for open loop systems. This is probably why the bulk of the installers lean towards closed loop systems.  Different areas of the country may have clusters were open loops are dominate, but for the most part, open loops are the minority. (Pretty much all of the South Jersey Pine Barrens aquifer is suitable for open loops, with a few exceptions)  I haven't a clue what they are referring to "Water Waste", with a return well, the water is recycled just as in a close loop system.  As for "higher pump wattage", the higher COP more than makes up for the more wattage.

If the well water turns out to be less than desirable quality it looks like a stainless steel flat plate heat exchanger wouldn't be all that expensive to use to isolate the heat pump from the well water. I'm sure that would affect the ewt and therefore COP but have no idea how much. Would the need for an isolating hx put it similar to a closed loop in performance?

Four out of five car salesmen recommend a more expensive model :-).

That's unfair. If open loop is viable, knowledgeable contractors will present it, knowing that its reduced cost might make a sale where closed loop might be prohibitively expensive.

I think all of the contractors I talked to were subbing out the loops so maybe they were getting a little markup but I doubt it was enough to be the motivation.

My impression from the discussions was that they knew with closed loops they were going to have a near 100% chance of success at the starting gate with minimal chance of problems down the road. With open loop they were uneasy about the problems down the road. And I'm definitely with them on that thinking.

But I also want to take care of my dollars so before I give up on the lower upfront costs and potential for a little higher COP for open loops I want to evaluate my particular case and see what the risks really are.

Quick note here.... if you have an existing well and if your water checks out good or even just borderline for volume and/or quality... you could try the open loop knowing that your not out much if something didn't pan out and the open loop didn't work for you. You could then in stall the closed loop heat exchanger and pipe it in. Thinking about this possibility when you plumb the unit for open loop system can make a future conversion painless and cheap. Thie potential for upfront savings was too much to ignore. WHen we built our home we had to have a well anyway, so we planned around a open loop system, and then I put supply and return lines under the floor before my basement was poured, from mech room out to the back of the house in case I have to convert someday to a closed loop system due to something unforseen...performance issues, water issues, or maybe even code issues.... There's no guarantees as water levels and quality can change too, but so far no complaints with the open loop system (2.5 years now and we were actually over the concentration levels recommended for a few of the minerals, annual cleaning has been all that it wants)... and I love the rock steady entering source water temperature.

I'm not sure how cheap it would be. In addition to installation costs to switch, keep in mind the tax credits that are available now (I doubt the 30% credit would apply to a future switch), and also financing options that may be available to you now that may not be available in the future (including low current interest rates). Some of this may apply to you, and some of this may not.

Jokin,
I don't know where you are located but I was curious as to what water temps you are getting (EWT and LWT) or the Delta T. How many tons? Flow rate? I also have a pump and dump system here in SW lower MI where the underground water temp is a relatively constant 55F. I am also very pleased with my system performance.

I did much the same thing as Joykin - unit sized for closed loop, xtra conduit beneath slab for xtra closed loop line, but running open loop for now