Ground Loop Heat Pump problems

Iwanttobelieve · February 2009

From what I've seen discussed on geo forums, there does seem to be something of an epidemic of unhappy Geo customers. There seem to be 2 major groups. One is simply poorly designed and/or excecuted systems that are short-looped, both vertical and horizontal.

The other group are systems that actually seem to be performing reasonably close to spec but where the homeowners were totally unprepared for $300 electric bills. A lot of the blame for this has to fall squarely on the dealers that sold these systems for not educating their customers about what to expect for electricity use. I'm burning through $1000-1500 of electricity each heating season, but compared to a $6-8000 oil bill (OK, $3500 at current prices) I'm pretty happy. Unfortunately it seems like a lot of these folks were never told that their electric bills would go up and they're a bit shocked, especially in new homes where they don't have a history of oil or propane use to compare to. The current cold snap has exacerbated the situation since a lot of systems are running flat out and using aux. heat. A lot of the marketing material out there is centered around areas where electricity is cheap and heating seasons are mild where a $150 bill for the whole heating season is not unreasonable.

Wayco Wayne_2 · February 2009

In talking to my friend Mark

from Westminster, MD he sez that because of the extra cold weather for all of January a lot of ground source HP loop are out of capacity and running on back up heat. Yikes! So much for savings on these very expensive installs. What are you guys seeing? WW

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Mark Eatherton · February 2009

Well....

Sounds like a lack of depth, or conductivity or both. Maybe load exceeding capacity?

I've NEVER frozen a loop, but we have 200 to 300 foot deep loops, 10 to 20 foot on center per ton of demand.

Were the field engineered by a qualified IGSHPA designer?

ME

S Ebels_2 · February 2009

Usually

In cases like that some corners have been cut on the loop lengths or the depth of a horizontal tube bed. I haven't seen any problems with vertical bores that are sized correctly.

We have frost like crazy up here in Northern Mich. Towns all over are requesting homeowners to let a constant stream of water flow in their house to avoid freezing the mains and the feed line to the house. From what I have heard, frost depth along some of the roads is now approaching 100".

Hitting that electric resistance backup kinda defeats the purpose doesn't it. OUCH!!

Mark Eatherton · February 2009

90% rule...

THe GSHP subcontractor I USED to use sized the "system" for 90% of the heating demand, and expected the back up elements to come on during dips in to the "Design Condition" zone.

Said it helps keep installed costs down. Goes back to Steve's comments about cutting corners.

Something I've found, is that although you may have 5 tons of equipment (60,000 btuH transfer capability), when you're pulling btu's out of the ground, you MIGHT see 80% of those btu's. If you're pushing (cooling) btu's in to the ground, then you do have 60K worth of transfer ability. It's all right there in their operating manuals, it just does not jump out and bonk you in the head.

ME

Wayco Wayne_2 · February 2009

I've been considering i

installing Geo. Sounds like vertical would be safer. And is there anything wrong with putting a little extra capacity in the loop? WW

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Dave Yates (GrandPAH)_11 · February 2009

in our area

We have one geo dealer who simply targets the A/C load and relies on electric toasters to make up the diff for heating. He's selling a ton (pun intended) of systems. Meanwhile, we're designing for whatever level the homeowner wants to target and building in excess capacity on the geo side for the full range of weather conditions. It's their money & their decision once they're given the full range of options with designs based on an actual heat loss/gain calc. 80% pick-up factor as ME noted.

The half-fast installs will come back to haunt.

Craig R Bergman · February 2009

Depends...

A little extra loop is OK if you don't mind paying for it.
The extra loop might also increase your pumping requirements. It's all a balancing act...

In east central Iowa we design for the heating load and target 92%~98% of the required BTU's to be provided by the Heat Pump. The rest is made up by the auxillary back-up strip heater. We also,almost always, install two stage units because of the lower cooling loads. We want the Heat Pump to do as much heating as possible but we can't allow it to be too big for the cooling loads. It's all a balancing act...

Bergy

Jim_64 · February 2009

hey me

what kind of pump/s are used on those deepies?

Mark Custis · February 2009

Wayne

There is a thread you might look at on the Geothermal Heat Pump Consortium BB. It is about mind melding solar and geo.

I have to agree with Dave Yates, (Nice series on Bean's site Dave, thanks) and ME.

I am buying into Bean's thinking more and more. I got hooked on radiant here and that is almost all we do. We like geo/radiant and solar would mix well.

Steam 'em if ya gotta. Low temp emitters if you don't. More pipe in the floors and the ground makes it work.

troy_8 · February 2009

Geo design

Maybe I'm wrong but I design for 80-90% htg. load from the geo and then use a small mod-con for domestic and to make up the balance of the heat load.We do use desuperheaters. I find if you depend on 100% geo the system is sooo big it pushes the price sky high and payback is neeeeevvvveeeerr achieved. Of course we pay 16cents/kw also. And our cooling loads are minimal. The current project we are installing is half the size of the next quote. When questioned his explanation was it was to keep up with the domestic load. I think all the alternatives should be designed to give the biggest bang and then go back to something sensible, not get too caught up in the "geo all the way" tunnel vision. The customer is also installing a large array of PV. Am I way off or underdesigning? I also used a 2-stage heat pump.

Mark Custis · February 2009

If you go to retscreen

or other solar pay back programs you are thinking correctly. In renewable systems one must not just look at the light at the end of the tunnel, and pray it is not a train.

I agree with your thinking and design on a similar path. Help us if they are cold or short looped.

Toss some solar thermal in the loop with the PV.

Mars_3 · February 2009

Geo is tricky to say the least.

What I have found in sizing these systems is that the cooling capacity will all ways be larger than the heating capacity. That being said you will always need to add some type of supplemental heating if you are sizing to the cooling load of the house. Just my observations of course.

Mark Custis · February 2009

Mars

I got into heat pumps when Jimmy Carter was president. We ran out of natural gas. We sized to cooling in Ohio and added toaster heat to match heating needs.

Now with multiple stage equipment we can go heavy on heat and let the staging adjust to the cooling needs.

How to size ground loops is still whichcraft.

Unknown · February 2009

I don't understand this partial load stuff.

once you have someone on site drilling holes, is drilling one more really that much more money?

Mark Eatherton · February 2009

Grundfos cast iron circs...

220 V. In series.

ME

joel_19 · February 2009

yup

My biggest gripe about geo is all the hype of low bills and fast payback which just aint there or here as the case may be. 18c a kilowatt electric lets think this through. I use 500-600 gallons of oil in a tuff winter. At 3 bucks a gallon that would be 1500 bucks. Ok to convert my house to geo would run around 25 thousand dollars. Now at 18c a kilowatt how long does it take to save 25 thousand dollars....... Right I should give the 25k to Madoff instead.

Lets say it cut the bill in half (which it won't) but lets just go with that your talking 30 YEARS or more for payback.
or am i missing something

joel_19 · February 2009

yup

My biggest gripe about geo is all the hype of low bills and fast payback which just aint there or here as the case may be. 18c a kilowatt electric lets think this through. I use 500-600 gallons of oil in a tuff winter. At 3 bucks a gallon that would be 1500 bucks. Ok to convert my house to geo would run around 25 thousand dollars. Now at 18c a kilowatt how long does it take to save 25 thousand dollars....... Right I should give the 25k to Madoff instead.

Lets say it cut the bill in half (which it won't) but lets just go with that your talking 30 YEARS or more for payback.
or am i missing something

Mark Eatherton · February 2009

The math

550 gallons times 139,000 btu/gallon = 76,450,000

76,450,000 X .80 (assumes 80 % system efficiency) = 61,160,000

61,160,000 /3413 = 17,914 KwH

17,914 * $.06 (assumes a COP of 3:1) = $1,075.00 per year.

If it WOULD have cost you $1,500.00 for oil, with geo you would have saved $425.00 per year.

Hence, $25,000 divided by annual savings of $425.00 per year, results in a simple cash on cash break even of 58.8 years.

The compressor has a life expectancy of around 20 years.

The electrical plant generating the electricity has an efficiency of maybe 40% on a good day.

The ONLY reason I can see that it makes sense to do it is because the "source" is free. Obviously, noting else is...

Top that with early compressor failure rate of over 50%, and it tells me that maybe it's a technology who's time hasn't come yet...

ME

Mars_3 · February 2009

What I am Hearing

is that my geo guys from PK Geothermal in colorado is that the manufactures are trying to get compresers that will adapt to load AKA modulate. I do not know that they are there yet but that is the hope. With the ability for the compresors to adapt to loads obvisly there will be substantial savings hopefully. The manufacture that I know of that is looking into this is Econar out of Minn. Ive had good luck with there product line as has my Geo guys. ME. BTW I was in a house today and saw the oldest steam boiler I have ever seen, f ing amazing house was built in the 1880's and the boiler looked original. I hope to do a boiler replacement and if you have the time I think you would enjoy the old system. Oh ya no hartford loop on the original sysytem wow.Good stuff and hope to hear from you soon

BC_10 · February 2009

Obviously payback varies enormously depending on the situation. Last winter when oil prices spiked I was looking at a less than 4 year payback. Even now it's well under 10. Electric/fuel prices, install cost, loads, etc all vary way too much to say that it does or does not make sense for everyone.

I fully agree re the "green" aspect of geo being wildly oversold. If you're in a region that has a lot of coal in the power mix you neet a COP of something like 6 or better to beat a gas mod/con on CO2, NOx, SOx, etc. Of course if you're all hydro or nuclear, you're good to go...

BC_10 · February 2009

In terms of the drilling, I think the cost does tend to be pretty linear with footage until you get into really huge projects, at least from the few quotes I've looked at. However, the incremental cost of the whole system shouldn't increase proportionally to load. I don't believe a 6-ton compressor costs twice as much as a 3-ton. At least there's no way it costs twice as much to manufacture, what they sell it for is another matter!

I believe a major reason more systems aren't sized to cover the whole load is that there is this mantra out there that you only size to the AC load or you will have poorly performing AC in the summer. Obviously there are ways to deal with that by using multi-stage heat pumps, multiple units, hydro-air, etc, but old habits die hard. It comes back to what I said below - the industry as a whole tends to be very central-US centric where AC is of much greater signicance than heating. When I was designing my system I found that in general the Canadian companies' literature made much more sense since they are used to a heating-dominated climate.

BC_10 · February 2009

One other thought - when I was designing my system I was seriously considering going with an "undersized" unit to handle the load down to about 20F (0deg design temp). It looked good at first because it would still pick up over 90% of the load over a season (or something like that, I don't have the #s in front of me). However, when I went to size the loop, the required length for the small system was barely shorter than the one for the larger system. This was because the limiting factor was the annual load on the loop, not the short term loads. Even though the system was 2 tons smaller, I still needed 90% of the loop because it was handling 90% of the load. I suspect this is more of an issue with heating-dominated areas - I was assuming no energy put back into the ground from AC.

Jim_64 · February 2009

in series

which act like a standard, compound well pump?

joel_19 · February 2009

under 10?

What do you pay for juice?

BC_10 · February 2009

Full disclosure

I should have said that there's no labor cost in that figure (except for the excavator). I don't have the exact figures here, but in very rough terms I'm using about 10,000kWh per year at $.10 to $.12 per kWh. That's compared to about 1400gal of fuel oil per year (and that's down from 2000 gallons due to added insulation etc.) So, my annual savings has been between $2500 and $4500 depending on oil prices. Even if I did figure in my labor, I'll easily be under a 10 year payback unless electricity spikes and oil crashes dramatically.

Depending on how you want to manipulate the numbers I could also subtract the cost of replacing my old boiler from the geo system. That would have been $8500 including chimney liner, new oil tank, etc. So while it's not particularly relevant for most people, in terms of actual cash outlay vs savings for me the system will have paid for itself by the end of this season, less than 2 years.

klaus · February 2009

Electric rates

My 2-1/2 year old house, all GSHP system. No back-up resistance. My rates have averaged 10-1/2 cents/Kw. Average bill $137/ month. That's for all my electric, not just heating and cooling. I have the spread sheet if you'd like to see it.

Back to your original question Wayne, there's no reason you couldn't install an extra loop in your system to increase efficiency. I think it would be a great way to go. BUT It's generally not done because it raises the cost of the project and most every job out there is a competitive bid. We try to sell the customer on the value but we all know $$$$.

ME, I sincerely respect your knowledge in this industry but if you're loosing 50% of the compressors in the GSHP's your installing there's something wrong. Over the last 7 years we've done over 1000 tons of GSHP's for our local schools and have yet to loose one compressor. There's been a few boards and a reversing valve or two, but that's it so far.

GSHP's have proven themselves to be a very reliable, cost efficient way to heat and cool homes and buildings in our area (Eastern Iowa, low temp in the last three weeks, under -30 degrees F).

Mark Eatherton · February 2009

Yup...

as per usual. One pulling, one pushing, and NO point of no pressure change...

Defies explanation as to how it works.

ME

Mark Eatherton · February 2009

I hear you...

And trust me, we've asked them to tell us what it is we're doing wrong so we can correct it. They tell us we're working them too hard (winding failures, all) because we're using it to do year round DHW preheat. Claim were running them too hot (120 F) as well.

My thoughts are this. If it is so sensitive, why isn't it in the installation manual, and if they are so sensitive to high operating temperatures (and pressures) why don't they have their own internal high limits to keep me from working them too hard or too hot.

Of the 14 installations we have out there, 8 have failed, and one is on its third compressor. We're not doing thousands of tons like yourself, and probably won't until someone comes out with more reliable equipment and or variable speed equipment.

I'd love to be able to say it works great, but based on field experience, this industry has a long way to go...

ME

Rich L. · February 2009

Variable speed

I'm anxiously awaiting a variable speed "load matching" compressor for heat pumps. I've been using Fujitsu units for most of our mini-split ductless installations lately and I love their units. They (mini-splits) have the capability, why don't GHSP's yet?

This also sends the SEER, EER and, HSPF ratings through the roof.

I believe that it's Climate Master that has a unit out now that's supposed to reliabily hit the 140's for water temps. I saw one early last year at a trade show (Iowa Heat Pump Association's Annual Conference) but haven't heard much about it lately. Big draw back - It's heating only. Then we'd have to add a seperate cooling system too, I don't think so.

Unknown · February 2009

we saw a few things like what you saw mark: I call 110 the max for geo now, and when we do DHW preheat that is the max as well. Generally with radiant I'm trying to get max temps to 105 or even 100, perhaps with supplemental.

So far, so good...

GMcD · February 2009

Cast iron in geo system?

Any problems with corrosion on the ferrous pumps? Usually I spec all bronze, as the HDPE piping is not an oxygen barrier material and can introduce oxygen into the system...

A.J. · February 2009

Disconcerting

I am always worried a little when we try something new and the geo-radiant system we are about to start soon is no different. The frustration in your post Mark really jumped out at me and is making me wonder about my choice of getting into the geothermal market. If a guy with all your talent and experience is seeing problems when how is an average guy like me going to pull it off. If I may ask are you still going to install geo systems at there current level of efficiency ?

Mark Eatherton · February 2009

A.J.

I talk to a lot of people who are in the GSHP business, and they all recommend running the system supply temperatures on an outdoor reset schedule, and keep the maximum temperatures to a high of around 110 degrees F. The technology is going to take a while to change. I've spoken to Mitsubishi about the possibility of using their variable speed compressors on a typical hydronic job, and am told that it MAY be a possibility in the future, bit probably not within the next 5 years.

On the other hand, in speaking with some other North American manufacturers, using Mitsubishi compressors, they say less than 5 years.

So for the time being, we are pulling our collective hydronic horns back and sticking with proven reliable technology, like modcons and solar thermal. If someone twists our arm, we will do GSHP, but will require a substantial auxiliiary back up to insure comfort and reliability.

ME

[Deleted User] · February 2009

The general consensu of the geo loop filed installers I've met

is that due to the fact that the loop field runs relatively cool, the chances of oxygen diffusion is so low as to not worry about it... Yeah right. I've had the opportunity to look in to some loop field pumps, and saw more corrosion than I would have like to have seen, but they (GSHP Industry) do not seem to be too worried about it.

Remember, these are the same people who are of the opinion that PE doesn't expand and contract much (same coefficients of expansion as PEX) and that there really is no need for an expansion tank on these closed loop systems, nor a need for air removal.

Unfortunately, this industry is relatively unlicensed, and is suffering the same problems the solar industry went through in the 80's. In fact, I wouldn't be suprised if a lot of the former vacuum cleaner sales men turned solar expert over night are now plying thier skills in the GSHP biz... This is not to say that there are not some well qualified folks working in that field, but there are some real gems out there short looping and undersizing systems just for the sake of a sale.

ME

John Vastyan · February 2009

geo challenges?

Whew, one writer spoke about frost depth of 100". Those're tough conditions for any system. Who's designing for that?

We've now got a 36,000 BTU ClimateMaster THW (what I like to call a "geothermal boiler") that's capable of cranking out 145 degrees . . . right out'a th' ground w/no electric toasting. Dave Yates is the installer; he and his guys've done a terrific job making all the connections to a 1,200 s.f. staple-up radiant system with domestic, too, and an injection loop that ships heat 50" underground to a garage with 600 s.f. of staple-up and 250 s.f. in-slab. System works like a charmer. In fact, we've measured n' re-measured the heat output of that thing, amazed at its ability to provide 156 degrees - 11 degrees beyond its rating. I told the folks at ClimateMaster about this and they're nicely surprised, too (incoming ground loop temps are 47-48 degrees).

The key, I think, was to go 10-15% deeper on the bore-holes.
I figured that we'd have only one shot at making this right, and I wanted more than anything to avoid problems. Hey, the drilling rig is there, right? Just have 'em sink it a bit further.

Tell the customer this story . . . having a wee bit of extra geo-exchange capacity was all it took in our case.

Rich L. · February 2009

Climate Master

Hi John, As I understand it now the Climate Master THW is avaible in one size only (@ 60hz) and does heating only. I use mine for both heating and cooling. I believe many are set-up this way and that makes this model impractical for most, IMHO.

But I do like those temps...

Bob Bona_4 · February 2009

I'm with you

Mark, I did a DX geo last fall. Umm, I think I'll take a pass.

22 based, which kind of defeats the whole "environmental" thing. Linesets have to be larger than typical tonnage, because the enguneer said "we are pushing these compressors to the edge". Upon start up, I was hearing great things about how the compressors like to go off on high head if demand conditions aren't just so.

Support, down to manuals/tech literature, was practically non existent, and information was highly guarded by an over paranoid engineer. I even had to sign a non-disclosure/privacy note before the equipment was delivered.

Standardnization? Right. The secrets on the systems idiosyncrancies (sp?) go to the grave.

Geo has a LONG way to go before I can heartily endorse it.

Unknown · February 2009

cooling

My Climate Master rep told me the THW was designed by a Viessmann engineer and I do see many similarities to the Vitocal units. (like the piping connections on the top, nice!) In europe from what I understand most ground source heat pumps are heating only and cooling is achieved by going right off the ground loop to radiant or fan coils, the Viessmann heat pumps actually have a feature on their control for this. Much higher cooling efficiencies are achieved, something like a COP of 20 from what i've heard! We just got one to replace our old Genesis in the shop, I can't wait to get it going!

Rich L. · February 2009

Re: Cooling

If I understand yopu correctly your suggesting using the ground loop water to run through a coil in the air handler for cooling? We have right around 54 degree water year round(Iowa). I can't see this temp water providing adequate cooling AND dehumidification. As the cooling season wears on and the ground loop slowly warms performance would continue to drop off, right? What am I missing here? Thanks, Rich L

Mark Eatherton · February 2009

What, in your opinion, drive the bus of human comfort...

Air temperature or relative humidity?

Consider the use of a small dehumidification plant, either desicant or refrigerant.

Check out Healthy Heating's web site for a real cool comfort calculator. You might be surprised about the base loading capabilities of a direct exchange system, and also the dynamics of the aquifer into which you are tapped.

Ground Loop Heat Pump problems

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