Moved into a home this fall and had a Geothermal heating system installed. It is a Bosch SM024 Greensource Cdi Model. Pump is Geo Flow UP26-116 - same as what's shown in this thread: https://www.geoexchange.org/forum/threads/new-geo-flo-gpm-circulation-pump-noise.7022/ - same installer?). The loop consists of (2) 150' vertical wells. According to preinstall report, percent of load to be covered by geo is 97.1% and balance point is 16° F. A few days ago the compressor shut off with a message on the unit's lcd display saying "Freeze Condition". Installer came out and check the freeze sensor resistor had been cut which allows it to operate down to 15° F. This resistor had indeed been cut. Next they had the well company come out and purge air from the loop. When they arrived after a couple of hours the unit had shut itself down again. They purged a small amount of air and turned the unit back on. After two days of operation it has now shut itself down again with the same "Freeze Condition" error. I am now very concerned since we have subzero temps on the way this week and the outside air temp is currently only 32° F. During the first visit the technician explained that since this is the first year the system may not perform as efficiently because it hasn't gone through a cooling season and had time to heat up the ground. Additionally he mentioned that the earth around the loops hasn't had time to settle. I've got a few questions: 1) Why would the loop temp be <=15° when the outside air temp is above 30°? Is this normal? Are loops like mine often prone to this type of issue and is there a solution? 2) Is this pump excessive for a 2 ton system? The replies in the other thread would lead me to believe so. Could the water temp issues be related to over pumping? 3) Are the explanations the tech gave me true? Does a Geo system need to go through a cooling season to perform well in the heating season? 4) The bit of loop between the pump and the system is constantly dripping condensate to the point that the floor is always wet and it is now dripping into the wall. Additionally, the inside of the Geo unit constantly has a small puddle of water from condensate on the inside. The inside bottom of the unit is now beginning to look corroded and it's only approx 2 months old. Is this normal? Shouldn't there be some kind of tray or whatnot to collect all the water dripping everywhere? At the moment I'm primarily concerned with figuring out why my unit is constantly shutting itself off and finding a way to correct this. I realize more technical data may be required here and I have some spec sheets I can upload or provide more info if needed.
Hi and welcome! All really good questions. You need to collect some data, the first being what is the actual temperature of the fluid in the loop. If it is really 15 degrees, doubtful. Or is the machine getting, sending, or receiving false info? Eric
Last time a tech came out the unit had been off for a while and when it came back he was reading 34° in / 29° out. Within 10 minutes it was steadily dropping and was down to like 26° in / 21° out. At that point they decided that maybe one of the wells had an air bubble and said that this can cause the water to only circulate through one well. That's when they called the well company and had the air purged. By the time they got here the unit had shut off again. It seems reasonable to guess that it might have reached temps that low but hard to say for sure. Is there somewhere I can buy one of those thermometers they stick into the loop to read the temps? UPDATE: Just read that this can be done with a standard kitchen thermometer so I used one that I have for checking coffee water temp. The incoming water is currently reading 20° F (after having shut itself down, being reset & switched on again approx 4 hours ago) Couldn't get the thing stuck into outgoing but I'm assuming it's 4 - 5° cooler as the compressor is currently running. It hasn't been very cold here yet this year - low's in the 20's a couple nights but mostly between mid 30s and 50s. I just don't understand how it's possible that the temps could be that low.
What did you drill into for the well? Granite? Sandstone? Shale? Clay? Sand/gravel? Wet or dry? It sounds like your wells may have been drilled into completely dry earth given those low entering water temperatures. What type of grout was used to backfill the wells? What size pipe was used in your wells? 150' of well per ton may not be enough if thermal conductivity is poor. Or maybe it is possible you have a kink or crushed area in one of your loops and you are only getting ~1/2 of the expected heat transfer? Is your soil rocky? When they flushed the lines did they measure pressure at the pump discharge? Does the well driller have the pump curve for the flush cart pump? Do you know the diameter and length of the loop pipes and header pipe?
Ground here is considered sandy loam - but there is a swamp a short distance at the back of my yard. I doubt it is very dry all the way down. We are on a well that is only 95' deep and the aquifer we get our well water from is something like 60 or 70' down. The wells were backfilled with Bentonite.
With temps that low this early in the season, something is amiss. A incoming temp of 20 is really low. did you calibrate your kitchen thermometer in a glass of ice water prior to insertion? Verifying the validity of data collected will help us get your solution quicker. Has the flow rate in your system been verified? I know we have a lot of questions... but short of us being " boots on the ground " it will help us help you. Eric
I appreciate the help. The kitchen thermometer is of the analog sort and although it's not calibrated I can tell you that it's within a degree or two based on the ambient room temp and the ice water test. The well folks were back out today and confirmed the incoming temp was around 18 when he got here. The loops are holding pressure and after a few calls they decided something is definitely amiss and to dig down to the manifold to see what's actually happening - theorizing that one of the well loops has a kink in it or something preventing circulation. After digging down they've now discovered that the ground around one of the wells is completely frozen while the other loop is warmish and sloshy sounding - indicating air in the line and the fact that it's warm they are thinking it's not getting any water. So they hooked up an infrared heater to thaw the ground and are coming back tomorrow to dig some more and try to get to the bottom of things. I'll post a follow up here when that happens. In the meantime - any input, thoughts are suggestions about questions to ask would be great.
It sounds like you are on the right track for finding the problem. If it is air in the loop, it may be as simple as the contractor did not use sufficient pumping power to flush the line, did not flush for a long enough time period, or did not verify the loop was fully purged of air before stopping the flush. The following is a flow center installation and loop flushing manual with a discussion of loop flushing equipment and procedure beginning on page 17: http://www.waterfurnace.com/literature/geolink/im1547ew.pdf Common Issues with Geothermal Heat Pumps: http://www.climatemaster.com/downloads/Common_Issues_with_Geothermal_Heat_Pumps.pdf
1) the safeties kick in when the water temp drops down below 20F and the leaving water temp drops down below 15F. So it seems like this was real. 2) Yes. no system should have a 26-116 on it. they are energy hogs and don't add much in terms of pumping power. 3) Yes and no. While it helps to inject heat into the ground, vertical loops swing quick and after a month or so you will not be able to see an effect of summer heat injection, at least not in residential system. 4) Condensate is normal, which is why you need to insulate the components. Chances are that when you are back to "normal operation" with 2 performing loops, the condensate issue might resolve itself.
Thanks Doc. Do you think there is any valid argument I can present to the GC that would convince them to replace the pump or would that be on me? Will the labor and materials cost pay for itself in a reasonable amount of time? And finally, does over pumping present any issue other than energy waste? They were back out today and determined that one of the loops had a manufacturing defect and were not able to push anything through it. They are coming back tomorrow to drill a new well and install a new loop. Seems like a lot of work that one would think could have been avoided and / or caught earlier on but at least it's getting taken care of.
Not sure. Does he assures you a certain performance in the contract? Are the pumps specified? I certainly would bring up the issue why he combines a very efficient geo system with a very inefficient and wasteful pumping solution? It kind of beats the purpose. Legally you are on thin ice, so appealing to his reputation to build you a quality system which is high performing might be a better route. Please being very nice helps too. The GC likely wants quality installs in his houses, and would question the installer.... You do the math, 200 watts pumping difference x 3000 hours per year = 800 KWH per year for the lifetime of the system. Indeed, the lack of flow should have been noticed at the commissioning of the system. You paid for a higher electrical bill for the last months, one more reason to keep you happy with a pump change....
Not sure this helps you but I had a freeze lock out problem that occurred randomly the first 4 years of ownership and then last winter pretty frequently. In checking the water temp it was dropping down to 28 degrees in the middle of the winter. The glycol/water mix shouldve be at 15 degrees for my closed loop - after getting some advice here I picked up a cheap ($10) dilution gauge and found out my mix was set for 25 degrees. After some back and forth I got the driller to come out and increase the dilution. It is now set at 10 degrees which isnt exactly 15 but better than 25. So far in this season I havent had any lock outs. Testing the temp last night the low was 42 degrees on the out. I live in MD which has been decently cold this December. Ill also say that it def took a few years for my pipe to settle down and perform more efficiently with regard to heat/cool dispersion.
Hey goochman - thanks for the insight. Just wanted to follow up and add that a new well was drilled and a new loop installed one week ago. Since then we've had some sub zero temps here and the system has been running for a week now with no problems.
It sounds more like an installation error rather than a manufacturing defect. When they installed the loop they should have filled the loop with water and ran water through it long enough to get the air out (fill with pressurized water on one end of the loop and fill until a steady stream of water comes out the opposite end of the loop). It should have been obvious at this point if the loop was blocked due to a manufacturing defect. The loop was probably kinked or damaged somehow when pushing it down the well.
@arkie6 - I agree. I have no idea what their install procedure is but that makes total sense. Either way, they came out and took care of it at a moment's notice.
