Bad geothermal install followup - need more loop?
I posted about our problems in a previous thread.. To not have to re-hash, I had a geothermal install done with a 3 ton ClimateMaster Tranquility 30 (replacing a 3 ton HVAC electric cool/gas heat) that went very bad. The installer refused to finish the job and fix whatever was causing runaway energy bills. We contacted two other contractors who both agreed that the zoning system was improperly installed and that there was probably not enough loop (I estimate that there was maybe 600 feet of loop installed using horizontal boring).
One of the contractors came out and bypassed the zoning system completely. They flushed air from the lines and pressurized them - finding and fixing 4 leaks that were all loose connections inside our basement where the install happened. They also replaced the thermostat with one from ClimateMaster that gives us information on the status of the unit (entering and exiting water temps, for example). From that point, the system has been at least steadily heating the house. We've been seeing exiting water temps of 40 and entering temps of 46 - almost always 6 to 7 degrees difference - and leaving air temp always 95 or above.
We went away for Thanksgiving and I had the system set to 60. When we got back, I set the system to 71 and it's been heating for the last 2 hours at least. The thermostat now shows 27.1 leaving water temp and 31.9 entering water temp - a difference of less than 5 degrees - and a leaving air temp of just 88.7. The pipes leaving and entering the unit are covered with a layer of frost/ice now.
My question is this: is this a sign of an inadequate loop size?
You should never set back your system temperature so far. I tell customers a 4 degree split at most. So even when gone for a while the heat pump is not trying to extract such large amounts of energy from the ground all at once. I would turn on your electric heat, get the house up to temperature and then see how the loop is doing.
When you say 600' of loop do you mean 600' of boring with 1,200' of pipe or 300' of boring with 600' of pipe?
Typically for our three ton horizontal boring systems we use a minimum of 800' of boring with 1,600' of pipe and up depending on lad and ground conditions.
I would also get a qualified contractor to get the zoning system up and running, once zones become satisfied the load on the system will be reduced and more capacity available for callers.
I didn't write the book I just read it!
Hmm. Ok, I'll run the emergency heat for a day or so to give the ground a break and defrost the PT ports and will modify my away-from-home checklist to decrease the split.
As for the loop, they ran 2 horizontal bores from the front yard to the back the yard. Each was about 150' and had two pipes in the bore when done. They connected them at the end to make what I assume to be two loops for a total of 600' of loop pipe.
How deep is this horizontal loop?
Minimal setbacks with geothermal. You'll drive the loop temps down for a week or more and erase whatever savings you might have gained. Plus on hi stage, the system is less efficient as well. I'd use setbacks for comfort only (most people sleep better with it 1-2F cooler).
I'm not a geothermal expert, but I've been reading a lot on it lately. This early in the winter, that seems like pretty low loop temps. I'd think that you'd still be in the 50's, especially with such a hot summer we had in most of the country. Clearly you had water issues that have been resolved and found a better service company. that's a great start.
I thought 400-600' per ton was a general rule for horizontal, meaning unless you're buried deep, you'd have only 1/3 the loop you need. If you're lucky, 3 tons is oversized and your actually heat loss is only around 2 tons, so you cna get by being a little undersized. But as the wonter rolls along, the loop will get colder and colder until you won't have enough capacity to maintain temperature.
I'd get another ground loop installed... or just live with running heat strips a lot in Jan-Mar.
I think the horizontal loop reached a maximum of 30 feet deep.
Originally Posted by Chris_Worthington
Not enough loop and running temps below freezing, scary !
Might want to address the scary prior to getting the loop issue resolved? Is there Glycol in this loop?
Wouldn't the fact that the loop is too short be the reason the temps are running below freezing? So that would actually be the scary that needs to be addressed first??
Originally Posted by Chris_Worthington
Not sure what Glycol is but there is antifreeze in the line if that's what you're asking about.
It is mixed with water and under the circumstances I would have that level of "antifreeze" checked for piece of mind
Originally Posted by chrisw
Then there is the bigger picture that evolves around cost to fix....
Add a heat source to the loop for heating "When" needed i.e. a boiler with some needed means of switching and mixing....
SkyHeating IMO is going to be able offer the best advise here and it might help for you to add a location for us to hopefully point you in a good direction?
But seriously, you have mentioned leaks, more then likely a "water" make up (Either auto "or" manual), the level of protection at this point ???????
There are certainly some major issues with this installation. I would certainly recomend you add at least one and possibly 2 bore holes of the same length to the system, this should not be to difficult but won't be easy. This will ensure you have enough heat exchanger for your 3 ton system. The only way to ensure there is enough loop is to perform a full manual J heat load and then run that through a loop design program. If you have heat loss numbers and location I can give a pretty close estimate of what you need.
For the loop, you should typically have a 20% glycol/methanol mixture with 80% water, this will give you freeze protection to 15 degrees water temperature so even though the PT ports are cold its still operating inside a mostly normal temperature range. The issue I see is that when the real cold actually hits you will not have a loop that is working well. Typically we design for a maximum low temperature of 28 degrees and ideally shoot for 35 degrees if possible. With horizontal or vertical boring its VERY expensive in my area so there is often no payback above a 30 degree entering water temperature even though it seems very low it only marginally affects performance of most new systems.
As others have said, try not to set your thermostat back, the more consistently you can pull heat from your loop the better it will work, the more you shock it and raise and lower temperatures the quicker the loop will drop the the possibly unsafe zone.
So recap, here is what you need
1. Find your Manual J heat loss and heat gain numbers and post up where you live.
2. Find out what type of antifreeze you have/how much you have, a hydrometer can tell you this or since the loop was reflushed and repressurized the company that did this should tell you.
3. Set thermostat to hold a certain temp all day long and only set back a few degrees at night for now.
4. Post of your EWT(entering water temps) and LWT(leaving water temps) based on outdoor high and low temperatures so we can see how it is performing under normal conditions for the next few days and can possibly guesstimate how well the loop will do this winter. It would also be nice to know what is your entering loop pressure and leaving loop pressure because the 6 degree split you mentioned seems fairly normal, I would typically like to see pressures in the 30's and 40's to ensure there are no additional leaks and the loop is holding pressure.
5. Post model and serial number for your Climatemaster system so we can get more specifics on that unit.
Thanks for all of your help and the detailed information. I have a document from the original contractor that lists "System Loads". Maybe that's what you're asking for w/r/t Manual J:
I know the new contractor put antifreeze in the line and I assume there's a decent amount in there now since it's not freezing up even though it's 27 degrees leaving water temp.
System Loads or Peak Loads are calculated based on a variety of details for an individual residence. Assumed occupancy levels, the number of appliances operating, the number of doors & windows and the tightness of the construction all contribute to the amount of energy required to maintain the thermostat set points given the historical extreme weather conditions in your area.
The peak loads used in this report were provided as listed in the following table.
Zone Heating Load Cooling Load (Sensible) Zone SHF
Zone 1 40,000 Btu/hr 28,000 Btu/hr 0.800
I've set the temp to 70 on emergency heat to give the ground a day or so to stabilize.
Since the new contractor flushed the system and performed a pressure test at 100 PSI that found the leaks, it's been holding steady at 42 PSI.
The unit I have is:
Climate Master Tranquility 30
Two stage digital
And most importantly, where are you located, without that information there is not much to work with.
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