Geo not working properly

I have a 3100sf house in West Michigan near Grand Rapids. I had a 4 ton Bosch geo unit install this spring after the heating season had ended. I knew the unit wasn't working right in November and the installer has been working on it since then trying to get it to run correctly. In stage 2 heating at 30°F outside air temperature the unit can't keep up with heating our house to 70°. We have been forced to run with the inline 9.6kW electric strip heaters just to keep the house warm. My last electric bill for December which was 6.2°F warmer than normal was over 4500kWh (3800 - 3900kWh of which is geo related). The calculated load would have had us using about 1600kWh for heating in addition our baseline usage is approximately 700kWh. Needless to say our current bill is as much if not more than I would have paid with my old single stage propane furnace. Our house has 2x6 walls with spray foam insulation and an unheated basement. There are a fair amount of windows but the installer took that into account with the software he used to calculate our heating/cooling load. There are 4 100ft horizontal loops (total of 800ft length) placed 5ft deep. We are getting desperate since we paid a boat load of money for the privilege having the same or higher utility bills. Does any of this make sense?

 

There are 4 100ft horizontal loops (total of 800ft length) placed 5ft deep. We are getting desperate since we paid a boat load of money for the privilege having the same or higher utility bills. Does any of this make sense?

You have to have more than that in the ground. Have to. So, I'm hoping that is 800' of trench not pipe. If not, that is the problem.

But check your entering water temperatures. They'll be a good indication of a short loop or not.

 

I have a 4 ton system and have 900 feet of active vertical bore - the vertical is a bit more efficient so that jumps right out at me as well.

 

What should I expect for EWT temperatures? When the field has had a chance to rest (which is rare as much as it runs) it starts out in the 40° range. After running for a while it gets down to 32° or so. I can check, but I thought it was 100' out and 100' back for 4 loops. I will check the pipe diameter also on what was installed. How much pipe would you expect in this situation?

 

If the EWT doesn't drop below 30° then your loop length is OK

 

Diagnosing via internet is often a fools errand. That said, I wonder if the system may have been left set for open loop water - freeze protection at 30*F instead of 15*F or so typical of closed loop systems.

I'd be curious to know entering and leaving air temperatures when the strip heat isn't running.

 

Can you confirm that you are talking pipe length, or trench length with a slinky? A normal length would be at least 600ft of pipe per ton, in your case at least 2400 ft. How do you measure the temperature? Make sure you get the correct information on your loopfield.

 

I am using a register vent in the kitchen (which is almost directly above the geo unit so it is a short run) for measuring leaving air temperature and it is running somewhere between 86°F and 88°F. The entering air temperature is 68°F if I remember correctly, but that could be off by a degree or two. I have already asked about the open loop vs closed loop setting and the installer said it was correct. I can ask again to confirm.

 

The loop temperature was measured by the installer with a temperature probe placed in a port at the entry point to the geo unit. The pipe length is truly pipe length and not a slinky. It was done with horizontal boring and not an open trench. I am certain it is not 600 ft per ton. I am still trying to get a reply on the actual length of pipe in the ground.

 

No matter what you do, 800ft at 5' depth is not enough to support your 4 ton heatpump long term with a 4 ton load. Yes, you start it up and EWT looks OK, but you will be very quickly down to 20F EWT, depending when you measure it. This will create significantly reduced capacity with much strip heat use, with the unit's coil freezing up or the 15F safety kicking in. I think you are seeing the symptoms of this. Get a needle thermometer, or even better a monitoring system (WELServer.com).

 

Sounds like the prevailing theory is I am severely short looped. How much of a problem is this to fix? Can I get some recommendations on how much loop I should have assuming a 4 ton load on my 4 ton heat pump is really what I have?

 

OK, so I had some misinformation earlier. I have about 410ft of 3/4" pipe per loop with a U bend in the middle for a total of about 1640 feet of pipe plus a 25 - 30 ft run into the house. Sorry for the bad numbers earlier. docjenser said earlier I should have 600 ft / ton. So in this case I would need two more runs of the same length installed to get up to the 2400 feet mentioned. It is really that "simple". Can they go back out and just add two more runs? I know it is more involved than just drill two more bore holes. There is the work of digging around the old connections and connecting two new loops to the circulation system but is that the summary of what is being said here?

 

Now that you know what you have, it is time to buy a thermometer. Buy a good one. I use a Cooper SH66 and I sticky insulation tape the probes to metal piping when possible.

As stated here many times without good data we are guessing.

Mark

 

What jumps out at me is the depth. Why would anyone only go down to 5' if they are directional boring. We generally go down 10-14 feet. 2400 fet of pipe would be minimum for 3/4" slinkies, but a 4 ton with a 55000 btu heat loss and 4, 1"X100' utubes in saturated sand/gravel could be properly sized.
So my questions are what is the nature of the soil, what is the depth of the loops (is it really only 5' or is that just the header) and what is the manual J loss for the home?
Cant determine much without that intel.
j

 

So you have 205' of borehole per ton, equaling 410' of pipe, correct? x 4, correct? what size pipe in the loops and what is the size of the header pipe coming into the house? It does not make sense that your heatpump cannot keep up with the heat, e.g. it must be running all the time, and your loop is still at 32F entering water, when you have your pipes at 5'. The numbers don't match. Don't follow the 600' rule of thumb, you loop might be fine.
So you need a needle thermometer, a good one, as Joe suggested. Otherwise you are wasting time here.

 

Cooper Atkins DFP450W reduced tip digital pocket thermometer - very handy for Pete's ports. Cooper has several other models...key feature is reduced tip

 

So it has been a week and I have collected a bunch of data. My geo is cutting out due to an internal cutoff when the LWT reaches 15°F. So you guessed it, my EWT is low also. This is where it gets ugly. My installer went out of business. The loop guy came out and said he messed up the header and made a change which made things worse. He is now saying there isn't enough loop in the ground and he wants me to pay for his mistake. He was a subcontractor who was directed to put in enough loop for a 4-ton system and now he is saying he didn't, but that the contractor told him what to do. Back and forth they go. Either way I supposedly have 205' of borehole/ton at an average depth of 8 - 10 feet and in places as deep as 20 feet. My ground is mostly sand/gravel at that depth with some clay mixed in.

What is the typical outcome in this situation? The loop guy isn't taking responsibility and the installer is out of business. Should I start looking for another person to come in and clean up this mess?

 

Well, have gun will travel, I meant have tools will travel.

I could run a rescue trip to put boots on the ground if needed. Since I no long race sled dogs western Michigan is not as appealing as it once was this time of year. On the other hand I could stop in Howell and bug Joe and the lovely Mrs. Hardin again. I fixed a system in NJ by phone NYD, lets see what you can show me by internet.

I have spent years defending the HVAC industry and the geothermal sub set for years from hack and wack contractors that make it a tough industry to make a living in.

Do you own tools? If so what? Are you brave enough to fix this yourself if that is possible?

Depending on which story you tell I think you may have enough pipe in the yard to do the job and it is an error in how to pipe the loops that is causing the lock outs.

You can PM me here, email mcustis@centurytel.net or call 440.223.0840.

Can you take and post some near heat pump piping pictures? Do you know what is in the loops for anti-freeze and what % antifreeze to water it is?

I am here tonight. Who knows where Tuesday and starting a Tekmar re-control Wednesday.

Mark

 

A loop sub contractor installs and is paid for what the contractor directs him to install. If it is not enough, he generally wouldn't install more without being paid more.
I'm still not convinced that you couldn't get by on what you have if properly installed. How did they install the header? Did they grout?
Are you sure you are getting down to 15* or do you mean you are shutting off on low pressure? Is the freeze stat configured correctly on your system.

Mark, if you need a place to go we can send you back to Brad's. We have to do load calcs on the entire monstrosity (18k SF) and find out if we can get enough out of the chuckle-headed installer's existing system to cool the house this summer. I've not had a ton of time to spend on it lately.
j

 

Have software will travel

Joe I'll give you a call.

Mark