I'm happy after 16 months of geothermal. We have dual vertical loops. I am thinking about buying surface thermometers for the internal tubes to gauge incoming / outgoing loop fluid temps. My research says that I can install the probe on the outside of the pipe/tube and then insulate heavily over that probe, and get a very close approximation of the ground loop fluid temperature. Of course, it's all data unless I know what temperature the loop SHOULD be reading. Does anyone have any guidelines on what the incoming loop temps should be; and thoughts on where it would be best to install the sensors? Thanks.
Use a needle thermometer in your p/t port, that is the only way to be precise. Everything above 30F in heating dominated climate is fine.
Cooper Adkins makes some excellent reduced tip diameter thermometers that work very well in Pete ports. If your system lacks ports, using metal foil tape to attach a temp probe to a metal pipe fitting should be fairly accurate with a bit of insulation (such as 1/8" peel and stick Armaflex or similar, available at LowDepot)
I agree anything over 30 deg. incoming water for winter is acceptable and under 90 deg in summer is acceptable. We design for 30/90 with our fields in NJ. In your original design from your installer did it not mention the design perimeter's. You should have some kind of inlet Water temp designs, or you can ask the installer what he sized your loop field for. BTW..... Walmart sells inexpensive probe style meat thermometers to do a easy test IF you have P/T ports.
'I agree anything over 30 deg." In fact a field can occasionally dip under 30 and still be functioning correctly.
Agreed. I have seen EWTs drop down to 22F and working properly, However, if you are below 30F now, in heating dominated climate, with still 3 months to go in heating, I would keep an eye on the loop temperatures.
True, but I've never been comfortable with the level of effort needed to ram a conventional meat thermometer probe approx 1/8" diameter into a Pete port. The Coopers reduced tip inserts much more easily, and the accuracy is better. I have a pair of their newest larger display models that track each other to within a tenth Deg*F, very handy for delta-T measurements.
Currently my LWT is 35 - 36 deg after an nights of 6 to 12 deg weather measured in the mornings around 7:15 or so. I measure with a probe in the PT port while the furnace is running. we still have the rest of January and February in North Central Ohio to make it through. 1. will the temperature of my loop continue to drop the longer the HP is in heating mode - because we are continually pulling energy out of the ground? As we are going into the heart of cold water. I am wondering if my system is going to keep up without an alternate source of heat. 2. my HP came with freeze protection based on pressure build up or something like that. I did receive a sensor that I can tape to the exiting tube and then plug into the control board, change the freeze protection jumper and it is supposed to be more accurate - as I understand it, a gauge vs idiot light in a car - I am concerned about making a change to my system this time of year. is having the sensor taped to the hose better than the pressure method?
"I am wondering if my system is going to keep up without an alternate source of heat." If properly designed, a system in a heating dominated climate will employ some auxiliary heat. "my HP came with freeze protection based on pressure build up or something like that." Perhaps you are talking about a low pressure switch? Is there antifreeze in your system? Mark, we call it glycerine, but yes water soluable lubricants are what I was taught to use.
unfortunately for me I did not have a chance to get the AUX coils wired up as of yet. I do still have a wood burner however nothing is automatic switchover. I have 1800' of 3/4" at a depth of 5 feet. my 3t 2 stage has only went into the 2nd stage one time when I increased the thermostat by 2 degrees and it went back to single stage in about 30 minutes. I will be "worry free" once the coils are connected in the mean time I am asking a general question on Geothermal. that is---The more the furnace runs - say this Friday when we have a high of 9 deg and a low of 2 deg, will the loop temp continue to drop? I may proactively use my wood burner or Kerosene to let the loop recover???? or am I not thinking right?
Your loop appears fine. Sit back, relax and have a beer! Normally the industry standard 30/90 design is for entering water temperature, at 35F LWT you probably should have around 40F EWT, which is very good at this time of the year. Yes, it will likely drop further, but those numbers are better than expected for heat dominated climate. No need for a loop rest. The fact that it did not go into normal 2 stage operation at 2F outdoor suggests that the system is oversized for both the heatpump and the loop, which explains the higher the usual EWT this time of the year. Don't forget to put your feet up when you have the beer, I have been told it helps with the loopfield anxiety.
Thanks for the explanation Doc. Someone else on this string may have suggested my 3t system might be over sized (Mr. Custis). perhaps if we kept our house at 72 instead of 65 it would go to the second stage....maybe? For me.. I will have to go straight to bourbon this week given the fact that my Reds stunk in the postseason and I am a Browns fan....that and I do have loop anxiety - thanks for putting a term to symptoms I have belabored with my entire family. So often did I pray for success with my geothermal even at dinner. my youngest son still reminds us to pray for our geo-therm-os. here's to a spectacular new year for all of us!
The colder the loop gets, the MORE heat it is pulling from the surrounding more temperate soil. It's been cold early up north (from what I've read, anyway - only one morning so far this year with visible frost in my part of North Florida) so LWT in the mid 30s for northern OH is likely fine. Assuming it is properly freeze-protected, it'll be fine down to low-mid 20s. That's not ideal, but OK during a cold snap - sole impact is mild loss of capacity and a few tenths reduction in COP. If you are comfortable at 65*F keep it there, but you could probably stand another 3-4 degrees without significant system impact. If I set mine at 65, my wife would move out. Be happy!
