Ground Temps

Depending on the layout, I'm trying to change how you look at these things.

Your EWT is your loop field out, BUT your heat pump IN.

Your LWT is your loop field in, BUT your heat pump OUT.

So, on most of our systems that would be a temperature difference running through the heat pump. This is a very short run in most cases - say 10'. Ignoring the fact that it is plumbed to 100's of feet on the other end.

If you have an internal building loop feeding a few heat pumps, then it may be eventually picking up building heat if left to run long enough.

So if your heat pump isn't running, there is very little that would change the temperature in that short of run outside of instrumentation error or some plumbing setup I can't seem to fathom right now.

It is not so much - why is it coming back colder than what is heating it back up before going back down?

When I see this, I think instrumentation error as I know how off some tridicators become over the years.

 

Ongoing Temp concerns

Well basically the water coming back up from the field continues to be colder than the water going down regardless of if I am in heating or cooling mode. Typically 1 to 2 C colder than whatever my system creates.

Yes I have more than 1 heat pump, and yes 1 or more unit has gone into cooling mode and returning heat into the circuit occasionally as we have luckily had a warm week of temperatures significantly higher than historical averages. In addition I have been firing up my boiler to supplement heat requirements. Today, at 2 pm I was seeing +7 C going down and +5 C coming back up.

Obviously for the water up to swing as much as it does, following step for step whatever I put down into the ground, is an indicator of frozen or exhausted field.

I calculate it is not un-expected for this to be the case. We are in middle of February. and I have had no significant heat added to the field for more than 3 months. Yet I have been pulling heat from it 24/7 since early November.

Thanks all for your thoughts and efforts in helping me with my questions.

 

My EWT and LWT

If you look at this chart of EWT and LWT covering from Tuesday Morning thru to Friday at Mid-Day, you will see that my LWT, which is blue in this image, jumps around a lot, responding to heating/cooling cycling of my heat pumps. You can see that the EWT or temp of water coming back up from field is smoother as it is slower to change over same time periods. However, you will note that the temps are always colder for the EWT.

As you can see, the mid-day temps are higher on LWT as my building heats up from lights and people, and my heat pumps switch to cooling, returning heat back to water. This is the typical daily swing, but 2 weeks ago when we had colder temps, I was looking at - 2 C LWT and - 4 C EWT.

 

Weather

and this is our forecast...

 

With glycol available at below 5C at the same time as a cooling load, check into hydronic coils - firing up a compressor to meet a cooling load in Edmonton in mid winter seems the height of folly...