Ground loop flow and return temperatures?

[rogermunns]

(WRB09 installed by Mr H. Robinson).

Now that things seem to be settling down I have been able to run for longer periods. But I have some concerns about flow temperatures; after an hour things seem steady at 7.3°C input from ground to the heatpump / 4.2°C out of heat pump back to ground array. I also get a message Po07 as an advisory after about an hour's running. Can people comment on this data, please? I will admit I am short on the ground array (200m² area with 400m of 25mm dia. pipe) but there was really no choice on any of these.

[Baz]

It's like those puzzles - eg dead body in snow field, no footprints or weapon, explain.

From this data I am able to deduce that you are a software developer by profession.
How have I reached this conclusion?

[Richard Owen]

How much pipe do you have out of the ground between the ground loops and the heat pump?

When there's a very low air temperature, I sometimes get a Po07 when the pump switches off at the end of its shift. I have about 15m of pipe out of the ground. I don't get any of those errors when the air temperature is above about 5c.

I've reached the conclusion it isn't anything worth worrying about and one day I'll insulate the pipes.

[rogermunns]

Richard, it's about 14m, although this is in the basement, ambient = 10°C approx. Weather here is nearly always warmer in winter than UK, but not always!

[rogermunns]

Have given up expecting my system as-is to work properly.

A few things are not right: insufficient underground pipe (about 350m), too small diameter pipe (25mm), uncompacted earth above pipes.

Am seeing flow and return teperatures down to 5deg. C or lower.

So I'm buying a gas-fired water heater and will bleed flow from that into the loops.

Does anyone know roughly how many cubic metres of propane are contained in a 13kg bottle? I ask because this gas heater is supposed to use about 0,7cubic metres an hour. And over here a bottle costs €27 (£22). I'm hoping I will not need to use it too much.

[titan]

Have given up expecting my system as-is to work properly.

A few things are not right: insufficient underground pipe (about 350m), too small diameter pipe (25mm), uncompacted earth above pipes.

Am seeing flow and return teperatures down to 5deg. C or lower.

5 deg C is fine, heat pumps COPs are rated at 0 deg C ,  so long as there is a 4-6 deg C  differential between the flow and return heat is being extracted from the ground. If your ground loops are too small they will over time be unable to extract heat and there will be a reducing and finally no differential.

[sam123]

(WRB09 installed by Mr H. Robinson).
after an hour things seem steady at 7.3°C input from ground to the heatpump / 4.2°C out of heat pump back to ground array.

These are excellent values.