Ground Temps

Does anyone have access to information about expected Temps in a Vertical loop system for my area?

We have 220 foot deep holes, so 440 vertical plus horizontal runs with a 25% Ethanol blend.

The installation is in Edmonton Alberta, so I am trying to get a better feel for what would be expected temps.

 

Geo design software puts your deep earth temp at 43.4F. Operating loop temps are impacted by system design.
We would need BTU load of home, heat pump size and set point to tell you.
Most outfits design for ~30F minimum EWT.
j

 

More on water temps

Yesterday my water was coming back up colder than going down. +4C down and +2C back up so my heat pump was shutting down on freeze coil safety.

 

Clarifications Needed

Yesterday my water was coming back up colder than going down. +4C down and +2C back up so my heat pump was shutting down on freeze coil safety.

Doesn't work that way. Firstly, there is no freeze protection for that range unless you are on open loop and then there are some. So your FP is incorrectly set if it is actually locking out.

You can't add heat to the loop during heating. So you either have gauges reading incorrectly or you are running in cooling mode.

 

Or the flow direction is the opposite of what you think.

.

 

I agree that properly configured closed loop unit shouldn't be shutting down with 36F leaving water.
j

 

Let me explain more clearly

Thanks for your input.

Our system is only 2 winters old. This season has been colder than last, so we have had a few more extreme days than previous years, and for the last 2 months it has been running near capacity with very few warm days to break up the constant heat load.

For a few weeks the Field Temp supply and return numbers were slowly dropping. Last week during a particularily cold group of days I noticed temps coming up from field were colder than return water going down.

At one point they were -2.0 C going down and -3.0 C coming back up.

Since then we had a couple of warmer ( read above freezing days) with lighter heating loads but water is still colder coming back up than going down.

My back-up to the system is a gas fired boiler that is now carrying 100% of the load. So I have shut down my water to water exchanger, the loop is being heated by the boiler and the water to air heatpump is now staying on and not tripping out on freeze alarm.

So I was wondering about the possibility of having frozen our field.

 

Your field won't freeze with 25% ethanol at those temps, but it could slush up.

Are you using permanently mounted temp gauges? Or handheld?

 

Worried

Well I was thinking more of the field freezing not the actual coolant.I know 25% ethanol is good to below -12C and we are running it under some pressure so...

 

Mammoth

I think your piping is not correct.

 

More info

Mammoth,

What size unit are you running on that loop field? Know your heat loss? Photos of the installation?

Something is off, and we just don't have enough information to comment specifically.

 

Clarify My question

What I am specifically asking is:

Field freezing, is a colder temp coming up indicitive of a frozen field?

 

Piping Design.

Mark, Allthough I do not neccesarily agree with the design and controls operation of my system, I am not asking for help with that aspect of my system.

My concern is:
the water is coming back from my field colder than it went down, at a range of temperatures, so I think that means a frozen Field - not frozen transfer media.

I know that with antifreze the "coolant" or "heat transfer media" can often work below 32 F or 0 C, especially with pressurized systems.

What I am asking - regardless of system design, glycol or ethanol or other antifreeze, if it comes back colder than it went down in the winter, what does that mean?

 

Still no

If you were just circulating fluids they would be identical. If the heat pump is on and is heating, then LWT would be lower no matter the EWT.

To add, the fluid being measured is before/after the heat pump. Not before/after the ground loop if we are confusing what is EWT.

 

Just Circulating Fluids

Chris, that is what I am saying, I am just circulating the water and it is coming back up colder.

So does that mean my field is frozen or not?

 

Do you have a desuperheater? Does it have a buffer tank?

Is it possible that you're transferring heat from your domestic
hot water tank into the circulating brine (via the superheater)
and then dumping it into the ground?

I don't think frozen ground is what you're seeing, because
ice has quite good thermal conductivity -- better than water
and better than many soils.

 

The only thing your experiment indicates is that you are taking heat energy from your home and putting it in the ground.
J

 

If you are just circulating the loop fluid, meaning the heat pump is not running, and the loop temp is colder coming out of the ground than the temp going in to the ground, then something is very strange indeed.


How are you circulating the fluid with out turning on the heat pump?

Where are you taking the measurments?

How are you taking the measurements?

How much colder is the water?

 

Answering Dean...

1 - I have more than 1 heat pump and they are independant of my Flow Pumps which maintain the circulation through the field regardless of heating or cooling.
2 - My temps are taken from a set of sensors feeding a computer readout and a set of analog gauges. They are mounted where the pipes enter the mech room, and therefore are actual temps leaving and entering.
3 - My temperature readings vary but the one constant is that regardless of what temp my system is sending down to the field, when it comes back up, it is aprox 2 C colder. Today for example I saw temps +3.6 down and +1.5 coming back. Last Monday, -2.5C going down and -4.3C coming back up.

These temps are all charted, and the system is 2.5 years old. This is our second Winter, and it has been colder and continuous without breaks like last year.

My fear is that I have horizontal runs to my bores that are too shallow allowing cold weather to affect the system temps, or that my verticals are too close together, allowing an exhausting of the fields capacity in of the immediate areas of my bores.

 

Small temperature differences measured with separate sensors are
subject to BIG errors unless the sensors are carefully matched -- at
more than one temperature.

Suggest swapping the sensors. ...is EWT still lower than LWT?

.