Second hand property with 19yr old GSHP

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MikeSmith

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The property has a 19yr old GSHP with horizontal loop and no info on the system other that what is visible above ground level. Its a 11.2kW AWP system. It's at, or nearing, the end its useful working life. I'm considering proactively replacing it or least have a plan ready to implement. The main concern I have is whether the ground loop was sized correctly and how it can be verified.

I'm the 3rd owner of the property. The property was consented for 268sqm with an attic level designed to convert which brings floor area to 351sqm. It's unknown if this was included in the original design calcs or not. I'm also considering doing a extension of up to 40sqm at some point in the future.

Without discovering a tracer cable or digging up the ground circuit how can I figure out the size of it? Is measuring the volume of the working fluid, assuming pipe size can be determined, a common practice?

I'm already apprehensive about the sizing of the system for a property of this age and size.
 
How long have you owned the property for? If you have lived in it through the winter and observed its performance you should have a good idea of whether the system is adequate or not. If it is just new to you can you wait and see how it performs next winter?

I'm not sure how you could physically investigate the current ground loop and be certain of its adequacy. If you have serious doubts about it I'd be more inclined to replace it, if it can de done without too much difficulty, or go for an air source pump.
 
The property is new to me and yet to spend a winter in it. My greatest concern is that it fails before performance/adequacy can be determined. Hence why I'm trying to do some homework now and be as best informed as I can for when the time comes.
 
Do you have a particular reason to believe that the system was not sized correctly (at least big enough for the initial 268sqm)?

19 years ago (and still today), putting in a ground-source heat pump was not a cheap thing to do. I doubt that whoever decided to go to that large optional expense would have spoiled their effort by cutting a corner on the collector sizing.
 
Can you access the collector manifold to determine the number of loops? On modern hdpe piping the length from the start of the coil is written every metre on the side of the pipe. It may be worth looking at the start and finish of each loop. Older pipe may not have this though. It is unlikely they are jointed anywhere except at the manifold so you may be able to work out the lengths.
 
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I would write an email with all your questions to the Estate agent and ask them to forward it on to the seller.
But I wouldn't overly worry about it. Either it works or it doesn't.
If it's not appropriately sized, then it will be expensive, but it will still heat the house.
 
GSHP's were so rare 20 years ago that anybody installing them was likely doing it as a passion project, if you can get in touch some how they'd probably be delighted to burn the ear off you talking about it, I know I would about any of the solar panel or heatpumps I've had installed in houses over the years.

Is there a flow rate meter and flow/return temperature gauges on the loop? If there are then you can easily calculate the 'size' of the loop in-terms of its ability to collect heat, which is ultimately the relevant figure here not the length/diameter of the pipes. You'd need to do some reading on how to collect this accurately though.

If you are going to replace it you'll probably want to consider if a GSHP makes sense next time. With ASHP's being installed in such numbers across the country they're a much safer bet in-terms of accessing servicing, so may well end up with a lower total cost of ownership. A 16kW ASHP is an off-the-shelf item for most plumbers these days.
 
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