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Leaky Ground Loops

 
Grounds Source Heat Pump (GSHPs)
Last Post by davef 3 years ago
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 davef
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Topic starter 28/03/2021 6:34 pm  

Hi, Mars suggested I start a new thread as we have had a GSHP for 10 years . The project came about because at last we were put on to mains drainage and this freed up a section of garden where the septic tank was  which gave enough space for the ground loop which was recommended. There wasn't enough room for the more conventional slinky pipe layout. (Subsequently a friend went the borehole route to the ground loop and hit all sorts of snags as the drilling through boulder clay proved to very difficult.)  Our Ground loop was made up of 16 compact collectors (see. photo) in two trenches.  We had to find a local plumber to do the installation but Ice Energy did the commissioning . Performance was excellent from the start and we appreciated the 24/7 warmth as we were retired. The ground loop developed a leak after several years but with 40 compression joints underground and the size of the leak , finding and fixing it was not possible . One attempt took some time to organise and by the time the testing was was undertaken the system had resealed and held 3 bar.  The leak returned a few months later and the rate varied with the water table and the operating time .  Comparing the cost of operation with the previous system (Oil fired boiler ) was not a priority as the comfort increase and the expected increase in oil price in 2012 .

As this is our only heat source as we are looking to change it to an Air source HP because the leak rate some times meant topping up the system in 3-4 days. Cost of replenishment is about £150/ year.  

P1040120 Collectors in postion (2020 08 11 16 08 47 UTC)

 


   
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 George
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28/03/2021 6:55 pm  

Have you considered fitting an auto refill valve to keep the system topped up and pressurised? 

Mitsubishi Ecodan 14kw ASHP + 500l Cylinder


   
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 davef
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Topic starter 02/04/2021 1:06 pm  

@george  No Please tell me more , how do they work where would I get one Thanks Dave f 


   
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 George
(@george)
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02/04/2021 2:38 pm  

You would need to find a plumber that is happy to fit one as depending on what it’s being used for I’ve been told it’s not always legal.

 

something along the lines of this:

https://www.heatingcontrolsonline.co.uk/automatic-filling-valve-with-gauge-p-701.html

 

you can tell it what pressure you want it to maintain and it it will top up the system automatically when needed.

 

I’m tempted to fit one to our system as I have a small leak somewhere that I can’t find and I have to add pressure to our system every month. 

Mitsubishi Ecodan 14kw ASHP + 500l Cylinder


   
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 davef
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Topic starter 03/04/2021 8:08 am  

@george   Thanks for the info, but it is difficult to see how it would work in my situation. The filling point is on the top of the expansion vessel which is 100mm from the ceiling . The top up liquid is in 20 litres container at ground level so it would need a pump circuit to supply to ceiling height and I find that if I can create a vacuum in the expansion vessel it reduces the leak rate. Maintaining any positive pressure at that point will increase the leak rate.   I currently use a long spout watering can and have to climb up to the top up point. I had considered some sort of metering pump which would need an auto air bleed to allow the liquid in, all on 6mm pipe but couldnt identify the bits I would need to do it. 


   
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Mars
 Mars
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22/11/2021 8:31 am  

@davef, did you ever get this resolved?

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 davef
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Topic starter 22/11/2021 9:17 am  

@editor  Hi, the resolution was to abandon the ground loop and install a Global Energy Systems Thurso ASHP which has been performing well since June. The installation included a new double water tank which went in the same space that the GSHP had been but uses the same radiators as the GSHP was feeding.   I managed to sell the GSHP on EBay. They were booked to take 2 days to remove the old system and install the new but only took 1 day. A follow up check found a couple of snagging issues which were dealt with at a second visit and queries about running performance were answered promptly by e mail, so customer service gets some + marks. They are setting up a portal which hopefully will allow some performance monitoring in real time but development work is taking longer than I think they expected.  

Dave F 


   
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