GSHP installation

[LSB]

Hi Guys

More questions

 

 

I've been looking into ASHP v GSHP, the biggest advantage of the latter being it works all year in theory.

 

We have the space, we have the digger to do the trenches so cost not as huge in comparison as it could be.

But all our fields are on a slope, the barn is at the top.

 

Can the slinky be installed on a slope, I don't seem to be able to find out anything about this.

Also would the unit go at the top of the slope nearest the barn or at the bottom.

 

Also is there any risk if we have the horses in  the field once the trench is filled in and re-seeded or would it be more sensible to fence it off.

 

Slope if about 15 - 20 degrees.

 

TIA

 

[Nickfromwales]

Hi. 
ASHP’s ‘work’ all year round just fine. 
 

Slinky’s can be on sloping ground, no issues there. Unit can be at top ideally, as air rises, or you’ll need to make provision for venting any absolute high point(s). Would need to be a very adverse run to need additional venting, if the unit is at the highest point. 
 

You can have a smash and crash car derby afterwards, the pipe will be over 1m-1.5m down typically so do what you like once installed.

 

Consider where the internal unit would go, as these are not quiet units, and can be quite a cumbersome installation once all necessary gubbings / ancillaries are  installed.

 

Monoblock ASHP’s have everything outside, so ask yourself “why” you need a GSHP first  

[JohnMo]

GSHP slightly higher CoP, but may not have at the tale end of winter, if you have cooled the ground too much.  Not always inverter driven, so may not modulate as much, so will need a buffer.  Generally a big faff, with digging and slinky and filling,  ASHP easy to install.

[Tates]

HI. I installed my own GSHP and love it. Very cheap to run and reliable. Re trenches..... Yes best if pump is on the high side to prevent trapped air as pump runs slow. I went on a course provided by the supplier. Pretty basic but did give a few extra hints. I dug 4 x 50m trenches 1m wide. I was told the pipes must be 1m deep, no more as sun heat wont always get there and no less in case deep frost. I used 'as dug' sand below and above for protection. Half the price of building sand. The wetter the ground the better. Clay is good, chalk or sandy too dry. Gives better conductivity to replace lost heat. Used a 2 ton digger with driver. Took 4 days to dig, lay slinkys and refill. I have no extra heating such as log burners and house is warm enough even in deep winter. Avoid trenches near trees as they will cause shade from sun. 

Been running 6 years now.  AS JohnMo suggested, I have a 200l buffer tank between pump and ufh and rads. Allows the pump to run longer but less frequently. My house a new build, well insulated 300m2+.

[Jimbo37]

I am at the same ASHP vs GSHP decision point, for a new build 200sqm 2 story house - solid floor downstairs, and timber up. Like the OP, I started with the view that GSHP would be a better solution, but the more I read - inculuding this post, ASHP seems to be an equilly decent job - maybe save a bit on install costs, and lose a bit on running costs - do people generally agree with that? Should it suffice for DHW and SH, even with wooden floor?

Edited February 4, 2023 by Jimbo37

[sam]

When I put my gshp in the rhi helped the decision. You would have to do the sums now. In response to the earlier post, you should get the same cop all year if the system is sized appropriately. My kensa says (on the display when it's running) it gives cop of >5 for heating  (38 degrees) and >3 for dhw. How does that compare to a new ashp? Noise is slightly worse than the freezer.

[JohnMo]

Not sure the saving are anywhere near what they used to be (10 to 15years ago) now that an ASHP modulates.  You may get a better CoP on the very cold days with gshp but most other times the ASHP could should be better.

 

Internal house plumbing design, can break any efficiency gain of either HP.

Edited February 4, 2023 by JohnMo
Spelling

[Jimbo37]

I think my staring point will be to get a design and quote for each type, it gets some sort of reference point in place. To my knowledge, there is no RHI (or similar) incentive in NI since 2016 (don’t ask!), so then I can look at the pinch points. I have considered putting back my oil burner with ST to offset DHW, is that just madness (leaving eco argument aside for now)?

[dpmiller]

which bit of BT33 is it? have you actually got enough soil to put a slinky in before hitting bedrock?

[Jimbo37]

Newcastle - dont expect to his bedrock, as there may have to be piles

[SteamyTea]

7 hours ago, Jimbo37 said:

Newcastle - dont expect to his bedrock

Dig deep enough and you may find some coal, all problems sorted then.

[Kelvin]

I have a redundant 137m borehole on my land near the house. Not sure how much heat can be extracted from a single borehole. I assume it depends a lot on the geology. I guess it’s maybe 5 or 6 kW? Anyone know. 
 

I literally never considered using it until reading this thread! 

Edited February 6, 2023 by Kelvin

[SteamyTea]

About 15m to the kW.

So about 9 kW.

 

Does depend on how much water is flowing past.