GSHP - Pipework

[Riddler266]

We've just got plans passed for a new build on our property. We are demolishing and building where an existing stable is, and building a new wooden stable in the field. We want to install a ground source heat pump, and I have a couple of questions..

 

1. In the house I've seen a Bosch unit which is a Combi and contains a tank. It looks about the size of a tall fridge freezer - is this the only internal plant needed?

 

2. The pipework. The first job for us is to build a new stable and sand paddock in the field - then clear the site to build the house. I thought this would be an idea opportunity to bury the coils under the new sand paddock and possible under the new concrete pad for the stable also? I've read that they recommend 2-3 times the area of all the floors square footage being under floor heated. This only equates to 1/3 of the sand paddock area, so we should be good.

 

So my thought is to acquire the correct type of pipework and have this buried whilst building the new paddock. Then next year when we start the house it should be a case of connecting up to these and we're good to go. Is there anything wrong with that approach?

 

Thanks for any advice.

 

Rob

 

PS - Architect has also recommended onsite sewerage management (ie not connected to mains) does anyone have any tips for this too?

 

PPS - I'm sure I'll have LOADS of questions as we go through this, it's our first experience of eco homes and self build!!

[Jeremy Harris]

Welcome.

 

Have you priced up a GSHP and compared it to an ASHP?

 

When I did the comparison, the GSHP was going to cost between 3 and 4 times more money than an ASHP, and not give any useful running cost saving through life, because the additional maintenance costs outweighed the very tiny saving from the slight improvement in efficiency.  We switched away from a GSHP during our build, and fitted a small ASHP, and find it's reaching about the same efficiency level as we were quoted for a very much more expensive GSHP.  Ours always runs with a COP of over 3, usually around 3.5, and the running cost is comparable with mains gas (mains gas not an option for us as we're off the gas grid).

 

If you don't have access to mains drainage, then a treatment plant is now pretty much the only option.  Easy to install, but they do need a leach field drain, or discharge to a stream or other flowing watercourse (in England and Wales, SEPA have slightly stricter rules in Scotland) or a drainage mound.  Best to work out where you can both site the treatment plant and the arrangements for its drainage system early on, as there are building regs requirements around where you can place it, relative to the house, boundaries etc.. 

[BotusBuild]

Riddler,

@Jeremy Harris's comments notwithstanding (which I agree with), your proposed approach to installing the ground pipework first and then connecting when you are ready is a very common approach.

 

Some comments:-

Try to avoid putting them under anything that will end up as a solid surface like "the new concrete pad for the stable", just in case there is a problem in the future and you need to access it (unlikely, but it falls in the "you never know what might happen" category and you state you have plenty of other ground to work with anyway)

Regarding the tank in the Bosch unit, I am assuming that is the hot water integrated tank? For your underfloor heating, you may need to consider a buffer tank as well.

I recommend that you do not go by the rule of thumb for the coils in the ground - get someone with experience and the right design tools to determine what it is you will need. Fo this they will need a good set of plans and details of build to determine heat losses of the dwelling.

 

Welcome to the site and good luck with your build

[joe90]

I agree with @Jeremy Harris about the cost of GSHP, even though I have my own JCB and could do all the digging etc it still did not stack up financially compared to an ASHP. With regard treatment plant I installed a Vortex which can discharge to a ditch that is dry part of the year as long as you use a rumble drain to connect tank to ditch.

[SteamyTea]

GSHP's are really water source heat pumps, so putting an impermeable barrier, like concrete over them is not the best idea.

Sand above them s good though. 

[Onoff]

@Barney12, do I recall you digging and laying pipes for a GSHP?

 

Did it ever progress to connecting the loop to anything?

 

Apologies if it wasn't you.

 

(I'd dig one if I had a digger as I've got the land. For no other reason than to get out of the house, make a mess and pi$$ SWMBO off (even more). Win, win, win afaic! ? )