GSHP horizontal collector idea

Superdaddy

Was just reading another thread on A2WHP v GSHP. It got me thinking of cost saving ways to install the horizontal collector for a GSHP. I am just throwing this idea out there, don't shoot
I am building what should be an A2 rated house at the moment. I am putting in a septic tank and with that I have quite a large percolation area (400m2 divided into two beds). If I was to lay the horizontal collector under the percolation it would save a lot of digging. Can anybody see a reason for not doing that or why it wouldn't work?
I was also considering that where you have bacteria breaking down waste, you also have heat, did you ever put your hand into a compost heap? Percolation areas have massive amounts of bacteria in the soil breaking down the waste, the heat generated could be part of the reason grass grows so vigorously over percolation areas. Perhaps this could also help the ground temperature and reduce running costs?
Is the collector for a GSHP the major price difference with A2WHP?

Strolling Bones

Superdaddy wrote: »

Is the collector for a GSHP the major price difference with A2WHP?

It is - and I am intrigued by your query - often wondered my self.

KCross

Superdaddy wrote: »

Was just reading another thread on A2WHP v GSHP. It got me thinking of cost saving ways to install the horizontal collector for a GSHP. I am just throwing this idea out there, don't shoot
I am building what should be an A2 rated house at the moment. I am putting in a septic tank and with that I have quite a large percolation area (400m2 divided into two beds). If I was to lay the horizontal collector under the percolation it would save a lot of digging. Can anybody see a reason for not doing that or why it wouldn't work?
I was also considering that where you have bacteria breaking down waste, you also have heat, did you ever put your hand into a compost heap? Percolation areas have massive amounts of bacteria in the soil breaking down the waste, the heat generated could be part of the reason grass grows so vigorously over percolation areas. Perhaps this could also help the ground temperature and reduce running costs?
Is the collector for a GSHP the major price difference with A2WHP?

I have my horizontal collector under my treatment unit percolation area. No issues with it and was advised to do it by the installer.

I think the main benefit is that the water being pumped into the percolation will give heat to your collector as it filter down passed the pipes. I'd imagine the amount of heat will be minimal but it will help particularly in dry, cold conditions.

One potential downside is that a leak in your collector might mean having to dig your percolation area. Should be a very very small chance of that happening though.

Superdaddy

KCross wrote: »

I have my horizontal collector under my treatment unit percolation area. No issues with it and was advised to do it by the installer.

I think the main benefit is that the water being pumped into the percolation will give heat to your collector as it filter down passed the pipes. I'd imagine the amount of heat will be minimal but it will help particularly in dry, cold conditions.

One potential downside is that a leak in your collector might mean having to dig your percolation area. Should be a very very small chance of that happening though.

Great to know it has been done, could use the same trench back to the septic tank and then back to the house too. It has to be a major saving. Did it save you much going this route? And as you say there is a constant water supply over the pipes too.
It wouldn't be a pleasant one to dig up for a leak alright. I'd say you'd cut your losses and dig an new trench.:)

KCross

Superdaddy wrote: »

Great to know it has been done, could use the same trench back to the septic tank and then back to the house too. It has to be a major saving. Did it save you much going this route? And as you say there is a constant water supply over the pipes too.
It wouldn't be a pleasant one to dig up for a leak alright. I'd say you'd cut your losses and dig an new trench.:)

It didn't save me much (if anything) as the way my build worked out the collector and treatment unit went in many months apart. If you can organise to have them done together then it will save you having to get a digger back onsite but it might be difficult to get them organised at the same time.

Also , I wonder if it would be better to let the ground above the collector settle before you put in the percolation area?

Calahonda52

Just asking here: typically what depth is the percolation area and then what depth is the ground loop relative to ground level?

Strolling Bones

Calahonda52 wrote: »

Just asking here: typically what depth is the percolation area and then what depth is the ground loop relative to ground level?

Both depending on geo survey but 900 / 1200 I would guess respectively

Strolling Bones

Calahonda52 wrote: »

Just asking here: typically what depth is the percolation area and then what depth is the ground loop relative to ground level?

Both depending on geo survey but 900 / 1200 I would guess respectively

Calahonda52

Thanks, if the GL is too far down then I have read that it will only chill the ground which won't re-heat from the sun.

The idea brings a new dimension to Reduce Reuse Recycle.

KCross

Strolling Bones wrote: »

Both depending on geo survey but 900 / 1200 I would guess respectively

Yes, collector about 1m down
The percolation area can be at ground level or you could have a raised percolation area. Your planning might stipulate raised depending on soak test.

Condenser

Superdaddy wrote: »

Was just reading another thread on A2WHP v GSHP. It got me thinking of cost saving ways to install the horizontal collector for a GSHP. I am just throwing this idea out there, don't shoot
I am building what should be an A2 rated house at the moment. I am putting in a septic tank and with that I have quite a large percolation area (400m2 divided into two beds). If I was to lay the horizontal collector under the percolation it would save a lot of digging. Can anybody see a reason for not doing that or why it wouldn't work?
I was also considering that where you have bacteria breaking down waste, you also have heat, did you ever put your hand into a compost heap? Percolation areas have massive amounts of bacteria in the soil breaking down the waste, the heat generated could be part of the reason grass grows so vigorously over percolation areas. Perhaps this could also help the ground temperature and reduce running costs?
Is the collector for a GSHP the major price difference with A2WHP?

I wouldn't recommend it. If you have a problem with either you'll lose both. Problems with collectors are rare but problems with percolation areas are not. There are no real benefits from siting it under a percolation and could even be a problem if the soakage is on the slow side.
The cost difference would be minimal also, you might save yourself €1k on the average house and probably not even that.

KCross

Condenser wrote: »

I wouldn't recommend it. If you have a problem with either you'll lose both. Problems with collectors are rare but problems with percolation areas are not. There are no real benefits from siting it under a percolation and could even be a problem if the soakage is on the slow side.
The cost difference would be minimal also, you might save yourself €1k on the average house and probably not even that.

Condenser
Having a problem with the percolation area wont result in loss of the collector unless you have a really inept digger driver!

My percolation area is several feet above the collector. The percolation area is an area of small stone with a sheet and pipes on top of that and then more earth on top of that. It is easy for a digger driver to know they are at the bottom of the percolation long before they see a collector pipe.

If the percolation area developes a problem you can safely dig that without going anywhere near the collector.

I would agree the savings are small. I didnt do it for money reasons.... it was really a space issue..... I have a large collector area and the percolation areas arent small either so it is difficult to find dedicated space for both and your percolation area is more or less dictated for you at planning stage.... I chose to put my percolation on top of the collector because it suited and there wasnt much downside.... the worst case scenario is that the collector has a problem and I lose both in that case. Calculated risk.

Superdaddy

KCross wrote: »

My percolation area is several feet above the collector.

When you say several feet, how deep do you mean? Just curious as to why it would need to be several feet beneath the percolation, would 300-500mm not do? Especially if the percolation is already covered by 1000-1500mm of soil.
I agree with you that it is a calculated risk. Does the collector have to be laid level? Or could it be run up and down a slope?

KCross

Superdaddy wrote: »

When you say several feet, how deep do you mean? Just curious as to why it would need to be several feet beneath the percolation, would 300-500mm not do? Especially if the percolation is already covered by 1000-1500mm of soil.
I agree with you that it is a calculated risk. Does the collector have to be laid level? Or could it be run up and down a slope?

The collector is 1m down. The percolation is fairly close to ground level. So, there is a few feet between them.

I believe the collector needs to be in or around the 1m mark. You can put the percolation as near or far to the collector as you want but obviously too near and you risk damaging it with diggers.

My percolation happens to be near ground level. The planners decided I should have a "raised percolation" area so it is near ground level with enough top soil on top of it to grow grass.

I'm not sure about how level a collector has to be. Condenser might know.

Condenser

Depends on the collector type. A Dx or direct evaporating collector should be as level as possible.
A glycol collector doesn't have to be level at all, the pump could possibly be ran slightly lower in speed if its level.

FWIW I would keep them separate.