Ashp on insulated raft

[JackofAll]

Hi, for those who have fitted an ashp on an insulated raft what way did you route the pipes, down and under eps coming up inside or through the wall?

[IanR]

Under the raft in a twin pipe, pre-insulated duct.

[JackofAll]

34 minutes ago, IanR said:

Under the raft in a twin pipe, pre-insulated duct.

Thanks @IanR , was thinking that  Ashp would need to be connected using copper pipe hence the question, as copper wouldn't lend itself to bending too well in this scenario.

[Dreadnaught]

On 12/02/2023 at 20:07, IanR said:

Under the raft in a twin pipe, pre-insulated duct.

 

Same here.

[JackofAll]

1 hour ago, Dreadnaught said:

 

Same here.

How far out from the external wall does the pipe exit the ground/path? Not sure if there is a standard distance for heat pumps to be out from a wall or it varies from manufacturer to manufacturer, hence the question.

[Dreadnaught]

I think it depends on where you are choosing to site your heat pump. In my case, as I am choosing to ground-mount my heat pump so the insulated double pipe emerges about 1500mm away from the external wall of my dwelling adjacent the chosen ground-mounting location. However, if I had chosen to mount it on the external wall, I would have arranged for the insulated pipe to emerge in a location suitable for that.

 

I am just this week doing the planning for constructing the heat-pump's base, which is a surprisingly complicated exercise, requiring precise locations for that insulated pipe, but also a small soak away drain underneath the heat pump, plus two concrete piers for the anti-vibration feet to be mounted, and the runs for the duct for the electrical supply and control cable. The insulated pipe and the two ducts are all in place under the raft but I may dig them up again where they emerge from the raft and finely adjust their routes a bit so that they emerge exactly where I need them under the heat pump base. 

[JackofAll]

7 minutes ago, Dreadnaught said:

I think it depends on where you are choosing to site your heat pump. In my case, as I am choosing to ground-mount my heat pump so the insulated double pipe emerges about 1500mm away from the external wall of my dwelling adjacent the chosen ground-mounting location. However, if I had chosen to mount it on the external wall, I would have arranged for the insulated pipe to emerge in a location suitable for that.

 

I am just this week doing the planning for constructing the heat-pump's base, which is a surprisingly complicated exercise, requiring precise locations for that insulated pipe, but also a small soak away drain underneath the heat pump, plus two concrete piers for the anti-vibration feet to be mounted, and the runs for the duct for the electrical supply and control cable. The insulated pipe and the two ducts are all in place under the raft but I may dig them up again where they emerge from the raft and finely adjust their routes a bit so that they emerge exactly where I need them under the heat pump base. 

Our plan is to fit it in line with the plant room however many mm out from the external wall so should be a short enough run, but runs like that may not lend itself well to sharpish bends especially with the twin wall insulated pipe. Possibly the only downside I see with insulated rafts(could be wrong though) is that all pipe locations need to be spot on.

[Dreadnaught]

5 minutes ago, JackofAll said:

but runs like that may not lend itself well to sharpish bends

 

Yes, the anaconda-like insulated double pipe is very difficult to bend. To take it from horizontal to vertical as it emerges from the ground, it needs to dive down deep before bending up so as to emerge vertical given its poor bend radius. Quite difficult to achieve. My pipe has 2x32mm MDPE pipes within it, so bigger than the typical one. My run under the raft is about 12m long so I wanted the larger diameter of pipe to ensure the pipe's flow resistance remained low.

Edited February 14, 2023 by Dreadnaught

[JackofAll]

19 minutes ago, Dreadnaught said:

 

Yes, the anaconda-like insulated double pipe is very difficult to bend. To take it from horizontal to vertical as it emerges from the ground, it needs to dive down deep before bending up so as to emerge vertical given its poor bend radius. Quite difficult to achieve. My pipe has 2x32mm MDPE pipes within it, so bigger than the typical one. My run under the raft is about 12m long so I wanted the larger diameter of pipe to ensure the pipe's flow resistance remained low.

32mm is big, for some reason would have thought 22mm or so would be the norm, kinda get where you're coming from, I also thought that if the temp requirement is high the diameter of the pipe would need to be bigger, think I read that somewhere.

[Dreadnaught]

45 minutes ago, JackofAll said:

Possibly the only downside I see with insulated rafts(could be wrong though) is that all pipe locations need to be spot on.

 

Yes, true. I spent ages planning out all the penetrations, etc., with help from experts. And then those that poured my raft submerged two of them under the concrete, requiring a bit of remedial SDS work to find them again. Having said that, they did a good job with my raft overall.

 

I put all my hot and cold pipework in the raft. One pipe, for cold water, has come out in a slightly wrong location, a bit far from the wall. I am told it is possible to chip away at the concrete and wiggle the pipe in to its correct position and then make good with some self-levelling compound or sand-and-cement. Haven't done it yet though.

[Nickfromwales]

2 hours ago, JackofAll said:

Our plan is to fit it in line with the plant room however many mm out from the external wall so should be a short enough run, but runs like that may not lend itself well to sharpish bends especially with the twin wall insulated pipe. Possibly the only downside I see with insulated rafts(could be wrong though) is that all pipe locations need to be spot on.

No pain, no gain  "If it was easy......."

 

1 hour ago, JackofAll said:

32mm is big, for some reason would have thought 22mm or so would be the norm, kinda get where you're coming from, I also thought that if the temp requirement is high the diameter of the pipe would need to be bigger, think I read that somewhere.

Temp has zero to do with it. It's about hydraulic resistance, and the resultant flow rate in l/p/m. Most ASHP's require a minimum l/p/m of circulation for them to switch on.

[IanR]

11 hours ago, JackofAll said:

How far out from the external wall does the pipe exit the ground/path? Not sure if there is a standard distance for heat pumps to be out from a wall or it varies from manufacturer to manufacturer, hence the question.

 

Your heat pump should have a minimum distance from a wall. Orientated "back to the wall" so blowing away from the house, mine had to be a minimum 150mm from the wall, which seems really tight. I went with a position where the ASHP is 500 from the wall, and brought the pipes up in between it and the wall, towards one end.

 

I also went with the Ø32 twin pipe in a Ø150 duct (Rauvitherm from Rehau). From memory it was an R750 bend radii, so the trench does need to be quite deep. Penetrations through the raft should come through perpendicular, so my trench was at least 750mm under the bottom layer of EPS. 

 

My ASHP states Ø22 Min for the flow and return pipes. The installers wanted the Ø32, and as I have a longer route than ideal to the UVC and Buffer, I was happy to go with it.

 

11 hours ago, JackofAll said:

 Possibly the only downside I see with insulated rafts(could be wrong though) is that all pipe locations need to be spot on.

 

I placed the pad for the ASHP after the pipes were installed, so no issue with pipe positioning on the outside. Within the house, it depends on your construction method and how flexible it is to accommodate out of position services, but that does for all penetrations, not just the ASHP. Foul drains to toilets and showers gave me the biggest head aches as the tend to be close to a wall so more of an issue if they are 50mm out of position.

[jack]

On 12/02/2023 at 19:58, JackofAll said:

Hi, for those who have fitted an ashp on an insulated raft what way did you route the pipes, down and under eps coming up inside or through the wall?

 

We had to route our ASHP pipework from one side of an attached double garage (on a raft) to the other and then a couple of metres through the house (also on a raft) into the plant room.

 

The insulation under the slab is 3 x 100 mm EPS, so I got the guys doing it to leave a pair of channels in the middle layer. I laid some cheap drainage pipe (50 mm?) in the channels and used some expanding foam to hold them in place. They then did the last layer of EPS and proceeded as normal.

 

I used a block of offcut EPS where the duct came into the plant room to keep the concrete away from the duct when it was poured. Once the concrete cured, I broke out the EPS, leaving me with a duct entering an open chamber in the slab at the edge of the plant room.

 

When it came time to install the heat pump, I threaded 32 28 mm Hep2O (with oxygen barrier) piping through the duct. A 90 degree elbow in the chmaber and we had our flow and return in the plant room.

 

At the ASHP side, I used elbows to come up the side of the garage wall. This is one detail I don't think I gave enough thought to at the time. I should probably have converted to copper right as the pipe came out of the EPS, and done everything from there in copper and then stainless braided flex, but we went with plastic. I was concerned about rodents etc, but it's pretty well wrapped in insulation and nothing's ever shown any interest in it.

[JackofAll]

15 hours ago, Nickfromwales said:

No pain, no gain  "If it was easy......."

 

Temp has zero to do with it. It's about hydraulic resistance, and the resultant flow rate in l/p/m. Most ASHP's require a minimum l/p/m of circulation for them to switch on.

No pain... very true I guess, re hydraulic resistance will need to look at more heat geek videos 🤓 to be honest I glaze over at some  technical info, it's like a whole other language and sometimes feel that I ain't wired to understand.

Edited February 15, 2023 by JackofAll

[JackofAll]

6 hours ago, IanR said:

 

Your heat pump should have a minimum distance from a wall. Orientated "back to the wall" so blowing away from the house, mine had to be a minimum 150mm from the wall, which seems really tight. I went with a position where the ASHP is 500 from the wall, and brought the pipes up in between it and the wall, towards one end.

 

I also went with the Ø32 twin pipe in a Ø150 duct (Rauvitherm from Rehau). From memory it was an R750 bend radii, so the trench does need to be quite deep. Penetrations through the raft should come through perpendicular, so my trench was at least 750mm under the bottom layer of EPS. 

 

My ASHP states Ø22 Min for the flow and return pipes. The installers wanted the Ø32, and as I have a longer route than ideal to the UVC and Buffer, I was happy to go with it.

 

 

I placed the pad for the ASHP after the pipes were installed, so no issue with pipe positioning on the outside. Within the house, it depends on your construction method and how flexible it is to accommodate out of position services, but that does for all penetrations, not just the ASHP. Foul drains to toilets and showers gave me the biggest head aches as the tend to be close to a wall so more of an issue if they are 50mm out of position.

@IanRAm dreading showers especially the fitting of bases, will probably need to make up a 2x frame or 50mm piece of Pir or the like to countersink the bases. Am worried that we'll omit some duct or other, go over the plan enough times and we should be OK I guess.

Edited February 15, 2023 by JackofAll

[JackofAll]

4 hours ago, jack said:

 

We had to route our ASHP pipework from one side of an attached double garage (on a raft) to the other and then a couple of metres through the house (also on a raft) into the plant room.

 

The insulation under the slab is 3 x 100 mm EPS, so I got the guys doing it to leave a pair of channels in the middle layer. I laid some cheap drainage pipe (50 mm?) in the channels and used some expanding foam to hold them in place. They then did the last layer of EPS and proceeded as normal.

 

I used a block of offcut EPS where the duct came into the plant room to keep the concrete away from the duct when it was poured. Once the concrete cured, I broke out the EPS, leaving me with a duct entering an open chamber in the slab at the edge of the plant room.

 

When it came time to install the heat pump, I threaded 32 mm Hep2O (with oxygen barrier) piping through the duct. A 90 degree elbow in the chmaber and we had our flow and return in the plant room.

 

At the ASHP side, I used elbows to come up the side of the garage wall. This is one detail I don't think I gave enough thought to at the time. I should probably have converted to copper right as the pipe came out of the EPS, and done everything from there in copper and then stainless braided flex, but we went with plastic. I was concerned about rodents etc, but it's pretty well wrapped in insulation and nothing's ever shown any interest in it.

@jack so your flow and return comes out the side of the upstand?, that seems a good idea rather than digging down like IanR did.

[jack]

3 minutes ago, JackofAll said:

@jack so your flow and return comes out the side of the upstand?, that seems a good idea rather than digging down like IanR did.

 

I knew I'd done a sketch, but apparently I did one in quite a lot of detail!

 

 

You do need to think about how you're going to neatly finish this area, as well as ensuring the EPS is protected from rodent attack.

[JackofAll]

3 minutes ago, jack said:

 

I knew I'd done a sketch, but apparently I did one in quite a lot of detail!

 

 

You do need to think about how you're going to neatly finish this area, as well as ensuring the EPS is protected from rodent attack.

Expandable metal and plaster down? Hadn't thought about that to be honest.

[jack]

13 minutes ago, JackofAll said:

Expandable metal and plaster down? Hadn't thought about that to be honest.

 

There are a few discussions on BuildHub about how to finish off the EPS upstand (generally, not just where things pop out). Take a look at these threads (and links to other threads they contain):

 

 

 

[JackofAll]

1 hour ago, jack said:

 

There are a few discussions on BuildHub about how to finish off the EPS upstand (generally, not just where things pop out). Take a look at these threads (and links to other threads they contain):

 

 

 

Thanks Jack, several options there, will probably go with the cement board one and plaster over, due to planning requirements, I do fancy brick slips though, they'd look the job.