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Was driving home this evening when I got stuck in a jam on M25, as I was musing out of the window I noticed an ASHP on a farm building and observed the cable tray running from it to the building which, from where I was, looked crowded. It struck me that we have not made provision for the ASHP connections to the new house as yet and that I should get this aspect of the scheme into my head and onto some drawings.

 

It looks like you need to get two well insulated water pipes, inlet and return, one condense drain, one power cable and probably a control cable, which I guess might be CAT6 or something simpler. A couple of thoughts struck me:

 

  1. Is there any limit to the length of the water pipes?
  2. Is it sensible to put them, the water pipes, into the slab, insulated, or run them outside the building. (I think that things which look like an after thought, such as pipes outside buildings should be designed out if possible)
  3. Can the condense drain run into the soak away or must it be piped to the sewer?

 

Any thoughts anyone.

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Ref No.1 The Samsung manual mentions a recommended maximum run of 25m but I would imagine the advice might differ by make/model.

 

Ref No.2. I think it's @jack that has put his flow and return into an eps channel in the slab which is definitely a great idea. We couldn't do it easily due to our split level so in the end went for a pre-insulated pipe set which enters the slab from outside and runs to the edge of the building below the outside finished level. It was expensive and HUGE and very difficult to get a bend radius on. 

http://www.ebay.co.uk/itm/PRE-INSULATED-UNDERGROUND-INSULATED-PIPE-KIT-DUO-TWIN-PIPE-32mm-/112440664851

We've run a 3 core SWA and 2 CAT5 to the same location.

 

Ref No.3 The Samsung unit we looked at just said that you should have a permeable area below the ashp that the condensation can drain into. 

 

Hope that helps

Edited by Barney12

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1. I think the max pipe length is likely to be manufacture specific primarily based on the pump capacity.

2. We have pre-insulated pipes set into the slab, so no visible nasties. We have also run a couple of Cat5 and a couple of 3 core to the location.

3. No idea what the correct answer  is but ours will soak away directly into the sandy soil below the ASHP.

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Check with the supplier as when you go up past 6kw IIRC some require you going with 28mm not 22mm pipe. 

 

I'm about to move ours as it's caught me out as I forgot the pipes when we did the slab and there is no easy or elegant way to get pipework to the unit without heading up into attic spaces etc or running it in skirting boxes which is my other option. 

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FWIW, I've found that the pump in our re-badged Carrier is a standard variable speed circulating pump.  Our pipe runs are short, less than a metre of 22mm copper, plus 900mm 19mm bore flexible pipes at the ASHP itself.  I had to turn the pump in the ASHP down to its lowest setting, as the flow was far too powerful with it on setting 3.

 

Given that the pump looks to be a standard unit, it may well be possible to substitute a larger one if needed.  The only things inside the ASHP on the water side, apart from the pump, are a standard looking plate heat exchanger, a tiny expansion vessel, a drain cock and an air vent.  All except the plate heat exchanger could be removed and replaced pretty easily, I think.

Edited by JSHarris

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You're lucky @JSHarris - I need to put a pump into ours but the current plan is to get another Wilo like the one on the Wunda manifold as they are near silent. 

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Just resurrecting this thread as we need to future proof in case we decide to install an ASHP.  At the moment the Willis heater is doing a pretty good job of keeping us warm, but we may need some cooling in the summer and that will call for an ASHP. The electrical supply is not a problem but it is the pipe runs that we need a bit more information about. We are just about to have the paving done outside and need to sort the access.

 

The ASHP will need to be installed outside against the shed. The access for the pipe runs go under the slab, this is simply some 110mm soil pipe coming into a 90° bend straight into the utility room.  This is probably going to cause us a bit of grief.  We didn't do our homework on this when the slab was installed and now need to work around this issue so any advice would be welcome. 

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I'm assuming that it's the 90 deg bend that's the potential issue.

 

Is the bend a standard one or a swept one? 

 

If the former then you may really struggle to get insulated 22mm plastic pipe round it, if the latter then it may just get around OK. 

 

One solution may be to terminate some insulated 22mm pipe with a long full bore flexi, test the joints for leaks, insulate the flexis with Armaflex, tape the open end of the flexis to stop muck getting in, then feed the pipes in from outside.  With luck the flexis will just go around the bend in the 110mm pipe easily and just pop up inside, where you can make the internal connections.

 

 

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1 hour ago, JSHarris said:

I'm assuming that it's the 90 deg bend that's the potential issue.

Yes and it's not a swept bend either!

Terry thought maybe we could leave the insulation off that end of the pipe.  I assume we would use the 22mm hep20 stuff with some kind of insulation taped around it.  We could finally fill the 110mm pipe as it comes into the house with expanding foam. The pipe will be under the insulated slab by then anyway. 

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It's a lot easier to use the pre-insulated pipe that's made for the purpose, like this: https://cpv.co.uk/product-range/pre-insulated-pipe/hiline-flex-pe-xa

 

(I'm not recommending this one, it was just the first website with a photo I could quickly find).

 

You won't get 22mm pipe to bend around a standard bend, so I suggest you have a think about the possible solution I suggested above.  You can get 1.5m long large bore flexis, I have them connecting our pressure vessels.  I'm certain that two of those, wrapped with Armaflex, would get around that bend OK.

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10 minutes ago, JSHarris said:

You can get 1.5m long large bore flexis,

 

@JSHarris do you have a link..?? I need a couple that size for my ASHP. 

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15 minutes ago, PeterW said:

 

@JSHarris do you have a link..?? I need a couple that size for my ASHP. 

 

 

I have two spares here, if you're desperate, I'll try and find where I bought them from.

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Right, I've dug back through the emails and found the order.  The hoses came from BES: https://www.bes.co.uk/braided-stainless-steel-flexible-hose-3-4-x-1500mm-8131

 

I used ones with bends on the end as they better fitted the tees on the bottom of the pressure vessels.  I also used shorter ones with bends on (900mm IIRC) on the back of the ASHP, as it made the pipes run in a loop (to kill the transmitted vibration problem) neatly.

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Thanks @JSHarris - what is the outer dimension on the flexi pipes ..? Just wondering if 22mm insulation will fit. 

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9 hours ago, PeterW said:

Thanks @JSHarris - what is the outer dimension on the flexi pipes ..? Just wondering if 22mm insulation will fit. 

 

 

I used 28mm insulation, as 22mm was too tight.  I can measure one of the spares I have and let you know the size tomorrow.

 

Edited to add:

 

@PeterW, I've just found what look to be similar spec, but shorter length, flexis on the Pipestock website.  They give the OD of their 19mm bore, 3/4" BSP fittings, pipes as being 27mm.  My guess is that the BES ones would be the same, as the spec seems to be the same, apart from Pipestock not doing flexis that are that long.

Edited by JSHarris
Added info

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Thanks guys.  You are just juggling so many balls in  the air during design and construction that you are bound to drop one or two.  In this case we used 110mm pipe foulwater pipe as an access path from the service cupboard out beyond the slab.  I mistake that I made was using a normal 87½° bend to bring it up into the service cupboard instead of a Drainage 87.5° Rest Bend, or even a 45° and cutting the stub off at an angle.  The normal bend has a radius at centre of around 110mm and 160 at the outer curve.  This was enough to get a 25mm MDPE DCW feed up the other access pipe.

 

It's really touch and go as to whether installing an ASHP will be cost effective, and there's no urgency.  I was going to wait until autumn when I've seen how the house performs during both winter and summer before making the call.  The issue that we now face if that Jan is now in JFDI mode and wants to get all of the outside paving done by a local contractor including paving over the run where we'd need to bury the pipe. 

 

It's just not worth having to dig up a trench across the new paving, so I guess that the sensible thing to do now is to fork out the £500 or so for the proper insulated pipe and get our paving guy lay it under the paving whether we end up using it or not. 

 

Time get the 9" angle grinder out.  I've got to clear the concrete perimeter up the pipe -- yes, I know that I should have left a length of ESP along the trench line and had the concrete about 25mm depth over it, but again -- a Tardis moment.

 

PS.  Concrete trenching all done and outside of access pipe exposed.  A combination of a 9" Angle grinder with diamond disc and a decent SDS drill to put "stamp tear perforations" across the bit wanted to chop out made fairly easy work of it.

 

As Jan pointed out, the reason for our JDFI (army acronym -- Just F***ing Do It) mode is that we want our VAT back as the paving plan was part of our landscaping and implementing is a planning condition so the work is zero VAT rated if we do it before sign-off. 

Edited by TerryE
Add PS

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Well we've spent the weekend fitting the ASHP pipe according to @JSHarrisrecommendation (thanks Jeremy, great help as always).

Bought the pre insulated pipe that @Barney12 recommended. Stripped off the outer corrugated protection for the part that enters the access pipe. Luckily there was a double layer of insulation and we only needed to remove the first layer.  Then connected the 1.5m flexis. Wrapped them in insulation and then wrapped the stripped back section and the insulated flexis in polythene and duck tape. The pipe fed in pretty easily once we got some rope tied around the corrugated section about two meters back and used it to give us a grip on the pipe and enable us to push it in.  

We can now just get the paving guys to bury the pre insulated pipe to the approximate position for the ASHP.

 

 

 

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Edited by JanetE

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Really glad it went well for you.  Looks like a pretty good job, too, and it should be easy to seal up around that hole. 

 

One thing to watch is rodents.  What I did before sealing ducts with foam was to roll up a ball of chicken wire, thread a bit of stiff wire (I used old coat hanger wire) through and make it secure, then push the chicken wire down the duct, leaving the thicker wire poking up.  Then foam and seal around the pipes in the duct and trim the bit of wire down a bit if need be.  Do this at both ends of the duct.  If you ever need to get the pipes out of the duct for any reason, you can then chip away the foam, grab the stiff wire with a pair of pliers and pull the chicken wire and remaining foam out.

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