installing rads, chasing into walls and making good, prior to testing

Hi,
I suspect the answer here will be "don't be stupid", but I thought I'd ask to see if there's a feasible solution.
I'm installing my own rads and pipework for a central heating system, but I'm doing it piece meal over time, whilst also decorating/renovating my house.
I'm planning to purchase a Rothenberger wet pressure testing pump so I can pressurise small sections of pipework as per the part L regs to ensure there are no leaks. On top of this, I'm going to try and be careful and ensure that only bent pipes are buried into the wall (not joints) where the tails of the rads disappear into the the wall and reappear under the floor boards.
My question: could I install the radiators with some pipework chased into the wall, then make good the plaster so I can decorate, before the boiler is installed and pressurised?
The main area is the bathroom, where I'd like to tile the floor. I'd have two 22m copper pipes coming from the 1st bedroom, through to the bathroom, and to the 2nd bedroom, which would then be t-d off for the towel rad. Joints would be soldered, and then I"d pressurise with the Rothenberger tester to test for leaks. Could I then go ahead and make good the walls and proceed with tiling the bathroom floor?
... or is this just asking for trouble? I'd only be doing this in the bathroom and the the plaster on the walls, but when the central heating is installed I'd be able to lift floorboards in all other rooms except the bathroom.
As much as I'd like to just get the job done in a weekend, I don't actually have the funds to get the boiler connected right now, and as temperatures are going to increase over the next few weeks, I'd rather get the place presentable and tackle the central heating a bit later. But if possible I'd prefer to to at least lay the ground work to avoid larger upheaval later on.
What do you think?
Cheers imanc
--
imanc


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I used a bicycle pump.

Avoid copper coming into contact with plaster - the plaster will corrode it if any moisture is present, and water pipes (even heating pipes) will get condensation on them at times. I sleaved 15mm copper pipe in 20mm plastic electrical conduit when plastering into a wall, and you can apply small bends to this combination with a 22mm pipe bender (20mm electrical conduit bender would probably work even better). This also allows for the copper to move a bit as it heats and cools.

This is standardly done when installing underfloor heating in concrete. Indeed it should be pressurised whilst the concrete sets, so the pipes don't later try to expand more than the original holes they formed in the concrete.
I pressure tested all the sections of my central heating as I went. I did it dry which is potentially quite dangerous - if something does fail and blow apart, the energy release can be considerable and explosive and people can be injured, so I made sure I was the only person in the house when doing it. The advantages are that air leaks much faster from any leaks so you can find smaller leaks than you can with water, using gas leak detector fluid (froths up), and if you need to resolder anything, the pipework is still all dry.
Strictly speaking, you should fill most of the system with water when pressure testing, and just have a small plug of air which is compressed. This is because the energy stored in the system, and the potential for explosive release of it, is very much reduced. This is what H&S requires, but it is not so effective at finding small leaks, and more difficult to do on incomplete sections of the system.

I did similar, but actually started with the boiler and just the bathroom radiator. Next came the upstairs heating zone, and finally (a year later IIRC), the downstairs heating zone.
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Andrew Gabriel
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- Avoid copper coming into contact with plaster - the plaster will corrode it if any moisture is present, and water pipes (even heating pipes) will get condensation on them at times. I sleaved 15mm copper pipe in 20mm plastic electrical conduit when plastering into a wall, and you can apply small bends to this combination with a 22mm pipe bender (20mm electrical conduit bender would probably work even better). This also allows for the copper to move a bit as it heats and cools. -
Yes I'd intended to wrap the pipes in denso, secure them with pipe clips, then cover the hole with a layer of expanded mesh steel and plaster over that. Some have said that putting pipe into a plastic pipe will lead to clicking - have you noticed that?
-
This is standardly done when installing underfloor heating in concrete. Indeed it should be pressurised whilst the concrete sets, so the pipes don't later try to expand more than the original holes they formed in the concrete.
I pressure tested all the sections of my central heating as I went. I did it dry which is potentially quite dangerous - if something does fail and blow apart, the energy release can be considerable and explosive and people can be injured, so I made sure I was the only person in the house when doing it. The advantages are that air leaks much faster from any leaks so you can find smaller leaks than you can with water, using gas leak detector fluid (froths up), and if you need to resolder anything, the pipework is still all dry.
Strictly speaking, you should fill most of the system with water when pressure testing, and just have a small plug of air which is compressed. This is because the energy stored in the system, and the potential for explosive release of it, is very much reduced. This is what H&S requires, but it is not so effective at finding small leaks, and more difficult to do on incomplete sections of the system.
I did similar, but actually started with the boiler and just the bathroom radiator. Next came the upstairs heating zone, and finally (a year later IIRC), the downstairs heating zone. - Did you have any issues getting a heating eng to install a boiler and then leave you to do the radiators? I'd assumed they'd want to see a full set up of rads and pipework, prior to installing the boiler.
--
imanc


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On Saturday 09 March 2013 22:08 imanc wrote in uk.d-i-y:

I can't follow any of that - which bit did you write?
Polite request - can you fix your quoting please?
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imanc wrote:

Since I DIY, it's not gospel, but I can't see it really being their concern; they're only there to sort out the gas side of it.
Scott
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I installed it all myself. At the time, it was impossible to find a heating installer who knew anything about condensing boilers. It was before they became mandatory, and the main market was DIY installs and housing associations, so the manufacturers had to be helpful to you or they didn't sell any.
At that time, Keston offered a service to commission DIY installs, but they wouldn't do the install themselves. I was going to use that as a backup if necessary, but I didn't need it in the end. Since I had my own flue gas analyser, they told me over the phone how to set it up for best operation (which isn't in the installation and commissioning guide).
If you plan on having the boiler installed, I would start by finding an installer willing to do this, and get your proposed location for the boiler OK'ed by them. What they'll be most afraid of is connecting up your pipework, and finding a new fountain in every room ;-) Alternatively, get them to install the boiler with one radiator in the same or a nearby room, and expand the system from there yourself.
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On 10/03/2013 10:04, Andrew Gabriel wrote:

In reality its not going to be that different from their PoV from installing a replacement boiler where the rads pre-exist. All they really need do is quote on the basis that the figure does not include any scope for leaking rads etc. Its a less complicated situation than commissioning a boiler installed by someone else.
--
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John.
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Chasing pipework in and just plastering/cementing over is a bad idea. Leads to all sorts of problems. Corrosion, expansion contraction, wall finish cracking etc. You can sometimes create lidded ducts but more expensive and time consuming.
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On Saturday 09 March 2013 13:53 imanc wrote in uk.d-i-y:

Save some money and get
http://www.bes.co.uk/products/118.asp
item: 13239
Use with a car foot pump or bike pump.
I've advise testing at low pressures when dry as a fitting flying off with 10 bar of lots of air behind it is going to break something.
1 bar left for 10-20 minutes should spot any "silly" joints like the one you forgot to do up at all or one that's gone very wrong.
Do a wet test when the system is all togther and the worst leak shoul dbe not more than a weep or a drip which you can tweak in situ.
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On 10/03/2013 08:37, Tim Watts wrote:

After my recent heating system tweak (swapped around/replaced 6 rads, and added TMVs to another two (all the changes required pipework alterations), I did a long duration wet test... I stuck a pressure valve into a rad top connection in place of a blanking plate, and stuck a couple of bar in there. Then shut off the supply and left it for a day. Made sure there was no pressure drop the following day...
--
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John.
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