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15mm copper pipe and 10mm microbore CH

Postby bingbing » Wed Apr 14, 2021 7:21 pm

Hi all. We are in the process of renovating our home and I have been pondering how to plumb in the rads on the ground floor as the floors are concrete. Firstly the system is a boiler only system, open vented with how water tank in airing cupboard. Up stairs there are four rads and a heated towel rail which I have plumbed with 15mm copper using standard feed and return pipes. Eventually on the ground floor we plan five rads.

I had assumed that I would 'simply' be chasing out the concrete floor at ground level and either install copper pipes (in ducts or wrapped to protect them for the concrete) or plastic to plumb the downstairs rads. But then on the internet I discovered manifolds and microbore. Running this from the ceiling and chasing into walls would be much easier. So my questions are...

1: Is it fine to have 15mm copper feed and return system for first floor rads and manifold and 10mm microbore for ground floor rads?
2: Assuming the answer is 'yes' can I put the manifolds onto the 15mm copper pipes are already installed to feed the ground floor rads or do I need to tee off the 22mm boiler feed and returns and place them on those?
3: If I go for the design above are there any percautions or design considerations I need to take into account? (I'm thinking balancing really, different flow rates??)
4: Micro bore pipes in walls concern me a little. Do I/should I install in metal conduit to add some protection or am I being paranoid?

All advice very much appreciated. Bing
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Postby aethelwulf » Sat Apr 17, 2021 8:08 am

I am not a qualified plumber. My house in which I have lived for 26 years has your type of system. I have a system boiler in the utility room installed in 1977 still working , gravity HW and 22mm feed and return mains for the CE which is obviously pumped. These are are fist floor level and there are two manifolds situated under the bedroom floors. Therefore all rad pipes and feed down the walls to the rads. The size of pipes will be determined by the heat requirement of your rads. 10mm pipe can carry 2500 KW but not for long. But the microbore is easy to manipulate with tools and is neat. Mine of course were installed by the builders and are hidden in the plaster. I have added/taken away certain ones. Best to hide them in corners . Looks a messy job to retro fit manifolds but could be done if you renovating.
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Postby ericmark » Tue Apr 20, 2021 1:52 pm

Theory the less water the boiler heats, the faster the heat reaches point of use, so Myson fan assisted radiators on micro bore should heat home faster, however it does not quite work out that way.

The whole of the central heating system is a compromise, very easy to say what you should do, but every home is different, with my first two homes the central heating worked, and as a result never really thought about it, only when I returned to live with mother, did I realise what works in one home, may not work in another.

It took two years to get her house working as it should, then she died so we sold it. But the problem was speed. With my house reaction time was not a problem, but with her house, large bay windows would heat the living room fast when the sun came out, so radiators had to stop heating room just as fast.

The more homes I have lived in, the more I see how what in one house worked A1, does not work in another, so I had mixture of pipe sizes from 32 mm to 8 mm and it worked fine, but that does not mean it will work for you.
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