Question about converting CH pipework - 8mm to 10mm

[Simon Hawthorne]

Hi there

My CH system uses 8mm pipe - and all the rads use yorkshire valves - where both feed and return pipes go in at the same side of the rad. I want to fit TRVs - and maybe change all my rads, without ripping out all the pipework.

Can I:

1 Fit new rads 2 Use some sort of 8mm>10mm adapter on the pipework 3 The use standard 10mm TRVs

I am a complete novice, and in the process of planning what I'm going to do with the system.

Any help appreciated.

Kind regards

Simon

[Andy Hall]

Yes, but you may not to be able to increase the size. If the boiler is a conventional 82degree flow, 70degree return, then over typical distances of a few metres from a main pipe or manifold, 8mm pipe will only support a flow able to deliver about 1500W. If it's a condensing boiler, you could have temperatures of 70 and 50 degrees, but the radiators are derated relative to their output at

82/70.

You can work out the situation by looking at manufacturer data sheets for the radiators and looking at the deratings to 89% and 60% for each scenario.

Yes you can. I used 15mm TRVs on the radiators and adaptors from

8mm female to a 15mm tail that go into theTRVs. This gives a neat solution.

For your situation, you could take one length of 8mm pipe behind the radiator to achieve a neat job.

Pipe benders (a hand tool) for 8mm tube are available very cheaply.

.andy

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[Simon Hawthorne]

Thanks for all this Andy. I was going to change the boiler - so had a few quotes (new condensing boiler, new rads & pipework, tank etc) - varied between £9k and £13k.

Just looking to sort out the rads for now - don't need any more power, but just want to control the power I have. Planning on concentrating on drafts and insulation for now (and I have lots of drafts and almost no loft insulation).

Regards

Si