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Heating installation query

Postby chris_on_tour2002 » Mon Dec 17, 2007 10:29 am

I am having a completely new heating system put in and am going to run all the pipework to the rads myself. my question is: can i tee off from the flow pipe along the way? i know that each rad will be tee'd into the flow and return but does it affect the efficiency if i tee of the flow to route to other areas? logic states that it should make no difference, just dont want to find that one or two radiators aren't getting any hot water!

also looking at the worcester bosch 28i junior greenstar, (which i obviously do not intend to install myself) i live in a 3-bed semi with one bathroom and 7 radiators in rooms with 8 foot ceilings. i think that this boiler should be able to cope?


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Postby htg engineer » Mon Dec 17, 2007 5:11 pm

Yes you can tee off from the flow and return pipes on the way.

Run the flow and return in 22mm pipe as far as possible, and tee into this with either 15mm or 10mm pipe.

I prefer to use 15mm but 10mm is easier to run especially long lengths.

Also try not to "mix n match" use either 15mm or 10mm not abit of both, as water will take the easiest route (least friction) so the 10mm may struggle.

Never tee a 10mm branch into 10mm pipe as it will not work, you can tee a 10mm branch into 15mm pipe.
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Postby marrtin » Mon Dec 17, 2007 8:35 pm

Oh, how I hate microbore!

Use 22mm and 15mm pipe if it's for yourself. It may be more expensive, but you will get a more easily balanced system.

15mm pipe should feed no more than two rads.

I find 22mm Hep2o (plastic) real easy to use under floorboards then just do the 15mm runs in copper.

Remember that you need the final 3 metres or so run to the boiler must be in copper.
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Postby prbaxter » Wed Jan 16, 2008 10:56 am


I have 15mm pipe under the floor and then it braches off to microbore.

If I cut the microbore under the floor and then have a 15mm pipe leading to the rad, will this still work.

The microbore is a pain when changing the rad valves as its so bendy. I plan to have 15mm pipe for most of the rads as its easier to work with and easier to replace.

Also, if I by a reducer (or the opposite to connect microbore to 15mm) then what size do I require? 8mm or 10mm?
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Postby rosebery » Wed Jan 16, 2008 1:58 pm


Are you suggesting to get under the floor, cut the microbore and convert back to 15mm again to go to the rads?

If you can get under the floor why not just ditch the microbore altogether and join 15mm to 15mm?

Seems much more straightforward to me.

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Postby chris_on_tour2002 » Wed Jan 16, 2008 3:24 pm

should be fine to change from microbore to 15mm. the reducer size depends on what size the microbore is, its probably 10mm if its feeding a radiator. but i would not use a reducer, better to cut out the microbore completely and just use a 15mm tee.
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