Combi Boiler advise

15 Jun 2008
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United Kingdom
I am looking to change to a Combi boiler but all my radiators are fed by
8mm micro bore. As I believe these systems run at a much higher pressure will I need to change my micro bore to a larger bore pipe or
is the 8mm micro bore compatable with these type of boilers.

Advise on any compatable boilers would be greatly appriciated.
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It may work, but someone posting on here a while ago found it was not working properly and the boiler makers, Worcester, advised him that they dont expect their boilers to work properly on microbore systems.

There was insufficient flow rate and the boiler was overheating.

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Pipe bore is an important factor as is system having to be clean.

Pipe has to be of diameter and length to adequately supply water required by a radiator regardless of radiator size. A large radiator with 6 inches of 8mm pipe will work just as well as a tiny radiator on same size pipe much further away. It is all a question of quantity of water required by the radiator and pipe being able to supply this.

Regularly work on systems plumbed in 8mm microbore, connected to combi boilers without any problems.

Have been to a few new build houses fitted with combis, piped in 10mm plastic with restrictive plastic inserts at terminations. Anyone care to check inner bore size on this pipe compared to 8mm?

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