extending central heating system

15 Oct 2006
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United Kingdom
I am wanting to extend the existing CH system to include 2 radiators being installed in an extension. The extension is accessed off a living area which currently has 2 radiators. Can I use a 22mm x 10mm speedfit manifold to split the flow pipe into 4, and then another to combine the 4 returns?
Also, if the existing flow and return is 15mm can I fit a reducing tee to increase the 15mm to 22mm and then include the manifold, or does the changes in diameters cause further problems?

Thanks in advance for any advice
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You have not made it clear what size the pipe currently feeding the existing rads is.

As a rule of thumb you cannot feed more than 3-4 kW with 15 mm pipe in a standard 22/15 mm system without some heating loss.

It does depend on pipe run distances to a considerable degree.

Thanks Tony,

The existing pipe is 22mm copper. If I change to the 4way manifold, the longest run would be approx 4 metres.


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