How does a microbore manifold work?

17 Oct 2005
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United Kingdom

There seem to be lots of discussion on microbore, but I can't seem to find the relevant one. So apology in advance if the question is already discussed.

I have a 8mm microbore system and want to add another rad to the system. I can see there are 2 manifolds, one at each end of the house and are joined by a 22mm flow and return. Looking down at the manifold I can see that the 22mm flow enters the left side and the 22mm return coming out of the right side. The manifold has many 8mm connection points, some are used and some are not. Is there a flow and a return to the 8mm connection points i.e. can I connect the rad to any of these 8mm points on the manifold?

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There will be a flow manifold and a similar but hydraulically separate return manifold, close by, attached or otherwise. Add a pipe to each. Was that the question?!
Sounds like you have a "Wednesbury" manifold which has a flow and return manifold in one unit. Half way along the 22mm body is an internal stop, so you have your two manifolds (flow and return) in one unit, with an equal number of 8mm connections on each side of the internal stop.

You should be able to confirm this by feeling which pipes get hot first when the heating comes on. For your new rads, just use the unused connections, one from each half of the manifold. Partially drain system first.
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Chrishutt, you are spot on. The 8mm pipes on the flow side do seem to get hot before those on the return side. Many thanks for the info. :D

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