Plumbing Underflorr Heating Manifolds

27 Nov 2013
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United Kingdom

I have had underfloor heating installed in an extension which is going to be run off its own combi boiler with controllable heating output temperature.
I have had installed 2 manifolds (one for upstairs and one for downstairs) and all pipes installed. There is just one zone downstairs and 2 zones upstairs (thermostat downstairs and 2 thermostats upstairs in 2 rooms). The upstairs manifold is fitted with actuators to zone the upstairs manifold. There are no radiators.


The underfloor company advise no actuators needed downstairs as its one valve and the pump on the manifolds will restrict supply (i.e. if upstairs calls for heating then the manfifold pump downstairs will stop the supply entering downstairs. My plumber has advised he wants to fit auto bypass valve for as good practice albeit underfloor company did not think this was needed...

Do we need to consider anything else? Just surprised at the view that the manifold pump will control supply.

Any views welcomed.
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If you have only two port motor valves then you need an auto bypass valves.

Why do you seem reluctant to have one?

Don't you trust your plumber?

you will probably get heat bleed through from the boiler pump due to having no control on the downstairs manifold.
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Thanks. I trust my plumber. He is the one questioning why its not detailed on the plan from the underfloor company. He hasn't done many of these and was expressing a view we should do an auto bypass and should have a 2 port motor value downstairs to stop heat bleed.
However I thought I would check on the forum as the underfloor co suggested the heat bleed would be minimal. Which made me wonder if the manifold pump had some sort of shut off valve integrated?

Thanks for the advice here!!
Just how important the motor valve downstairs is would not be know in advance.

My view is that one should be fitted. Not having one might complicate the wiring for controlling the boiler.

Also an auto bypass should be fitted in my view too!


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