Close-coupled Tees (Underfloor heating)

[Andy StopfordParticipant @andystopford50521]

Someone has asked me to connect some pipework in a central heating system with a new underfloor heating (UFH) system on the ground floor, and radiators on the first floor (they didn’t fancy doing the soldering).

There is no plan for exactly how to connect the two systems, and much talk on Youtube etc. about using a close coupled tee to hydraulically isolate them. Much of the talk expresses conflicting opinions, and possible total nonsense, as one might expect.

Does anyone know how this is supposed to be done – where the tee goes, is the branch to the UFH supposed to be in series with the radiators or parallel, etc.?

[Andrew CrowParticipant @andrewcrow91475]

Hi Andy, I have never dealt with underfloor heating but, I would have thought it should be treated as another radiator in the system and therefore in parallel to all other radiators in the system otherwise all the other radiators would be a little cooler. Just a thought!

Andy

[JasonBModerator @jasonb]

Jobs I have been involved with all the UFH has had a separate pump and mainifold to the pipe loops. Motoirised valves isolate and open when either upstairs/existing radiator stats call for it or the UFH stats.

Several were adding UFH to just one room and they plumbers never just added it to the radiator loop.

[Andy StopfordParticipant @andystopford50521]

This has a manifold with its own pump,  and a mixing valve which effectively controls the UFH temperature which has to be lower than the temp in the primary (radiator) circuit.

So you have two circuits joined together,  and the problem is stopping the pumps either fighting each other,  or working together to double the pressure (which apparently can cause pump failure). To prevent this,  two of the pipes are bridged by a short pipe (the close coupled tee), but the question is which two pipes,  and where?

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