12 Nov 2010
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United Kingdom
I have two number UFH 12 port manifolds supplying the required heating around the house, both manifolds having issues with the TMVs not giving constant water temp causing the heatmiser room stats to cut out on floor overheat. (don't know the manufacture of the valves only the supplier underfloorheating1)
One of the manifolds is adjacent to the boiler in a plant room the other manifold is about 20 metres away (allowing for pipe runs)
The question is do I have the inners of these manifold TMVs replaced (they have been supplied to me under warranty) or do I install either one main TMV or two TMV(s) in the plant room before the UFH manifolds giving me control of the water temp as it leaves the oil boiler
If I did this I would have the existing TMV inners removed.
I have always had good reliability from Reliance valves and wouldn't think there would be an issue with pressure drop?
Thanks for any advice
Paul C
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Thanks Crezzer
I have new valve parts that resolve the issue keeping the existing valves in the manifold kits as supplied.
To change the TMVs in the manifolds isn't easy because the existing valve bodys are different from alternatives ie, Reliance.
There has been issues with the manifold TMVs in use (hence the replacement parts) so rather than changing "like for like" I suggested divorcing the TMVs from the manifolds and installing them independently. The heating engineer who installed the system, when asked the question, said he didn't think it would work but hasn't told me why?
So here we are with this thread.
Most external TMVs have only 3 ports, so you would have to fabricate pipework to allow for Primary Flow, Primary Return, UFH flow, and UFH return.
I suggest having each TMV close to its manifold for no other reason than ease of identifying its function if you get someone (else) in who is not familiar with your system. I take it the original TMVs were not from Reliance Controls.
You will need to keep the primary flow temperature up at around 70C to generate hot water at the DHW cylinder (assumption that you have a DHW cylinder!)
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Thanks, Meldrews mate
The pipework mods, replicating what is at the manifold, would be after that manifolds zone valve that is sited in the plant room and is marked up to distinguish it from the other heating and DHW zone valves on the primary circuit.
The existing TMV(s) have no identification re; manufacturer, but it isn't reliance.

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