Location of thermostat in mixed UFH/TRV system

[Richard Russell]

The (new build) house we have just bought has underfloor heating downstairs and a conventional TRV/thermostat arrangement upstairs; I guess this setup is quite common. However, the thermostat (and the uncontrolled radiator) are on the galleried landing, which receives a significant amount of heat from the UFH in the hall below. Therefore there is a tendency for the bedrooms to go cold when the UFH is running, unless the thermostat is turned up.

Is this a sensible arrangement? I would have thought the thermostat and uncontrolled radiator ought to be in a zone isolated from the influence of the UFH.

Richard.

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[calums]

Russel I am no heating expert, but I would have put the uncontrolled radiator in the bathroom (perhaps as a towel rail). I doubt the landing is being affected too much by the downstairs UFH. I am assuming that each zone downstairs has its own room stat? Is there one pump for the whole system, or is the top and bottom controlled by a pump each (ie does the UFH manifold have a pump attached to it?). To sort your problem without too much work I would be tempted to restrict the flow to the radiator in the landing by screwing one valve partially down, but making sure there is still adequite flow so as not to risk any damage to the system. Trial and error over a day should get a good result. By the way, it is quite normal to have the stat near the uncontrolled radiator since the last thing you want is the TRV kicking in before the controlling stat. Good luck Calum Sabey NewArk Traditional Kitchens

[The Natural Philosopher]

Yup.

I had a similar problem. You should install a separate stat for the UFH (or the rads) as you say 'when the UFH is running' which implies its separately pumped and switched.

A radio stat is ideal.

My UFH typically has a 4-6 hour lag between coming on, and getting to proper temperature, so you need a split zone and a different timer anyway.

[Richard Russell]

The UFH already has a "separate stat" (six of them in fact, one for each zone); it's completely independent of the upstairs heating (apart from the boiler!), having its own pump and zone valve. The influence of the UFH on the rads is purely because heat from the hall is affecting the thermostat, which is mounted on the galleried landing near the top of the stairs.

The UFH roomstats are all battery powered (though not wireless) so that's already six sets of batteries to change every so often, and six clocks to adjust twice a year! Adding yet another battery-powered device isn't my definition of "ideal".

I'm very tempted to move the thermostat into the upstairs room which takes the longest to heat up (and to make that room's rad the uncontrolled one). That way all the other rooms should have reached their set temperature, under control of the TRVs, before the thermostat switches off the flow.

Richard.

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[The Natural Philosopher]

OK.. thats fair enough..

I said stat, not timer..surely you have a timer for the upstairs zone? just take the stat from where it is and put it somewhere else.

Sounds reasonable. I must say stats and TRVs don't go together very well.

I have an odd system here. No upstairs stats to control pump at all. TRVS, and thermostats on fan blown heaters. The pump runs all the time.

What you MIGHT do is take a bathroom and simply use that as a bypass..if its a very small room and it gets too hot, open the window..and forget stats altogether.

We leave the upstairs off entirely most of the time,. just hitting the 'boost' button for an hours worth of steamy bathrooms when required, or just before going to bed - apart from ultra cold weather.

[Richard Russell]

I know. It was the batteries (in a wireless stat) I was complaining about. Everything these days seems to need batteries. Personally I'd prefer everything to be wired and mains powered (with a rechargeable battery or supercap to hold settings through a power cut).

Bog standard water/heating timer next to the boiler. The only options are off/continuous/once/twice although I could presumably replace it with a more sophisticated model if necessary.

It's the normal arrangement, though, isn't it? Admittedly it does seem a bit penny-pinching to fit a multi-zone multi-stat UFH system downstairs but a basic stat/TRV system upstairs.

Richard.

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