How to zone underfloor heating

Our re-furb is grinding ever onwards approaching completion asymptotically (i.e. never getting there!).

We have wet under floor heating in one part, and conventional radiators elsewhere, both heated by a Grant oil fired boiler. Should we have a three zone controller, for a/ Hot water, b/ Radiators and c/ the three under floor areas (which each have a thermostat. or should the under floor and the radiators be on the same output from the controller?

AWEM

Reply to
Andrew Mawson
Loading thread data ...

3 way controller. the response times of an in screed system is RADICALLY different from the radiator system.

If you want to go two way couple the hot water to e.g the UFH system timer wise.

Fit three master stats anyway and run as three zones. As well as zone/radiator stats.

The tank stat can be the sole HW stat

Reply to
The Natural Philosopher

I'd have them on the same output as the CH, but have a separate stat for each area. Gets more complicated with the piping, but fairly straightforward and common. You can then set the floor for, say, 15 degrees, and the CH for 20.

Reply to
A.Lee

NO. never on the same timer. Screed floors take HOURS to warm fully, and you may want more intelligence on the thermostat to minimise overshoot.

Reply to
The Natural Philosopher

The number of zones in a building depends on the occupation pattern. Some areas will be constantly occupied, others perhaps infrequently so. So these areas can be divided apart and independently controlled. Also if some areas are significantly warmer than others.

So fuel savings can be made.

This has been done in large commercial buildings for years. It only becomes viable in domestic houses as fuel prices rise. After all you can turn radiators off manually. However even now, you'd need a big house to make it worth while.

The alternative method is for each zone to have it's own heat source/ boiler which in some cases works out cheaper.

Reply to
harry

With regard to underfloor heating. This allows boilers to run efficiently because of low water temperatures.

However, it can't be turned on and off daily as it has high thermal inertia. Probably going to take a couple of days to warm up from cold. It needs to be installed in a well insulated building. Sometimes the UF heating is used as "background heat" and topped up from other sources as required.

Reply to
harry

Our situation is the same: UFH downstairs and radiators upstairs (plus hot water). The radiators and hot water are controlled by a conventional timeswitch, but not the UFH: as far as the boiler is concerned that's 'permanently on'.

The UFH zones (we have 6) each have their own UFH thermostats; they switch between 17C and 21C according to the time of day, but again they never turn the system 'off'. The UFH can, and does, come on in the middle of the night in order to maintain the 17C minimum.

Richard.

formatting link

Reply to
Richard Russell

Only if the boiler isn't required to feed anything else! As our boiler feeds radiators and a hot water cylinder in addition to the UFH it runs at a fairly high flow temperature of 65C. The UFH manifold arrangement incorporates a thermostatic mixer valve to reduce the temperature to 45C for that circuit.

Richard.

formatting link

Reply to
Richard Russell

Unless you actually want to turn the UFH off via a programmer then there is no need to have a 3 zone controller. The programmable stats in your 3 UFH zones should do their job and these should have a permanent live.

Reply to
ARW

That is a reasonably valid point EXCEPT that most UFH zone valves controlled by stats are NOT master stats as such and do NOT stop the pump running. Not the UFH pump: not the boiler pump.

They are analagous to TRVs in radiators.

Now you COULD fit motorised valves, at which point the points you make become valid, because you can wire OR the outputs and use them to control the pumps. But that is not the way most installations work.

In the end you need a time because you don't want to heat when you don't need to. That might be in the thermostats or it might not, but its still needed.

What all this means is that UFH needs to be thought through carefully and 'conventional thinking' does not apply.

Reply to
The Natural Philosopher

Take care with what UFH system you have ... many have a temp that is much less than rads and if you run them at rad temp they will fail.

That is why many are used with Thermal store with 2 heat exchangers ....

1 for DHW the other at bottom of store for UFH supply
Reply to
Rick Hughes

HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.