Underfloor heating query

[D]

Hi

This might be a naive question but I'm no expert in these systems and was wondering if any one can help.

I rent a house which has an under floor heating system which is water based. The system is set up with a Vaillant combi-boiler which supplies hot water to a circuit for the taps and a circuit for the underfloor heating. Both these circuits disappear into a small storage tank so that it works in a semi-combi style, filling the storage tank first.

In the summer we turn off the heating for the floor circuit on the boiler but the floor nearest the boiler (kitchen area) still gets v. hot from the residual heating effect of the hot water ciruit(well this is my idea of how the floor is getting hot).

This gets pretty uncomfortable when the downstairs is open plan and the average temp is +30oC (French Alps, not Sarf London). What are peoples opinions on just closing the water circuits that are feeding the underfloor heating system (there are 4 pipes going into and out of the wall below floor level, with taps on the inlets). Is this likely to cause any damage to the boiler, storage tanks or underfloor heating? Like I say I have no experience of these systems so any opinions would be gratefully received.

Cheers

D.

[Aidan]

It shouldn't. All the safety devices (safety valve, expansion vessel, thermostats, etc., ) would normally be inside the boiler casing. Isolating the heating circuits coming out of the boiler shouldn't cause any harm. However, if the heating pump is isolated you shouldn't need to shut the isolating valves; it shouldn't make any difference.

I can't be 100% certain, because the boiler might be different or it could be a peculiar installation;see below. If the problem is that the boiler's pump is still running when you think it should be off, you will wreck it by dead-heading it.

I can't imagine that. Is the small storage tank outside the boiler casing?

Is it just the doemstic hot water supply to the taps heating the floor? This is quite a common installation fault with UFH, typically pipes are run from manifolds along corridors to numerous zones. If the pipes are not properly insulated, the corridor gets excessively hot.

It may also be that the system has been incorrectly wired, or the electric controls are inadequate, so that the boiler's primary heating pump is still running (causing the floor to get hot) and the UFH is isolated at the manifolds' control valves.

There would typically be a mixing valve and an UFH secondary pump at the manifolds. The primary heating pump would be inside the boiler, circulating water from boiler to manifolds. No demand from all the UFH manifolds should turn off the boiler's primary heating pump.

I shouldn't mess about with the heating then. Put a rug down. Dry wet clothes on it.

[BigWallop]

We can but try. :-)

Tell your landlord to get it sorted.

Does the floor get hot only when you demand hot water, or does it get hot and stay hot all the time?

If the floor is only getting hot when you demand hot water to other parts of the house, then the pipework sounds as though it isn't properly insulated. You'll be using money heating the house rather than just getting hot water to the taps.

Does the small tank also get hot? If the small tank is a red or an orange colour, then it is actually a pressure vessel which keeps the system supplied properly with a head pressure of water. This shouldn't get hot, a little warm maybe, but not hot if it's being used correctly.

[Doctor Evil]

underfloor heating?

..or better still ask the landlord how the heating works.