Extra underfloor heating wiring

[Norv]

Wired a heating system using 2 zone valves & 2 stats(one for upstairs & one for down), boiler is a condensing boiler.

Customer has now decided to have underfloor heating in the kitchen & a manifold has been fitted. Ive put a thermostat cable from the wiring centre for a room stat in the kitchen. On the manifold is a pipe stat. Does this have to be wired aswell ? What does this do ?

Also, if the stats in the other part of the house are calling for heat & the kitchen stat isnt, the underfloor pump on the manifold would run with its zone valve closed, would this be ok?
Thanks

 

[PrinceofDarkness]

Norv: So you have two separate heating zones and want to add another - in the the form of UFH? Do you also have DHW on this system - which would make for four programmer channels?

How many circuits are connected to this UFH manifold - and do they all serve the same area?



Lucia.

 

[Norv]

Yes two seperate heating zones & want to add u/floor htg zone.

DHW is controlled by the boiler & programmer built into the boiler. If heating is turned on at the boiler then all heating zones will be live.

There is one circuit on the manifold covering the kitchen only.

 

[PrinceofDarkness]

As it's only one UFH circuit for only one room, then it might just as well have been incorporated into the general ground floor zone without the unnecesary manifold.

And...... No, of course you can't wire the UFH pump to run without the valve being open!


Lucia.

 

[Norv]

Just thought If I wire the UFH pump between the SW L of the stat & the zone valve then the pump will only run if the stat calls for heat & the valve will be open

 

[flameport]

The pump/manifold IS required even with one zone, otherwise the UFH will operate at the temperature of the other radiators, which will be far too hot.

The thermostat on the manifold is possibly there to indicate the temperature is too high, so this must be used. However it could be there for some other reason - the instructions for the manifold will have details.

If the pump is running with valves closed, it won't last very long, and the system is wired incorrectly.

 

[PrinceofDarkness]

And so it should, if you do it that way. But I still don't see the need for a manifold for such a simple system.

A UFH manifold generally consists of mini-actuators to control the various coils of a system over a number of zones. This is surely not the case here?

Lucia.

 

[Norv]

The manifold wasnt my decision. The plumber installed it. Im just wiring it & it will be wired correctly.

Cheers for the help.

 

[PrinceofDarkness]

Oh well, you can only play the hand that you're dealt.....


The important thing is the thermostatic control over the UFH. The manifold does nothing but distribute the heat to the various coils via its actuators.



Lucia.

 

[SUNRAY]

Oh well, you can only play the hand that you're dealt.....


The important thing is the thermostatic control over the UFH. The manifold does nothing but distribute the heat to the various coils via its actuators.
Lucia.

Thats if it has actuators fitted. If it does then you may not need the extra pump unless the UFH line(s) are very thin

Just thought If I wire the UFH pump between the SW L of the stat & the zone valve then the pump will only run if the stat calls for heat & the valve will be open

This 'extra' pumped and valved circuit should not be on the load side of an existing Zone valve, it should be direct off the boiler (or boiler header). The new UFH circuits control thermostats (note plural! space and manifold) should then be able to enable the boiler.

 

[Norv]

This 'extra' pumped and valved circuit should not be on the load side of an existing Zone valve, it should be direct off the boiler (or boiler header). The new UFH circuits control thermostats (note plural! space and manifold) should then be able to enable the boiler.

Yes, the UFH is not on the load side of any other valve. Its direct off the boiler.

 

[SUNRAY]

This 'extra' pumped and valved circuit should not be on the load side of an existing Zone valve, it should be direct off the boiler (or boiler header). The new UFH circuits control thermostats (note plural! space and manifold) should then be able to enable the boiler.

Yes, the UFH is not on the load side of any other valve. Its direct off the boiler.

So to confirm, you have:-
Kitchen room stat.
UFH manifold stat.
UFH pump.
UFH valve and actuator.
Does the UFH valve have a switch to indicate that its open?

There are several ways of wiring this, for a start the 2 stats are to be wired is series so the space temp and the manifold temp must be below their set points to operate the UFH. Ideally the stats will open the valve and its 'open' switch starts the pump and the boiler, this will need 2 contacts so a relay will be required. You could wire the pump off the stats too and use the 'open' switch to operate the boiler but this poses the risk of running the pump when the valve fails to open.

If there is no 'open' switch then the stats will need to operate the valve, pump and a relay and the relay contact will start the boiler.

Hope that makes sense to you.

Ray

 

[holmslaw]

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[SUNRAY]

The only useful advice has come from flameport.

If UFH pipework is connected to standard radiator pipework there's has to be a means of limiting the water temperature to below 50C. It is therefore impractical to connect the two together, the pipe stat is there to control a valve that will cut off the flow if it gets above 50c.

The system is never going to work because the water temp will always be above 50C.

I have sorted several UFH systems to get them working after the heating engineer gave up. Using the method described they worked.

May I ask why you reckon it will not?

 

[holmslaw]

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