Two way valve - underfloor heating

[scottydog]

Hi,
I need to wire in a two way valve to control underfloor heating added to my gas wet central heating. Valve is to be controlled by a standard thermostat.
Two way valve is a Pegler TerrierTZV22 - can anyone advise how the valve is wired to the thermostat - will the valve just require a switched (via thermo) supply and a common neutral, or do I need to wire in the grey and orange cables too?
Thanks.

 

[giblets]

Shouldn't it be a mixing valve on u/f heating or have I lost the plot.

 

[scottydog]

Don't believe so - it's effectively like adding an additional radiator - well the system I have installed is!.
The two way valve is effectively just like the on-off valve on a rad, the difference being it is motorised.

 

[giblets]

But will the temperature of the floor not get up to the temperature of the radiators then? Be a bit warm underfoot surely.

 

[clf-gas]

Don't believe so - it's effectively like adding an additional radiator - well the system I have installed is!.
The two way valve is effectively just like the on-off valve on a rad, the difference being it is motorised.

on you go big fella

 

[Gasguru]

Underfloor timeclock switched live feed to U/F room stat (and neutral). Then stat switched live to motorised valve motor AND U/F pump.

Then the U/F motorised valve switch feeds live to the boiler and main pump (unless controlled by the boiler) as with the other zone valves.

This is assuming its a standard U/F system ie it has it's own pump and thermostatic mixing valve (injection system) and an auto bypass valve is installed (and setup).

 

[scottydog]

Guys,
thanks for the feedback so far...the u/f loop is just connected like an additional radiator. The valve is on the flow and will be switched via a thermostat in the room served by the u/f heating - the stat is to control the temperature in this room only. I understood that it was "just" a case of switching the live to the valve to open it and then when set temp was reached, stst would cut supply, closing valve.
Or have I got something horribly wrong??????

 

[giblets]

Or have I got something horribly wrong??????

I think you may have.

Normally u/f heating runs at a far lower temperature than the ordinary radiator circuits hence the mixing valve, own pump, etc. As I said, your floor is going to get very hot based on the way I think you've installed it.

 

[Gasguru]

Ignore my previous posting then...it appears you are using a kit such as the Polyplumb ZRU. What do the manufacturers instruction say...what make/model is it.

 

[Doctor Drivel]

Guys,
thanks for the feedback so far...the u/f loop is just connected like an additional radiator. The valve is on the flow and will be switched via a thermostat in the room served by the u/f heating - the stat is to control the temperature in this room only. I understood that it was "just" a case of switching the live to the valve to open it and then when set temp was reached, stst would cut supply, closing valve.
Or have I got something horribly wrong??????

Having the floor too hot will destroy the plastic UFH pipes. The floor will be too hot. You need to find out how these things work. The UFH zone needs its own pump and blending valve to take the temperature down to 55C maximum

DO NOT do it as you are proposing.

 

[ChrisR]

We often see UFH connected like a normal rad, but with a thermostat on the return (from the ufh) pipe so a valve shuts off the flow, and the pipe just cools down from 80 or whatever, until the stat opens the valve again.
OR
a thermally operated valve (a bit like a trv but sensing water temp) on the return, so it stabilises to a nearly-shut position, with flow through the ufh so slow that it cools right down to give the average temp somewhere about right.

Neither system works very well. The first makes the floor get v hot, then it cools to warm, then goes hot, etc.
The second gives you one end of the ufh loop at say 80, and the end with the valve at say 35 - 40. One symptom that gives is a very uneven temperature across the floor.

There's no shortage of half-cock schemes around, with a pump added, say which are little better. And the whole thing is often the wrong side of the CH zone valve so you can't control it separately!

Visit a few mfrs site - polypipe, wirsbo, nu-heat etc, to see their systems.

 

[croydoncorgi]

The second gives you one end of the ufh loop at say 80, and the end with the valve at say 35 - 40. One symptom that gives is a very uneven temperature across the floor.

Disagree.

IF the UFH system has it's own pump (usually between the blending valve and the manifold Flow-side actuator valves), the flow through each active loop (about 2litres/minute) SHOULD be sufficient to ensure that the temperature drop in the loop is not enough to be a problem. And I can't see why you think that the flow end of a loop could ever be as hot as 80C degrees - the purpose of the blender and dedicated pump is to ensure this does NOT happen!

I'd agree that the simpler types of UFH layout are often iffy, however.