Thermostat and TRVs

[deuce22]

Hi.

Can someone please tell me if I need a main Thermostat if I have TRVs fitted to each radiator in the house.

Thanks.

 

[Armo74]

You do need a room stat otherwise there is no communication with the boiler to shut down when the desired room temperature has been achieved.But the room with the room stat should not have a TRV. The TRV's will just control the other room temperatures. Besides it is current reg's anyway.

 

[deuce22]

Thanks Armo74.

A friend who has only been in the trade for a couple of years has been doing all the work for me, but I do like to check that everything is being done correctly.

Cheers.

 

[Agile]

In many cases somebody new is more knowledgeable than some of the old buffers who dont keep up to date.

Many of these regulations change from time to time.

For example ALL rads should now have a TRV ( except in the room with the stat ).

But an auto bypass valve is needed whereas in the past installers often used a bathroom rad with no TRV.

Tony

 

[namsag]

Agile is one of those that cant keep up with regs or more likely cannot understand them.

It all depends what boiler/system you have wether you can have trvs on all the rads without having a room stat .

So the first question anyone should ask before jumping in feet first is what boiler do you have .

 

[deuce22]

Hi namsag.

The boiler is a Ravenheat 42kw A Rated Condensing Combi Boiler and there are TRVs on every rad in the property.

I agree that in some cases new tradesmen are more keen to learn, so the sometimes know more than more experienced guy's, but the reason I'm checking is that a different Plumber said I don't need one.

I have a bit of an idea of how it all works with TRVs, but not 100%.

The way he explained it to me was, if the main thermostat is set to 17 degrees, but you have the living room TRV set to maximum as soon as the main stat turns off the boiler it will shut down the whole system. Therefore you may never get the desired temperature in the living room.

The way to overcome this is to set the main stat to maximum and then adjust each individual TRV. Instead of doing this, don't use a main stat, turn the boiler to the temperature that will exceed the maximum TRV and let them shut down the flow from the boiler.

I don't know if this is correct, but seems plausible. My only concern was, does the boiler itself have an internal stat and if so will it keep heating water in the pipes (not rads) to keep it to the temperature that the boiler has been set.

I don't care what I have to do, but I want the system working properly.

Thanks.

 

[Boilerman2]

That's why the Room Thermostat should be fitted in the room you want the warmest, i.e Sitting Room/Lounge, the other rooms such as bedrooms etc are controlled at a lower temperature by TRV's
Simples!

AND YES a Room stat or other electrical interlock is a requirement of Building regs part L1.

 

[Dan Robinson]

The way he explained it to me was, if the main thermostat is set to 17 degrees, but you have the living room TRV set to maximum as soon as the main stat turns off the boiler it will shut down the whole system. Therefore you may never get the desired temperature in the living room.

He's an idiot.

 

[namsag]

Boilerman if the BIG YES is a dig at me ,who said an interlock was not required .
The question was about a roomstat.

Thats why i asked the OP what boiler he had because anyone who knows the regs properly knows that some boilers do not require a ROOMSTAT to achieve the interlock and can be fully TRV`d.

Deuce your boiler does not have a flow switch built into it so requires one rad to be left without a trv and this must be in the room where the thermostat is.

Traditionally this was the hall but in recent times this has now become the lounge as people have moved away from having an additional fire in that room which would have affected the thermostat.
Kitchens should not have thermostat fitted in them either

 

[Boilerman2]

Actually Namsag, the BIGYES was directed at the OP