Trv and room thermostat

12 Jan 2012
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United Kingdom
Hi guys.. I understand the general concept of trv's and room thermostat and the fact tht not to have thermostat in same room as trv.

My question is this, is it normal for the trv's not to operate until the thermostat has kicked in. I have a baxi main Eco 30 which I have set constant (for the heating as it has timer option also). But the trv radiators don't come on. For example my room thermostat in hallway temp is set to come on when it drops below 19, current temp showing is 20 so obviously thermostat has not ordered the heating to come on yet. But what if I want to use the radiator in my bedroom which has trv fitted, can I not just put tht 1 radiator on?? Coz if I can it doesn't seem to work. Even when I adjust the knob to 5 on the trv. All seems to work when thermostat kicks in when temp drops below certain temp.

Hope tht makes sense. Any help appreciated.
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TRVs do not control the boiler. They control the flow to the rad that they are connected to.

If you want to control the boiler by the rad valves you need a CMZone System from Honeywell - and it will cost you.
So am I right in saying the radiators will only kick in when the room thermostat does. Is there anyway of just using individual radiators?? Thnx for reply.
Yes you're right. and the only way to bring the boiler on for individual rads is to :

Install the the CMZone kit like I said. :rolleyes:


turn all the rads off other than the one you want to use and then turn on the boiler normally.
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it's difficult to puzzle out what you want. But if you like one room to be warmer than the room where the wall stat is, you can reduce the output of the rad in the hall by turning its lockshield down a fraction. Lockshields should be almost closed so start with an eighth of a turn. Don't adjust a lockshield more than that in one go without waiting half an hour to gauge the effects.

In case you haven't got the idea yet, it is the room stat that turns the heating on. All the TRVs do is control the temp in individual rooms, provided that the heating is running.

The rad in the room with the wall stat, should always be adjusted so it is the last room in the house to come to temp. That will allow all the other rooms to reach their preset temp first, and stay there, controlled by the TRVs.
Thnx dan. Thts Wht I was trying to figure out. My next problem is I can't seem to get just the one radiator to come on by it's own. Like I said in my initial post the boiler is set to constant. (only has 3 options, off, timer and constant). Now I'd assume to turn on just the one radiator I would leave it on constant but this is the same option for the thermostat. So can't really figure it out.

John initially my query was to do with whether trv works in conjunction with the thermostat in order for the heating to come on. But Now I just want to use 1 radiator in the house in the bedroom without having to use the thermostat. Coz thermostat in hallway and want use radiator in bedroom. Just can't seem to figure it out. See a paragraph above.
Now I just want to use 1 radiator in the house in the bedroom without having to use the thermostat.
the room thermostat turns the heating on. That's the way it works. You can move the stat to a different room if you like.
No still nothing even with other rads off. I would have assumed tht there would be an option to turn heating on without thermostat having to be on or then again there isn't as the other part of the thermostat is wired into the boiler and overtakes tht option. :?: I dnt knw.

John thermostat is on wall in hallway wouldn't be ideal switching everywhere. Plus wouldn't tht cause an issue with the trv in the bedroom if thermostat was in there too??
I would have assumed tht there would be an option to turn heating on without thermostat having to be on
wrong. You don't want to believe it, do you?

If there is a TRV in the room with the wall stat, the TRV can be removed, or turned up to a temp higher than the wall stat setting.

John ur saying it as if I'm in denial or I'm disputing you guys. It was a mere assumption based on the fact tht my prev boiler did not ave thermostat and could operate the individual radiator. Obviously if tht isn't the case with thermostat installed then fair enough.
What you are saying is that your previous boiler was not controlled by a room thermastat? Which means the only thing telling your boiler to turn off would be the boiler stat when that reaches temperature. Which would probably be why the rad you wanted to control would get hot because it would take longer for your boiler stat to reach temperature. It is current regs that you should have a room stat fitted.
If you want it like your other house then turn all radiators off and max out the room stat with the timer on constant , that way you can turn on each idividual radiator , It's your house to do what you want with. (don't know about boiler bypass though)

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