Combi Boiler and TRV's

rl1

Any experts out that who can resolve a difference of opinion. We have recently had a combi boiler and new radiators fitted and the plumber has put TRV's on all the radiators including the one in the hallway where the thermostat is situated.

We were under the impression that the room with the stat should not have a TRV. Does anyone know who is right?

primrosey

Hi my corgi hubby says your quite right the room with the stat shouldn't have a TRV.

bockster

to the best of my knowledge, definitely shouldn't be a trv in room with room stat. depending on both stat settings, room could warm up, trv closes, room stat doesn't see any more increase in temp, so boiler will just keep running. if all rads have trv,s then hope there is a bypass in the system, either built in the boiler or built in to the pipework.

CLAPTON

why do you need a room thermostat if all rooms have a TRV?

rl1

CLAPTON wrote: »

why do you need a room thermostat if all rooms have a TRV?

Well I don't know much about this sort of thing but I thought it was the room stat that told the boiler whether to come on or not.

DNK

CLAPTON wrote: »

why do you need a room thermostat if all rooms have a TRV?

I think that's the question to ask the plumber!

Incisor

CLAPTON wrote: »

why do you need a room thermostat if all rooms have a TRV?

[If all the other rooms have TRVs, the room stat should ideally be in the slowest room to heat up...]. You need the room stat to turn the boiler off so that it is not running at low efficiency on short start stop cycles.

derrick

If using TRVs you do not need a room stat, if you have the stat and that room gets satisfied the whole house shuts down defeating the TRVs in the other rooms.

Also unless the boiler has a by pass that operates when/if all TRVs close, there should be one radiator left without a TRV, usually the bathroom one, otherwise the pump will still run and could seize as there will be nowhere to push the water.

In this case without the room stat the boiler stat will control the water temperature in the system, the more rads closed via TRVs the less water that will be heated until TRVs start to open.

Incisor

derrick wrote: »

If using TRVs you do not need a room stat, if you have the stat and that room gets satisfied the whole house shuts down defeating the TRVs in the other rooms.

Hence have the one room without a stat as the slowest to heat up. Systems done this way work a treat, provided the room stat is wired correctly with the anticipator heater element wired in, and they use less gas too.

Also unless the boiler has a by pass that operates when/if all TRVs close, there should be one radiator left without a TRV, usually the bathroom one, otherwise the pump will still run and could seize as there will be nowhere to push the water.

There should be another bypass anyway, because the non TRV radiator could be shut down manually. I doubt the pump will seize, but the boiler could start overheating and bubbling violently

In this case without the room stat the boiler stat will control the water temperature in the system, the more rads closed via TRVs the less water that will be heated until TRVs start to open.

But then the boiler continues to heat the one room without a TRV, often needlessly. The thermostat allows the boiler to shut down.

rl1

I so confused now

derrick

Incisor wrote: »

Hence have the one room without a stat as the slowest to heat up. Systems done this way work a treat, provided the room stat is wired correctly with the anticipator heater element wired in, and they use less gas too.

Not the way to do it , if using TRVs, room stat not required as the reason for TRVs is to control individual rooms, a room stat with all the best will in the world will at some time close down the system defeating the object of TRVs!


There should be another bypass anyway, because the non TRV radiator could be shut down manually. I doubt the pump will seize, but the boiler could start overheating and bubbling violently

Most modern day boilers do have bypasses, but some don't and the way round it is to use one rad without a TRV,( you would normally put lockshield valves on both ends of non TRV rad to overcome that "problem"), as said the bathroom one as that is the one were you get undressed and in and out of hot water,(shower/bath). The boiler will not "overheating and bubbling violently" as it will have it's own control stat.


But then the boiler continues to heat the one room without a TRV, often needlessly.
Exactly the same as you suggest above re the "non TRV radiator"

The thermostat allows the boiler to shut down.
The idea, as for a room stat, is to use the coldest room, usually the bathroom, but could be the hallway. that is the way a heating engineer would do it, not sure about a plumber!

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