Thermostatic Rad Valves How do they work?

[darkan9el]

Thermostatic Rad Valves, how do they work?

Do they sense the room temperature and regulate the heat accordingly? or are they just a flow control ie 5 lets lots of how water through 1 lets a bit through.

I have a rad in the hall that doesn't have a TRV I understand this is required, but should I have a thermostat nearby to control the temperature or isn't one required because I have TRV's on each rad barring the hall rad?

 

[gassafeengineer]

senses room temp and forget about everything else you said its irreelevant yes it is correct im not going to bore you with technical jargon all is ok

 

[tamz]

The numbers on a TRV relate to room AIR temperature and have no relation to how hot the radiator will get. When some radiators feel cooler than others it is because it has shut off and is cooling down.
Number 3 on a valve relates to an AIR temperature of roughly 20 degC and each number up or down changes the AIR temperature by 4 degC difference each number. Number 2 is therefore around 16 degC (60 F) room AIR temperature and number 4 around 24 degC (75 deg F).

The hall rad does not have a TRV because if all other valves close down this is the only place for the water to circulate. You should have a room stat fitted in the hall which when up to temperature will switch off the boiler.

 

[D_Hailsham]

The numbers on a TRV relate to room AIR temperature and have no relation to how hot the radiator will get. When some radiators feel cooler than others it is because it has shut off and is cooling down.

A TRV is not a switch which opens when the room is cold and closes when the room has reached temperature; it is a proportional control. When the room is below temperature the TRV will be fully open. When the room reaches temperature the valve will close down just enough for the flow through the rad to maintain the required room temperature.

If a rad fitted with a TRV goes alternately hot and cold, it is a sign that the systenm is not properly balanced.

 

[tamz]

The numbers on a TRV relate to room AIR temperature and have no relation to how hot the radiator will get. When some radiators feel cooler than others it is because it has shut off and is cooling down.

A TRV is not a switch which opens when the room is cold and closes when the room has reached temperature; it is a proportional control. When the room is below temperature the TRV will be fully open. When the room reaches temperature the valve will close down just enough for the flow through the rad to maintain the required room temperature.

If a rad fitted with a TRV goes alternately hot and cold, it is a sign that the systenm is not properly balanced.

I know exactly how they work Mr Hailsham but simplified it for the sake of being easily understood.

OP have a look at this

http://heating.danfoss.com/PCMPDF/operation_princip_facelift.swf

and you may find this of interest

http://heating.danfoss.com/PCMPDF/TRV_euro.swf

 

[D_Hailsham]

I know exactly how they work Mr Hailsham but simplified it for the sake of being easily understood.

Unfortunately you simplified the explanation so much that it was misleading.

The majority of people, including the professionals, think that a TRV is like a switch which: open when the room is cold; closed when it is up to temperature. You appeared to be perpetuating this fallacy, as does the Danfoss "explanation"!

 

[ChrisHe01]

What is a Thermostatic Radiator Valve?

A thermostatic radiator valve (TRV) controls the temperature of a room by determining the flow of hot water to a radiator. Fitted to radiators on an individual basis, the valves allow you to vary temperature according to room, so if you have a south-facing room which receives a lot of sunlight, a TRV would limit the flow to that particular radiator when the rest of the house needs heating.

How Does it Work?

When a room drops below a specified temperature, a wax plug expands or contracts, controlling a pin connected to a valve. When the valve is triggered, it will open to allow warm water to flow into the radiator. When the room has reached the desired temperature, the valve will gradually close.

Valves gauge the temperature of a room using the air directly around them so it’s imperative to ensure that they are not covered by curtains or any other material. They need an uninhibited passage of air flow to allow them to effectively read the temperature of the room.

 

[Charnwood]

4 years late, but thanks anyway.

 

[CaptainRantflaps]

Remember when using a TRV.

1 = Warm
2= Hot
3 = Really Hot
4= For drying plaster or cooking eggs
5 = For melting Iron