Thermostats

[eddieriff]

I have Thermo controls on my radiators but they are there for appearance purposes only, they're useless.

I do not have room or hallway thermos. What I do have however, is a thermo control on my gas boiler. Is it best to have the thermo set on low.....then I assume the gas will ignite more often or should I have it set on high and assume that the gas will ignite not so often. I'm obviously trying to use as little gas as possible, aren't we all, without freezing my wife to nagging point......oh wait!

 

[ALEC1]

Yes TRVs are useless, and wasteful compared to modern controls which automatically vary the boiler and flow temperature according to how much heat is needed to maintain a temperature..

The problem with TRVs is that they don't tell the boiler anything...

Varying the flow temperature as you do should save energy...especially on a condensing boiler

 

[45yearsagasman]

You need to give a better description of your system, eg boiler and other controls. Your assumptions are incorrect.

 

[eddieriff]

You need to give a better description of your system, eg boiler and other controls. Your assumptions are incorrect.

It's quite old, no other controls other than a timer.

 

[JBPHS]

Hi eddieriff

Thermostat on boiler controls water temperature in heat emitters (i.e. radiators). These control when and how (if the burner modulates) the burner operates. These are usually irrelevant if an outside temperature sensor is connected to the boiler.

Room thermostat switches on heating (if other controls are calling for heating) if air temperature around that thermostat is below the temperature it is set at. These control the heating function on the boiler.

Thermostatic Radiator Valves (TRV's) control the flow of heating water into the radiator (if the heating is on), depending on the air temperature around the thermostatic radiator valve head. These work best usually when the heads are positioned horizontally (as opposed to the typical upright position). They also work best when set correctly (i.e. start with position 3 if 5 is the maximum and then increase or decrease by 1/2 an increment after the heating has been running for an hour or so if the room still feels cold or too hot). As said earlier, these do not control the boiler.

In your case, the timer is doing the same as the room thermostat, but using time to control the heating and not the air temperature. Your system would benefit with a room thermostat wired in series (after the programmer and before the boiler).

Hope that helps.

 

[mogget]

The problem with TRVs is that they don't tell the boiler anything...

Actually they do, in a way. As the TRVs shut down the return temperature to the boiler rises and it 'knows' (through the boiler thermostat) that it needs to burn less gas to keep the water hot.

Or if you have a modulating pump, flow through the boiler reduces and the boiler modulates down to keep the flow temperature stable.

There doesn't have to be an electrical connection for information to be transmitted.

OP, the problem with TRV-only (no room stat) systems is that once the room / house reaches temperature, the boiler will burn gas to counter heat loss from the (unnecessarily) hot pipes.

Other problems with TRV's is that they are hard to set accurately, and measure the temperature at a point near the floor.

 

[eddieriff]

Thanks for you replies chaps (or chapessess), much obliged.

 

[JohnD]

if you mean your TRVs have all become faulty, and they have all failed fully open even when you turn the knob down to minimum:

how old are they, and what make?

 

[eddieriff]

if you mean your TRVs have all become faulty, and they have all failed fully open even when you turn the knob down to minimum:

how old are they, and what make?

Over ten years old and Myson.

 

[JohnD]

you'd better save up for some new ones, and change them once winter's over.