Radiator thermostats

Spoonie_Turtle

Deleted_User said:

Spoonie_Turtle said:

Hope it's okay to ask here, as it's on topic but not actually answering the original question - is it true that the numbers correspond to actual temperatures regardless of what the heating's set to?  We have a heat pump, if that makes any difference.

I think I understand the basic premise, they turn off water flow once the room gets to the relevant temperature, but I'd assumed the numbers on the valves were relative to the temperature of the overall thermostat, not independent temperatures regardless.

TRVs (unless they're smart ones) have no idea what your thermostat is set to.

That makes so much sense I'm almost embarrassed not to have realised it before.

Alnat1 said:

They vary slightly by make and model but usually
* is 5-7C
1 is 10C
2 is 15C
3 is 20C
4 is 25C
5 is 30C

That is very helpful, thank you!

tux900

Spoonie_Turtle said:

Alnat1 said:

They vary slightly by make and model but usually
* is 5-7C
1 is 10C
2 is 15C
3 is 20C
4 is 25C
5 is 30C

That is very helpful, thank you!

Try not to get too fixated on absolute temperature settings. The temperature detected down near the floor, next to the radiator, and with hot water running through the valve etc will differ in an indeterminate way to that elsewhere in the room. You're best off measuring the room itself and tweaking the TRV up/down to adjust to suit your desired results. I suspect this is likely why the TRV heads don't carry temperature markings given how misleading they would be (but may include them in the instructions where they can at least discuss the shortcomings in TRV location when it comes to temperature measurement).

For what it's worth, my Siemens TRVs have the following mappings:

* is 8C
1 is 12C
2 is 16C
3 is 20C
4 is 24C
5 is 28C

Similar, but different, to those of Alnat1's (as they said they would). Interesting the common '3 is 20C' mapping - I wonder if that might be something of a de facto standard (hard to tell from only two samples!), or maybe just coincidence!

[Deleted User]

Drayton don't seem to want to tell me, but they say that * is 8C and 4 is 22C.

Others are more helpful - a selection:

Danfoss:


Honeywell:


Tradefix:

BUFF

Deleted_User said:

Drayton don't seem to want to tell me, but they say that * is 8C and 4 is 22C.

The instructions for a Drayton TRV4 say it is adjustable between 10C &  27C 
https://www.draytoncontrols.co.uk/sites/default/files/TRV4 (U.&I. Guide)_1.pdf

Spoonie_Turtle

tux900 said:

Spoonie_Turtle said:

Alnat1 said:

They vary slightly by make and model but usually
* is 5-7C
1 is 10C
2 is 15C
3 is 20C
4 is 25C
5 is 30C

That is very helpful, thank you!

Try not to get too fixated on absolute temperature settings. The temperature detected down near the floor, next to the radiator, and with hot water running through the valve etc will differ in an indeterminate way to that elsewhere in the room. You're best off measuring the room itself and tweaking the TRV up/down to adjust to suit your desired results. I suspect this is likely why the TRV heads don't carry temperature markings given how misleading they would be (but may include them in the instructions where they can at least discuss the shortcomings in TRV location when it comes to temperature measurement).
 …

Thanks, yeah that all sounds sensible.  I had no idea the temperature range at all though so having even a vague reference range is helpful.  I think there's only one room that could have them turned down (with the overall thermostat set to 18℃, rooms being too warm isn't a routine worry!), but useful to understand how they work.

TheBanker

I've just had thermostatic valves fitted to most of the radiators that didn't have them. I work at home most days so I am sure I will save gas by being able to turn off the heat to rooms that aren't being used. It cost me approx £150 for a plumber to supply and fit four valves. I am hopeful that I will save that in fuel costs quite quickly. I'd booked this work before the Price Guarantee was announced; the savings will obviously be less under the lower prices, but still worth having I think.

I am not alone - the plumber said he's been fitting lots of TRVs recently.