Radiator cold

[TJ1]

I have 2 radiators in my sitting room, 1 single and 1 double, one at either end. The double which is furthest away from the boiler works fine. Presently both are set at 3 on their thermostats. The one nearest the boiler (the single one) is cold and doesn’t heat up until on 4 on the thermostat.
There doesn’t appear to be any air in the system at least not in that radiator. All the others work fine. Any ideas what the problem is please?
Thanks in advance.

 

[MeldrewsMate]

Does the larger radiator heat up the room? (of course it does)
TRVs respond to room temperature, as the room rises in temperature so the TRV restricts water flow to the rad. Thus the smaller TRV, being warmed by the heat from the larger rad, shuts off water to the smaller rad.
There's nothing to worry about. As the outside temperature drops you may find that both rads get warm/hot. That's the TRVs doing their jobs.

To test it, turn the large rad's TRV down to, say, 1.
WAIT half an hour.
Does your smaller rad (on setting 3) warm up now?

MM

 

[TJ1]

Thanks MeldrewsMate, that makes sense, I did wonder.

 

[dilalio]

From cold, they should both get fully hot until room reaches temp and one outs the other (as mm above). Also worth undoing the TRV heads and manipulating the pins up and down making sure they’re free to spring back up after depressing - this is worth doing with all TRV pins once a year (say just at beginning of heating season).

 

[TJ1]

Thanks dilalio,both radiators heated up this morning. We usually leave the radiators on full on the TRV’s to keep them open but it won’t hurt to give them all a go.