Radiators red hot but give off little heat

[ericmark]

1) Modern gas boilers can modulate (turn down output) if the return water gets too hot, so balancing is important or boiler can turn down output too early.
2) The radiator TRV can be wide open, but if the boiler is not running room will not get warm.

So the ideal is each TRV tells a central hub when it needs hot water, and really no need for a wall thermostat. But that costs, we we try doing it on the cheap, so we are told do not put a TRV on the radiator in the room with the wall thermostat, and the room with wall thermostat should be in a ground floor room, normally kept cool, with no alternative heating (including sun through the windows) and no outside doors, don't know your house, but no such room in any of the homes I have had with wet central heating, so we look at a compromise or near enough engineering.

So all rooms with TRV's and maybe more than one room with the wall thermostat. No two homes are the same, so you need to consider your own home.

Mine living room and hall both have wall thermostat wired in parallel, so either room can turn the boiler on, I have 9 programmable TRV heads in the main house, at the moment non linked to the boiler, but now with a Wiser Wall thermostat, I can replace the programmable TRV for a linked programmable TRV head in any room which is cool.

Non linked heads are that that expensive a google found this one at £15 each, linked more like £60 each, but they don't all have to be linked. I have eQ-3, Kasa, and Energenie, I will replace with Wiser TRV's which are linked, but at the moment Nest Gen 3 in the hall as wall thermostat and Wiser in Living Room as wall thermostat, and it seems to be working well. In 2019 when I got eQ-3 bluetooth they were £15 each, but brexit has bumped up the price, there is the Terrier i30 if you want to buy local. The Kasa seems to work well, not so keen on the energenie ones.

My radiators also seemed hot, and house was not getting warm enough, but found the boiler was being turned off before room warm, and hall heating up too fast, and also hall cooling too slow, second thermostat cured it for me.

 

[robinbanks]

Pressure in the heating system has dropped and needs to be topped up.

Problem was occurring in 2009; I guess it's either resolved or OP has passed from hypothermia by now

 

[ericmark]

Sorry, missed date, I must admit I had not expected my own heating to improve so much by adding a second thermostat, had not realised the heating was turning off, thought it was just the water was hot enough so boiler turning off, which if that is reason then pump still running just boiler off.

The Nest report is rather useless, the TRV head report does better show what is going on, as does the other thermostat but back in 2009 I did not have anything like this, I was having problems back then due to fitting CFL, with the old tungsten turning on the lights produced inferred heat, so set thermostat to 18ºC all day, and the lights boosted this in the evening, but when we changed the bulbs, we also had to change the thermostat, went for a programmable one I am not convinced using CFL (now LED) saved energy, as air temperature went from 18ºC in the evening to 20ºC in the evening, so air changes lost more energy. But this is progress we are told?