Not enough Heat

[Wagger]

We have recently had oil fired central heating installed.
All radiators have TRVs. We also have a system thermostat inthe hall, set at 25 degrees.
When the heating is first switched on all radiators becomehot or very hot but our rooms and the main thermostat reach only 19/21 degrees.After around 2 hours the radiators furthest from the boiler start to cool andwhile they warm up intermittently the rooms never get above 19/21. All TRVs areset at 5.
The system has been balanced and we are satisfied that thisis not a boiler problem. Our plumber is stumped. Any ideas?

 

[rpm]

Can`t help I`m afraid, but thanks for registering and welcome to the forum Wagger.

 

[stevetheplumber]

i would disconect the room stat and see if the rooms get hot then if they do its a romstat positioning problem if they dont its either rads pipework or boiler to small

 

[joni os]

If not the room stat. Is your boiler modulating correctly.

 

[ShaunCorbs]

if boiler is still fired and furthest rad is cold not the room stat

 

[snowhead]

Was the system designed (radiator sizes and boiler size) to work at 25 degrees?

Is 5 the maximum on the TRV?

Is the boiler cycling on and off when the temperature is 19 / 21 or is it running continuously?

 

[Wagger]

Thanks. It looks wired in and I don't know how to disconnect it. However, the stat has been replaced and made no difference. We also tried increasing the temp with a hair drier and were able to do so. Of course, it could be a problem with the connection as the stat is wired into a complicated box and I don't know what is happening in there.

 

[Wagger]

Thanks Snowhead. Answers : I don't know for certain but it should be OK . However, I suspect in some rooms the radiator may be too small although not in others where ther is the same problem.
Yes 5 is the max.
Boiler is cycling on and off when at 19/20

 

[Wagger]

Sorry Joni os, I'm not an expert I don't know what you mean by boiler modulating.

 

[Wagger]

Thanks ShaunCobs. I'll check that out.