DIY Doctor UK DIY Forums

Please bear with me as this is my first post.
Firstly i have a Worcester Greenstar HE combi boiler with a Siemens RDJ10 room thermostat fitted the boiler was serviced this summer and the thermostat was fitted new tonight. I have 4 rads upstairs and 5 downstairs. All have TRVs except the lounge and dinning room.
The problem i have is that the system doesnt seem to be able to cope with heating all the rads at once even though when fitted some 6 yrs ago it was great. Now i dont have the bedrooms heated but it still struggles to heat the remaining rads. Now if i turn on one or two of the bedroom rads just onto freeze protection the dinning room and bathroom go cold.
One thing i have noticed and the reason i bought a new room thermostat was the boiler when heating the house keeps switching off when it gets to a certain temp then back on again when the temp drops to a certain level. Is this normal even though the room thermostat is asking for more heat?
I really hope someone can help as it is sending me up the wall

Thanks

Hi Gibbsy,

What is the pressure reading on the gauge??
Do you have any other contraptions fitted to the system.
You say sealed, but do you have a copper cylinder etc.
As you can see -- need more total info

Hi steve

The pressure gauge is reading just above 1 bar, there is nothing else fitted apart from the room therm which i mentioned and i dont have a copper cylinder fitted.
It is just the boiler and 8 rads in a 3 bed semi to heat the house and provide hot water.

Has anyone been fiddling with the lockshield valves (the "tap" at the outlet side of each radiator). Sounds like the radiators are out of balance. See this article to sort or google "balancing central heating".

Thanks for the tip it seems that all the lockshield valves were wide open and so putting the whole system out of balance. Just when i thought it was sorted i got home last night and the bathroom radiator was stone cold after it had been fine for days, any ideas anybody.

Thanks for all the help so far.

Gibbsy

Do you live in a hard water area?
Could be scaled up in the boiler etc
Poss drain down > cleaner for time spec> drain again> inhibitor.

Hi Steve,

I dont live in a hard water area but i think i will go with your idea anyway as it has never been done in the last 6 yrs since the system was fitted and only then had the rads and boiler fitted as new all the old pipe work remained.
So maybe its time to give it a little TLC.

Thanks for the reply will let you know the out come.

Cheers

Gibbsy