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I had a new combi boiler fitted 4 years ago with the HW plumbed in and working fine. I've now plumbed in rads, filled and bled the CH system, but I'm getting no heat in the rads or pipework.
It's a two bedroom flat and I've got a flow and return pipe to one end of the flat with the rads coming off one pipe and joining the other. A 'T' on each pipe makes a flow and return to the other side of the flat.
When the CH is on, the flow and return right by the boiler get warm/hot, but this heat doesn't circulate around the system. I've bled the pump and checked it's rotating - it is and it's hot too.
I've pressure tested it up to 3bar and released the pressure down to 1.5bar and bled the rads again. I haven't yet connected a thermostat to the system (not sure where to), but the boiler's got it's own thermostat.
My boiler is a Worcester 24Si II.

Any ideas?

have you definately got a flow and a return going to each radiator ?

pressurised systems aren't normally a problem to fill and heat. Are both isolation valves on the boiler turned on ?

Thank you so much.

I've confused myself so much reading the boiler manual and turning this on and this off, that I'd left one of the isolation valves off!!

Heat is now flowing round the system and my girlfriend loves me again.

So simple, but so frustrating I almost called a plumber out - thank you.

Will it be OK to run the system without a room thermostat? All the rads have TRVs, bar the hallway. I'm planning to fit one there, but not sure where it wires into the boiler. Also what wire do you use? On the diagram it looks like telephone cable, but neither the boiler or thermostat insructions show how to connect it.

Any ideas?

And thanks again.

New installations require a room stat because of energy efficiency. I shouldn't really say this - but I wouldn't bother fitting one.

I work in houses everyday and there's not many people actually use the room stat - they're normally turned up fully and forgotten about ( that's the best way i think) use the boiler thermostat to control the heating temperature)

If you do want one, the radio frequency (wireless) one's are good, you wire the receiver into the boiler and the actually room stat can go anywhere.

Thanks for the tip, I didn't want to blow my boiler!

I'll see how we go with the room temps without one.

I haven't added any inhibitor yet. The system's mostly polypipe, but I assume any rust etc would come from the rads, so I guess I'd better get some in there.

Do I have to drain the whole system or is there an easy way to do it?
And where do I add the inhibitor, can I poor it into any rad or does it have to go in at one of the boiler feeds?

Thanks again, it was great coming home to a warm house.

Isolate and drain one radiator. Reconnect it to the valves but leave them off. Remove the blanking plug from the top and add inhibitor (concentrate from a cartridge is easiest). Put the blanking plug back in and turns on the valves. Run the system for a few minutes to get the inhibitor circulating and then bleed the air out of the radiator. Check the pressure and adjust as necessary.

Which radiator you choose is up to you. Towel rails are easier because the plug is in the top rather than the side. Remember to protect carpets from any leaks or choose a room with vinyl or tiles on the floor. If it's more convenient, you can remove the bleed plug rather than the blanking plug.

Thanks for the tip, I'll do that.

Cheers