HELP! Rad disconnected , now no Central heating! 28CDi

[Reg Hedge]

Thanks in advance guys! Also apologies if this fault has been covered before; I couln't find it.

The Boiler is a Worcester 28CDi RSF Gas Combi approx 7 years old.

Quick version:-
Disconnected & reconnected downstairs radiator yesterday, re-pressured system, and CH seemed to work OK. By last night it stopped working and hasn't worked since. DHW is fine from same boiler.

Longer version:-
Took downstairs radiator off, but had some trouble with the inlet pipe (if that's the right phrase?) Couldn't completely stop water coming out while rad was off, so a fair bit of the system water might have been lost. Got rad back on fairly quickly though, and once I'd repressurised the system (using the plaggy key and inlet knob under the boiler) I assumed it would be fine...same as I've done on several occasions before. Incidentally, I needed to wash hands while rad was off, and the DHW was NOT working, although it was fine as soon as the system re-pressurised...dunno if that's relevant here.

Once done, the CH seemed fine, bled the rad, and the whole system seemed to warm up pretty quickly....although I did notice all the rads were warmer on the top than the bottom. Unfortunately, after an hour or two I realised that the rads had gone cold again, and they wouldn't come on again even with the thermostat turned right up.

Boiler seems to be perfectly OK with DHW; no strange noises, flashing lights etc. If It's switched off at mains, and then turned on again, it mananges a click and a whirr for just a split-second (as though it's about to leap into life) and then..nothing.

 

[tryitandsee]

It may be just one of those unmoveable airlocks in the central heating circuit, try draining down again and filling slowly bleeding each rad again.

 

[Reg Hedge]

Ok - thanks I'll try it.

Sorry to sound thick; do I drain the system from the boiler itself?

TIA

 

[hav it]

hence the hole problem in the first place?????

 

[Reg Hedge]

hence the hole problem in the first place?????

Sorry?

 

[ChrisR]

I don't believe an airlock in a sealed system which stops heating working.
COuld be that the pump is blocked with sludge or knackered, or there's some sort of sludgy blockage.

But if you turn boiler off, wait, turn it on and it works on HW , yes?
Pressure guage rises when it should and says about 1 - 1.5bar, yes?
Turn CH on. DOes the fan start?
Look in manual for the system flow switch - brain fade this morning, forgotten where it is. That should respond to pump running, if there's circulation.
If the boiler doesn't even try to get going for ch , it's broke...

 

[bengasman]

If the rads stay cold at the bottom, you have a soiled system. If the boiler has been running for 7 years without being flushed properly when installed, the pump is gone or dying. Try what happens with all the rads turned off bar the one nearest to the boiler. Fairly high pressure, 1.5 – 2 bar may help to get rid of air bubbles. Make sure you do not overpressure the system. Put some non corrosive cleaner in the system and see what happens when you run it. another give-away is ph-test. If under 7, your system is almost surely corroded and full of sludge. Ditto for pump.

 

[JohnD]

when you took the rad off, was it full of black water? And was there black sludge?

 

[tryitandsee]

Taking the down stairs radiator off and then putting it back on again will have caused water from upstairs rads/pipework to drain down and partially fill empty rad. As probably no air was allowed into the upstairs radiator to ease its passage an awkward airlock/pocket/deadleg has formed, Drain down again and start from scratch. It may be a good idea to have all upstairs bleed nipples open. Start filling slowly, when downstairs rads full, do upstairs.

 

[Reg Hedge]

Thanks for all the responses - very much appreciated.

Just to give you an update....it seems to have spontaneously fixed itself! Woke up this morning to find all the rads working fine. They are still slightly warmer at top than bottom, so I think a full system flush might be a good idea, but I think I'll get a pro in to do that for me.

Just to say, the system was treated with Fernox (?) when new, but I've topped up the system on many occasions since, so it will have probably diluted to nothing by now. Water coming out of rad seemed reasonably clear, although the last few ml were dark, but I wouldn't say sludgy.

Co-incidentally, Worcester recently sent me an offer for CH maintainance plan. Worth it?