temp racing up on worcester

[crompton]

Any advice welcome guys - my regular guy is on holiday and the installer (not the regular guy - long story) isn't answering his phone.
May be relevant but the boiler, worcester cdi30, was cycling on&off way too much - usually 45-60 secs a time.
Yesterday I unjammed a valve on a room that'd been out of use a good while - realise I may have released a bucket of sludge.
Now, no heating or HW, but, boiler fires up, temp rockets to 100 & above in seconds. One of the pipes underneath gets hot, then it cuts out, heating receives zero benefit. Also I pressed boost button and it make a pretty horrid set of noises, first like a washing machine full of spanners (or a well tuned Transit) then a funny sound like dropping sand through a colander.
Sorry about the long Q but any advice - or pity!
btw, I'm in East London. Assuming this isn't a job for an amateur, what would it cost to fix?
and another btw, there are two white taps/valves by my outside drain. Are these drains for the heating?

 

[gigz]

Circulation problem by the sound of it, have you checked the pumps bled and spinning ? Bleed the rads and top up first.

 

[crompton]

wasted one bottle of sludge cleaner - stopped the water, opened the drain taps - put in the cleaner, filled up - but it wasn't in the system was it?
Next time I did the same, then opened up the bleed points so some rads drained, got the cleaner in the system.
Next time I emptied it was filthy. Pain filling up though, bleeding it out a dribble at a time. And cos the sys only has the bit of pressure that comes from the gravity of the header tank, slow process.

 

[gigz]

If its that bad it may need a power flush, you could try draining it fully, add some x800 (or similar) and leave in for a few weeks. You'll still need to free the pump though to circulate it.

 

[crompton]

still trying to get rid of the sludge, drain and fill, drain and fill. Figure ecvery time it empties dirty, some sludge is leaving.
Still slow and iffy. Fills so slowly, most of the time, the stat is calling for heat but the boiler's not on, keeps giving me a signal for syphon fill, which means boiler on min output for 15 mins. Mystery to me. Just want it to limp to the new year when I can get someone in who knows their onions. My regular guy doesn't know this model and isn't reaaly at home with all the s'ware diagnostics. Maybe just need a WB guy.

 

[crompton]

This doesn't get any simpler.
Been slowly bleeding the air out for about two hours now, boiler(worcester bosch 30cdi) keeps showing the symbol for syphon fill program which puts it on min output for 15mins. Is that significant? If so, what does it signify?)
Still most of the time the stat is calling for heat, the boiler isn't firing.
My life might be simpler if I retrain as a CORGI.
Any ideas? I added Sentinel x400 to the sys today after two doses of big shed drain cleaner in the last two days. Any reccomendations for how long I should leave it in?
And one more puzzle: when I was cleaning gunk out of the header tank that'd come through the header overflow, it was all pretty gravelly, and much of it was bright green. Is this some copper-related thing?

 

[mcmarshon]

sounds like your cold feed is partially blocked causing slow filling/pressurisation of the system. You would probably need to cut this pipework out and replace as this is very hard to clear. If you could get mains pressure on to it somehow it may help.

The worcester syphon fill program works, as you have described, when the power has been interupted to the boiler (i.e switched off) You can get the boiler firing by putting it into chimney sweep mode but this may not be such a good idea if you havent got much water/pressue in the system. Wait till the syphon program finishes and dont turn the boiler power off again.

 

[crompton]

Ta
if i replace the cold fill, is that right back to where it picks it up from the mains?
how would that get blocked - wouldn't that be out of the loop for rad sludge?
cos each time i drain, the stuff out of the drain points is really disgusting foul brown muck - and the heat pattern on some rads is pretty well how some people on here describe sludge probs.
thanks though,M

 

[mcmarshon]

The feed is from the bottom of the header tank, usually a 15mm pipe. the 'cold fill' as you call it is mains cold water running into the top of the header tank via a ballcock to control the flow & fill level.
Basically every time you drain the system you are allowing all the poo from the header into the system.
Its better to isolate the cold fill to stop the header from filling and then clean the header out so that when you fill it for subsequent flushing you only get clean water back in. You will find that you will be flushing for days to get it clean from the header if you dont do it this way. Syphon it out into a bucket then use some old rags to wipe out all the sludge.

 

[crompton]

thanks guys
helps to understand the ins and outs a bit better. After two days with Sentinel in there, hopefully loosening and moving the sludge a bit, just drained (again) fingers crossed for better circulation this time.

 

[crompton]

And one more puzzle: when I was cleaning gunk out of the header tank that'd come through the header overflow, it was all pretty gravelly, and much of it was bright green. Is this some copper-related thing?

 

[Hugh Jaleak]

Bright green stuff is possibly flux residue. Cold feeds can block, its often assumed as there's water in the F&E tank the system is ok, but the blockage prevents system topping itself up. As said, probably best to cut it out, you could clean the section and rejoin it for ease.

You dont mention if you've checked the pump, for the boiler to shut down that quickly is a sign the water is trapped in the boiler, so reaches temp very quickly and then the boiler stat kills the burner.

 

[crompton]

thanks
yes checked the pump, some bits of muck in there but nothing drastic, turning ok. Problem still mystfying though. Drained again, emptied header tank completely, cleaned out, all the sludge gone. Refilled, did a test fill and drain again, running through clear (but I have two drain taps outside and for the first time, only one emptying). Refilled, header looking clean, bled etc, fired up bouler, same problem again. Stat calling for heat but boiler only supplying intermittently. Sure boiler is ok though: turn off the CH & call for HW it goes like a train. Heating though only even reaching about four out of eight rads and one of them only a bit betterr than warm. TRVs all checked & open.
This stuff can drive you crazy. In-laws arriving for xmas in five hours.

 

[crompton]

just drained again, filled with sludge budger, once it's filled again it's staying there until 2010, 10mph boiler or not. Happy Christmas and NY and thanks for all the advice.

 

[crompton]

If anybody can be bothered reading back through the thread, here's where I'm up to.
Had sludge remover in over xmas, cleaned it out today, filled and drained twice, liquid running sometimes very pale brown, later more or less clear, though I have two outside drain taps, don't know diff, but right running strong, left sluggish then stopped.
Boiler going as before - sure boiler not the prob as works pretty well on HW only, but CH still hopeless. No pressure - open system - so where would the pressure come from? and some rads just don't fill, some heat ok, some upstairs, tiny bits of heat get through, and boiler stops firing long long before stat stops calling for heat - in fact stat set at 18 & CH never gets there so stat never stops calling.
Any more suggestions guys?
Thanks and happy NY.