Ferroli Combi running constantly????

[ParrDi Gras]

I have an Old Ferroli 77f combi bolier. we have had it set to Hot Water only for the past two months(due to the weather). Yesterday the boiler started making a banging noise , the temperature gauge has rasied to 100c, the boiler is not responding when I turn the temperature gauge down (you usually see the flame in the boiler decrease or increase depending where you turn the contol).And even though it is on hot water only the radiators are coming on!!! Usually the boiler only kicks in when we run a hot water tap then goes back into Standby when no hot water in use. I have tried switching the control knob to Timed Heating/Hot water and over to continuous heating/Hot water then back to Hot Water only but this has no effect. Ive also noticed that when the boiler starts to bang the pressure gauge is jumping from 1 bar upto 2 bar. Ive had to turn the boiler of at the fuse box and when I need hot water I have just turned it back on until I have enough water. Any help would be appreciated before I call an expert so i understand what the problem may be.

Regards

Steve

[Bernie2]

Can't obviously say for sure.

The banging is usually caused by overheating.

But basic things first.

Has the system got any water in it? When the system is cold does it read about 1 Bar on the pressure gauge?

Then is the pump working if the system has got water in it?

I would at this point suggest, if the boiler is reaching 100C the regulating thermostats that control the boiler heat adjustment settings have gone, it could be one or both, the central heating limit stat could also be faulty, because it appears, the boiler over heat safety thermostat seems to be shutting the boiler down, instead of the heat control stats.

Thats probably all the banging and noise are about.

Its dangerous to leave it and requires immediate attention.

Get the boiler looked at, even if its only a water shortage, which I must say I doubt, fill it up.

And once again I doubt its the pump, but get it checked anyway. I would say its most likely one of the heat control stats.

The reason I say this, is because the boiler should shut down quite a bit before it reaches 100C for safety reasons, and the first stat that should shut it down, is the control stat dependent on what you have it set on i.e. heating or hot water.

Even the safety overheat stat should cut off much lower than 100C. But then the temp gauge may be affected by the general temperature rise.

So get it all checked out.

An overheat stat is usually about £10. Other stats vary quite a bit.

[ParrDi Gras]

Thanks Bernie, would this also be why the radiators are coming on and getting very warm quickly when the switch on the bolier is only set to hot water??

[newbie1]

if the rads are coming on then it sounds like divertor valve as well..how old is boiler???i would hazard a guess that the boiler sounds shagged

[Bernie2]

Yes could well be. Overheating can cause all kinds of odd problems.

Unfortunately the rads getting hot could be caused by a few things, the diverter valve for instance.

But it may not be that, it may just be excess heat trying to dissipate on the central heating side by forcing the diverter valve slightly open with back pressure.

Lets hope its not done any damage.

It should become clear if there are further problems when the thermostat is fixed.

An outside chance is that the PCB might have gone west, electronic parts don't like heat much.

That may be a cause of loosing complete boiler control. But with a faulty stat your temperature control can be all over the place and shut everything off anyway and make it look that way perhaps.

Its hard to say exactly what is wrong, unless you can check it all out.

But if thermostats are designed to trip before they reach 100C, its fair to say there is a problem with the stats somewhere.

Overheat stats usually shut off at about 92C if the high limit stat fails at about 83C.

So if your getting readings of 100C it seems conclusive that there is a stat problem.

As to the possibilities of further problems caused by the boilers high temperatures I can't say for sure without fault finding the boiler.

Anyway renewing the stats are the cheapest option to start with.

Lets hope the diverter valve and PCB are okay.

If they are not, ask for a price to fix as its going to be a bit dear and an old combi boiler may not be worth it.

[ParrDi Gras]

Thanks for the advice guys , plumber comingon Friday , at least I have some sort of knowledge for when he starts chatting

thanks again


Steve

[puddle]

soumds like hot water flow switch sticking or gas valve letting by

[Bernie2]

Yes Puddles right! Could be loads of things.

If the gas valve is stuck open and letting by, it won't shut off and keeps the burner going. If the hot water flow switch is telling the boiler to heat the hot water all time the same thing. Both conditions of which could cause the symptoms you say. But whatever it is the boiler is not responding to its normal thermostat call channels.

Its a bit like a doctor trying to decide whether the patients has a head cold, flu, or something worse, the symptoms are roughly the same and you can't really tell without being there to look at it.

[ParrDi Gras]

Hi agian guys. Had the doctor round and he seems to think the combi boiler has died on the operating table.

Advised me to get a new boiler which is half what i expected given the age of this one as he thinks repairing this one would cost as much .

Ok, so Ive trawled throught the catalogue we have at work ( fortunately I work for Saint Gobain which owns Grahams the plumbers so get decent discount) and have been recommended a Vokera Compact 35HE by the local grahams branch manager. he tells me they are a decent boiler with a good flow rate at a reasonable price (even better with my discount) just wondered if you guys had any thoughts on Vokera as its not a name im familiar with. For a comparision a Worcester or Glowworm boiler with the same sort of power & flow rate etc etc cost £200 plus more.Anyone had any experience of these boilers???

Thoughts would be appreciated

Regards

Steve

[newbie1]

take a look at the new vaillants have been doing a few ecotec plus 824 and they are preety nice boilers