Halstead Quattro Gold boiler Loud banging on DHW ?

[weseeyou]

I can't seem to get this problem sorted .I have now completely stripped the boiler to clean out the primary and secondary heat exchangers and fit a new diverter valve. Hopfully another good flushing will cure this problem . The boiler is getting too hot and the water is not circulating quickly enough to dissapate the heat . I think the engineer increased the burner pressure for the DHW which may be part of the issue?

When I open a hot tap there is an immediate loud and voilent banging noise in the boiler which sounds like steam expanding ?

I noticed this morning that the previous engineer that worked on the boiler had refitted the automatic bypass valve on the wrong way round.

What would be the likely symptoms of having this valve the wrong way round if the boiler had a tendency to overheat ?

 

[diamondgas]

weseeyou, is the pump working ok, not full of crud, spinning freely....etc It's the heart of the circulation. Regards the noise issue hmmmmmm! Any dead-legs on the ho****er sysstem? When you turn the hot tap off does the flame shut down imediatly or stay on for a period of time? Just wondering if a dead leg is overheating the primary heatexchanger. Does the heating heat up ok? Flow doesn't get too hot too quickly kind of thing!

Questions, questions ...lol.

 

[weseeyou]

Hi thanks for the quick reply.

With all the noise it was difficult to tell if the pump was working all the time. When the over-heating first started the CH was definitely circulating properly but the DHW was definitely getting too hot .

When i last tested the boiler yesterday the pump was getting too hot and the water was definitely not circulating through the primary heat exchanger .There was no live feed from the pump relay so I bypassed the pump overrun stat so that the pump was running all the time the boiler was on . Although the CH seemed to circulate a little better it was still very slow to heat the first rads suggesting a blockage or airlock.

When i ran a tap with the boiler hot the burner increased to full and the hot water flow was good but within 10 seconds the banging in the boiler was so severe I had to shut the boiler off .
The boiler then tripped the overheat stat and ticked and clicked etc because it was so hot.

 

[diamondgas]

Anyone been messing with the modureg? May be worth checking the low and high fire burner pressures 'weseeyou'!

 

[diamondgas]

Ooops! just realised you said previous engineer had been messing with the pressures! May well be all it is ! Do you have the mi's?

 

[weseeyou]

funny you should say that !.
The local CH engineer I had round a couple of weeks ago fitted a new gas valve and ignition pcb.

When She adjusted the burner pressure afterwards I noticed that the DHW burner pressure was a lot higher than previously and she had adjusted it on the main pcb.
I have tackled her twice on this but she refuses to do anything more and insists I need a new boiler . Am I being paranoid if I suspect she increased the burner pressure to make the boiler pack up prematurely ?

 

[weseeyou]

Ooops! just realised you said previous engineer had been messing with the pressures! May well be all it is ! Do you have the mi's?

no I don't have any expertise in adjusting /setting burner pressure and I'm not GS registered hence getting her in to replace the gas valve.

 

[diamondgas]

no I don't have any expertise in adjusting /setting burner pressure and I'm not GS registered hence getting her in to replace the gas valve.

Well I'd get her back to check it again ... easy thing you can do is pull the two yellow leads off the gas valve modureg and see if that makes any difference!!! It should reduce the BP to minimum! If it doesn't then you need someone to set up the pressures for you!

What's your background? You seem to know a bitabout plumbing ... 🙂

 

[weseeyou]

Hi yes I installed heating and plumbing back in the 70's & 80's I've never attempted to commission though and get registered sparks and GS engineers to do that.

I'm only attempting to sort this problem because I cannot afford £2k+ for a new boiler as I'm now a full time carer for my Father who is disabled and has dementia.! Funny old world isn't it.

I know that eventually i should be able to get the old gal going again as it was working perfectly before a small leak got into the ignition pcb.

I've now replaced the Ignition pcb the gas valve, main pcb, all the sensors and stats, airflow sensor, microswitches and just about to replace the diverter valve.
Ive got both the heat exchangers soaking in descaler overnight , I've stripped and cleaned the fan, pump , and I've cleaned the burner assembly and when i put it all back together tomorrow I'm hoping it will work properly.

If not I'm going to take it to a quarry and blow it up lol

thanks for the tip about the mod reg valve

 

[diamondgas]

Report back with your findings my friend once you get it all back together! The manufacturers instructions explain setting up the pressures! Hand them to your gas engineer should they need to be checked and adjusted! good luck!

 

[weseeyou]

thanks for your help and advice . much appreciated.

 

[pobsdad]

Technically,we should all be shocked and tell you to stay away and trust your GSR engineer,but you seem to know more than her,and experience shows that experience means more than papers.The problems occur when something goes wrong,and insurance companies ask questions!And,if you take it to a tip and blow it up,are you quallified to use explosives?
It definitely seems like a blockage.If the soaking doesn't work,try filling the boiler with a dose of cleaner(sentinel,fernox,etc),and running a hot tap for 30 mins with the heating isolators turned off(if they don't leak!).This will circulate the cleaner round the boiler and ensure it gets to all the main parts.And definitely get the burner pressures checked! Not trying to find cowboys/girls,I could be wrong again,but the easiest way to convince someone they need a new boiler is to 'adjust' the pressures.

 

[weseeyou]

weseeyou, is the pump working ok, not full of crud, spinning freely....etc It's the heart of the circulation. Regards the noise issue hmmmmmm! Any dead-legs on the ho****er sysstem? When you turn the hot tap off does the flame shut down imediatly or stay on for a period of time? Just wondering if a dead leg is overheating the primary heatexchanger. Does the heating heat up ok? Flow doesn't get too hot too quickly kind of thing!

Questions, questions ...lol.

Steve I have just re-read this again and realised that I didn't really answer your questions.

Re the dead leg. ...The bypass from the ch return to the secondary heat exchanger which had the reversed auto bypass valve also feeds to the expansion vessel. I'm pretty sure that the EV hasn't been reated or charged for many years. Would it be possible for the bypass pipe and expansion vessel to become the dead leg you refer to ?
When the banging occurs it sounds like it is caused by the cold mains water passing through the diverter valve and the DHW heat exchanger and being turned to steam ? does that make sense ?

 

[diamondgas]

Would it be possible for the bypass pipe and expansion vessel to become the dead leg you refer to ?

No the dead legs I refer to are found on the domestic pipework. They trap air and cause the burner to stay on for a period of time when the hot taps are turned off. They could give rise to excess heating of the primary heat ex.

When the banging occurs it sounds like it is caused by the cold mains water passing through the diverter valve and the DHW heat exchanger and being turned to steam ? does that make sense ?

I think you've got your system design head a bit mixed here. There's a few things that couldn't happen .. bye-the-bye though!

 

[weseeyou]

As the banging only occurs when the hot tap is turned on and the cold mains passes through the diverter valve lifting the CH valve and diverting the CH through the DHW exchanger which immediately produces the loud banging noises I not unreasonably assumed that they were directly related ?

I am still not clear about what effect there would be if the automatic bypass valve was reversed . Its sure to have some effect when the boiler is overheating the way it is. if superheated CH water from the primary exchanger was tapped off before getting to the inlet on the diverter valve and instead of being diverted to the CH flow was instead fed straight into the top of the DHW exchanger because of the reversed valve ,then you opened a hot tap ?


maybe i'll never understand what is going on in this boiler. With the new parts fitted , the valve fitted the right way round and a flushed system I'll just hope its cured

 

[diamondgas]

I see where you're coming from weseeyou .... time will tell whether all the work you've done so far will pay dividends ... let us know how you get on!

 

[weseeyou]

apologies for not posting back with the outcome but just in case someone re-reads this thread in the future I thought I'd explain the outcome.

After having little success and having no HW or CH for many weeks I bit the bullet and completely stripped the boiler . I found that despite previous flushing , a lot of loose scale had clogged the diverter valve hence the kettling. Water heated in the primary heat exchanger wasn't flowing through the diverter valve and around the CH system hence the immediate overheating
I fitted a new diverter valve thoroughly flushed the entire system and boiler replaced the pump and it worked perfectly first time ! Took a week to clear the backlog of washing...