Alpha CB50 Boiler exploded today

[lawrenso]

Our 4.5 year old CB50 exloded today. The expansion vessel for the Central Heating side totally blew out. Luckily the boiler is located in the garage and nobody was in there at the time as the cover blew off the boiler and boiling water was spraying all over the place

The Transco engineer said he had only seen one like it before - the BG engineer said he had not seen one blow so badly before. They have said they can get the parts for Monday, but after several months of issues with the boiler, we have lost all faith in it.

What would be a good replacement for it.

We have 17 radiators, Kitchen, Utility, Cloakroom, Main bathroom (soon to be with thermostatic shower), En-suite with Thermostatic and another En-suite with electric

Thanks in advance

Steve

 

[Agile]

I have now seen four after they had burst open.

However, they dont just fail !

They only fail if the filling loop has been left open or leaking.

You are lucky that you seem to have BG cover and that they are apparently going to cover the repair.

Tony

 

[gas4you]

Have a look at the Vaillant Ecotec Plus 937, or if you want quailty with no cost implications look at the ATAG Q series.

 

[BigBurner]

Our 4.5 year old CB50 exloded today. The expansion vessel for the Central Heating side totally blew out. Luckily the boiler is located in the garage and nobody was in there at the time as the cover blew off the boiler and boiling water was spraying all over the place

The Transco engineer said he had only seen one like it before - the BG engineer said he had not seen one blow so badly before. They have said they can get the parts for Monday, but after several months of issues with the boiler, we have lost all faith in it.

Why didn't the Pressure relief valve blow first? Make sure they replace the pressure relief valve. If this failed to open, then I would insert a tee near the boiler and fit another relief valve of a quality third party maker. If one fails the other will catch it. The pressure vessel is the last line of safety in a CH system. It is meant to blow after all else fails.

As been said make sure the filling loop is disconnected from the cold mains. Main pressure water - up to 9 bar in some places, can enter the CH system if the loop fails.

The CD50 and CD50 are reasonably reliable boilers. Nice flowrate. Get it fixed and see how it goes.

What would be a good replacement for it.

We have 17 radiators, Kitchen, Utility, Cloakroom, Main bathroom (soon to be with thermostatic shower), En-suite with Thermostatic and another En-suite with electric

Don't go for the Vaillant 937, the performance is far less than the CD50, you will be disappointed. You want something as equal to it.

Look at the high flow rate Ethos 54C combi. It will supply what you need. http://www.ethosboilers.co.uk/products_54c.php
The Worcester Bosch 550 floor mounted unit will be good too.

Two 24kW combis will do and be cost effective. In DHW, one doing a bathroom each. One doing the kitchen, one doing the utility. Join the outlets for the baths using two check valves and a small shock arrestor. Also one can downstairs CH and one upstairs, giving CH zoning. Upstairs and downstairs then can be timed 100& independent - but more upheaval splitting the CH system. But worth it as cheaper to run and backup using two boilers.

But I would stick with the Alpha and put in a second Pressure relief valve.

 

[Paul Barker]

Depending where you live I'll come and unplumb the Alpha and take it away. Then your installer has less work to do.

 

[BigBurner]

Depending where you live I'll come and unplumb the Alpha and take it away. Then your installer has less work to do.

Now there is a powerful argument to keep it.

 

[Paul Barker]

I'm staying out of it

That boiler you linked looks interesting. Do you recon the callorifier is a small pipe coiled inside a coiled large pipe? Must be something like that.

Only problem I can see with the maximum power one is the gas supply requirements. But it is the maximum power one they need.

 

[nickso]

Why didn't the Pressure relief valve blow first? Make sure they replace the pressure relief valve. If this failed to open, then I would insert a tee near the boiler and fit another relief valve of a quality third party maker. If one fails the other will catch it. The pressure vessel is the last line of safety in a CH system. It is meant to blow after all else fails.

alphas use a caleffi PRV, hardly unreliable and no one knows what pressure this got to before it blew the EV. i'd put money on it being a faulty EV rather than a faulty PRV.

OP,get them to change it and forget about it.

 

[Paul Barker]

What wa sthe routing of the discharge pipe? Is boiler in a cellar? does pipework go uphill? Was it forzen?

I've seen one of these boilers fitted in a cellar with upward prv discharge peipework and unvented discharge not even connected.

The installer of this boiler must have the unvented ticket as it is an unvented hot water store of more than 15 ltre storage. Conversely some of the storgae combi systems are thermal stores which don't require the ticket.

I have once had to change an EV for a cd50. No big deal. Change PRV and check clear flow and routing of discharge pipework.

All easy work unless boiler was installed below a level from which adequate continuous fall can be achieved to drain.. If in error then move boiler or install a sump and pump arrangement. Or change boiler for one which does not include unvented hot water storage and sue installer.

 

[Agile]

All the boilers that I have seen with burst EXVs have had apparently normal PRVs.

Whilst I have not done any tests, it seems that overnight the mains pressure can get so high that the pressure inside the EXV can get to the 6 Bar at which it may rupture EVEN though the PRV has opened and is letting water out.

I will shortly go to a most interesting case. The daytime mains pressure is so low that I can hold it in the kitchen tap with my thumb! Its possible that I will not be able to come to any conclusion.

Tony

 

[bengasman]

If the pressure under any circumstances a properly installed boiler can explode, even an ideal, would that not make them qualify as: not fit for purpose? Especially when it is not an isolated incident.

 

[BigBurner]

I'm staying out of it

That boiler you linked looks interesting. Do you recon the callorifier is a small pipe coiled inside a coiled large pipe? Must be something like that.

Yes they do not use a plate heat X for some reason, although the coiled copper tube heat X works very well though. Yes it is pipe-in-pipe.

Only problem I can see with the maximum power one is the gas supply requirements. But it is the maximum power one they need.

He has the combi in the garage - I assume the meter is not far away.

The Ethos is a superb quality combi. Built in weather compensation - all you do is link the outside temperature sensor. It can have plastic flue extensions and a DHW secondary circulation loop kit fitted to give instant hot water at all taps.

Superb Flow rate.

Something tells me this system (17 rads) needs an extra expansion vessel, as the one on the Alpha is too small. This must be checked. The filling loop MUST be disconnected after filling.

 

[Biggles..]

The Ethos is a decent unit if installed out of the way, the need for an external expansion vessel and prv becomes a pain when tying to site in kitchens and utilities.External bypas also required.

Oh and the 25litres is based around 2bar pressure

 

[BigBurner]

All the boilers that I have seen with burst EXVs have had apparently normal PRVs.

Whilst I have not done any tests, it seems that overnight the mains pressure can get so high that the pressure inside the EXV can get to the 6 Bar at which it may rupture EVEN though the PRV has opened and is letting water out.

I will shortly go to a most interesting case. The daytime mains pressure is so low that I can hold it in the kitchen tap with my thumb! Its possible that I will not be able to come to any conclusion.

You can. If the pressure and flow is so low then a solution will be a small accumulator.

 

[lawrenso]

Cheers for ALL the replies. A bit of further information for you. As mentioned in my earlier post we have had a few problems with this boiler and also a few problems with British Gas. They took payments from me without arranging a take on inspection, then when I called them out after 11 months, they came and at first tried to refuse to take on the boiler saying it was BER, would take too long to fix (had corrosion around the top inlet on the storage tank, running outside). I had to quote Contract Law at them - then they came out and only replaced funny enough the PRV from the said same expansion vessel - all of 10 minutes!!. This was dripping to the outside and was pointed out to him by her indoors and the engineer said that it was OK!!

We then had to have the storage tank replaced a couple of months ago due to it leaking from the top valve where the corrosion was - this would of meant removing the expansion vessel. - which he re-secured with a bit of nylon washing line and he lost the screws for the front cover to be rescured on - telling the misses I said I would do it later!!

The Transco guy pointed out to me that the overflow pipe was frozen as to the cause. I have a nice chunk of ice with pebbles in it (the overflow is about two inches above ground level and it had an icicle down to the ground into the pebbles around the house). The BG engineer then said that wasn't the cause of it!!

They are due tomorrow with the spare parts and a boss as well as an engineer and I will be looking for somebodies scalp over this. I also want a complete and thorough investigation into the complete boiler.

At the end of the day one of us could of been in the garage when it went.