Worcester 24cdi - weird banging noises, then shutdown

[Dave Fraser]

I'm running out of patience, 5 different engineers and its still not fixed. (Insurance cover)

The boiler is 18 years old but has virtually been rebuilt. New gas valve, new water to water heater exchanger, new diverter valve assembly (inc. new style filling loop) new expansion tank, new burner.

Issue - from cold. Demand hot water - the pressure (on the gauge) rises slowly at first, boiler makes a whooshing (pressurising) sound (sorry, poor description) the pressure gauge then increases rapidly, bang whoosh bang, flames go out, both red lights illuminate - no hot water.

Exactly the same happens for central heating.

If you attempt to try again (for either HW or CH) the boiler spits hot water from the relief valve on the top of the boiler.

This is the weird bit... if the circulation pump is running (prior to requesting HW or CH) everything works fine, absolutely 100%. In the past I managed to "trick" the pump into running just to get it to work...

I'm a qualified aircraft engineer (B1 & B2) and its driving me nuts. I know I'm not 'qualified' to work on the boiler but the engineers that have been sent out are failing to fix this and I've been told the entire boiler needs replacing... The insurance company have (finally) agreed to one more engineer visit.

Help please..... at least I'll be able to tell the next guy what to do next (I hope?)

Much thanks, Dave

 

[rochdalegas]

All those parts and the pumps never been changed?

 

[Dave Fraser]

Nope, I suggested this but was told that the pump is fine. A new pump was fitted 6 years ago, it's not the original one.

 

[rochdalegas]

Without carrying out various test its hard to diagnose over the internet but it sounds like the pump to me either the pump itself or its getting a intermittent supply via the wiring harness or pcb.

 

[Dave Fraser]

I appreciate it's difficult to diagnose and also appreciate your help and advice too. The first engineer checked the pump and said it was fine and that the pump isn't involved/needed for the HW anyway (not my words, his)

I suggested "pump" to the third engineer and he poo-pooed that saying "it's running fine and not required for the HW"

Maybe I'll change the pump myself?

Am I ok to do this? I won't be disturbing the gas..

Thanks again for the help, much appreciated

 

[easyflow]

I,ll go with rochdalegas (pump).

 

[rochdalegas]

If youre unlucky enough to get engineer 1 or 3 back ask him how the water gets around the secondary heat exchanger? If your proficent with electrical testing equipment check there is a live to the pump when their is some demand on the boiler.

 

[Dave Fraser]

Thank you all very much. Waiting to hear when the next "engineer" is coming...

So, when the boiler is cold/nothing running, is the hot water "pumped" round the boiler when you turn on a hot tap?

In the mean time I'll check supply to the pump...

 

[moh222]

It may not be as simple as checking supply to pump. Most modern boiler pumps have multiple pin connections to the pump, ie. as well as the power they have additional connections for pump speed etc so without the wiring schematics for the pump connections it may be very hard to check.

 

[Dan Robinson]

It may not be as simple as checking supply to pump. Most modern boiler pumps have multiple pin connections to the pump, ie. as well as the power they have additional connections for pump speed etc so without the wiring schematics for the pump connections it may be very hard to check.

You might want to check the model of the boiler in question.

 

[Dave Fraser]

All fixed (I hope) pump changed and the boiler working fine on both HW & CH, no more banging (overheating).

FYI the circulating pump is required when you demand HW!

Many thanks for your help and advice, much appreciated.

 

[Dan Robinson]

FYI the circulating pump is required when you demand HW

We knew that. Shame that the dumbass from your call out firm didn't

 

[Dave Fraser]

Thanks Dan, I am now certain that it was a scam by the insurance co. to sell me a new boiler etc etc. Not happy and have requested a full refund of all premiums.