WB 24CDi RSF - Banging

Kevinh · 22 Aug 2004

Our Combi boiler is around three years old and now gives no DHW or CH. When switching on either the CH or DHW, the boiler starts fine - ignites and less than one minute starts to bang, the pressure gauge goes up and down and steam is emitted from the automatic air vent. The system shuts down but will attempt again to start but with same problem - Could this be the pump? Brilliant timing - no HW especially as just had new baby, being moaned at by the misses and other child of 4. Can anyone help please!

kevplumb · 22 Aug 2004

could well be the pump ,or the expansion vessel ,or lack of water

DP · 22 Aug 2004

Very few combi boilers will fire with little or no water in the system. Some will even play dead if pump does not run since pump start is the first event in the sequential operation. Expansion vessel is for accomodation of increased volume of water when boiler is running- fail to see how or why water will convert to steam if EV is cuffed. But then I have an open mind and come to this forum for education.

I would check if CH is functioning correctly, system pressure is correct (1.5 bar).

DP · 22 Aug 2004

kevplumb · 22 Aug 2004

read the first post

Kevinh · 22 Aug 2004

Thank you both for your replies and help. As the pump is in the 'startup' sequence I cannot hear it turning or is it especially quiet? I have checked that the mains power goes to it (on the pump connectors) when switching on the HW or CH which it does. I am going to buy a new pump as it's fairly cheap and easy to fit just to see. I understand the Bosch/Grunfos 15-60 has been updated.
Thanks again, any help with dirty kids...!

PEDANTICVINDICTIVEMAN · 22 Aug 2004

Before buying a new pump why not remove the big silver screw in the middle
of the pump and check the shaft is free by putting a small screwdriver in the middle and turning it, if ok turn on boiler and run to see if the shaft is spinning round, catch any dribbles of water with a cloth, if your handy turn off the valves on the heating pipes under the boiler, then drain the water in the boiler off using the drain tap, then you could remove the allen key screws and remove the pump head to see if the pump is blocked with any dirt, I have been to one where fibreglass had blocked the pump and gave similar symptoms to your problem.

Kevinh · 27 Aug 2004

Thank you all for your advice. I stripped the pump and found to be sticking, tried to clean out but only lasted a day. So had to buy complete new pump as Worceser-Bosch wants more profits and will not supply only the head! Tried a Ideal head first but physically too large (could not put the case back on).
Thank you again - Kids now nice and clean!

xiaxe · 28 Sep 2004

I have had the same problem with the same boiler , i just refilled the system and the problem has resolved ( fail point G ), if you don't have the manual i can send you instructions

However i have a new problem with that boiler , there is no ignition on startup ( in fact at all ), how it hapend

My gas supply was switched off and since then the boiler is howing fail point H ( if you have manual you'll no what i mean )

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WB 24CDi RSF - Banging

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