Worcester Bosch 30si

[Bankrobber]

I had the above combi boiler installed in October 2009 and it is working perfectly providing heat & hot water as required. However it has developed a dull clunk when running on low power ie when hot tap is only turned on low or heating is running slowly to keep set tempearature. When boiler is running on full power ie hot tap opened fully or heating coming to raise temperature several degrees. there are no clunking sounds.

Does anyone have any idea what this might be or is it normal? I have not called Worcester yet as boiler is working perfectly, apart from the dull clunk?

 

[ianniann]

How often does it clunk? Is it from inside the boiler case, or perhaps somewhere along the pipework?

 

[Bankrobber]

Definitely coming from the boiler and every few seconds when it starts, can the pump make a clunk when running on a slower speed or does it run the same speed all the time?

 

[Gasman77]

No the are fixed speed on the si. Is it when you run a tap? could be the div. valve moving

 

[Bankrobber]

Makes the dull clunking noise when the boiler has modulated vey low on heating or hot water.

 

[bellairaphon]

more than likely the pump on its way out. the clunk will be coming from the heat exchanger with the case off youll hear it

Nath

 

[Bankrobber]

Thanks Nath, yes i thought it was possibly the pump, but there is no clunk when the boiler is running on full power? Is it common for a pump to start to fail after 6 months? I should ring Worcester under the guarantee then?

 

[bellairaphon]

it depends on the system really how and if it was treated correctly. but to be on the safe side id drop some x100 into the system before the wb engineer comes round. ive been to few recently bit older then 6 months but same fault or what sonds like same fault. aslong as the heatex has been vented then i would def say pump.

Nath

 

[Bankrobber]

Not sure if the Heat exchanger was vented, is this something I can do or leave to the WB engineer? I did have to drain the system recently to replace a leaking rad valve & did add X100 on refill.

 

[bellairaphon]

yeah you can do it. take the outer case and at the top off the heatexchanger youll have a white tube place this in a bucket at some kitchen roll on the gaurd open the vent by turning anti clockwise till water comes out then shut it off and get all excess water out. also make sure u vent the pump.

Nath

 

[45yearsagasman]

Whoa! A six month old boiler under warranty.Advising a user to remove outer case which has a combustion seal would not be my advice.Call in the WB engineer.Am I being over cautious? I don't think so.

 

[mcmarshon]

Is that you Bernard ?

 

[45yearsagasman]

mcmarshon,this forum is for people to get help from experienced gas engineers.Your comments do nothing to contribute to this.

 

[mcmarshon]

Lighten up old boy, no harm intended !

 

[steved101]

maybe it;s the gas valve making the cligking sound.

If the pump was failing then you;d get obvious signs like overheating/boiler lockout rads not so hot etc - check the resistance of pump