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Plumberpro, Mechanical Engineer
Category: HVAC
Satisfied Customers: 634
Experience:  Over 20 years experience in plumbing heating and gas
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I have a 28si 11 hot water working fine heating makes load

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I have a 28si 11 hot water working fine heating makes load banging noises when first turned on then makes sound like kettling then pressure gauge goes up have changed internal fill loop and prv pump working ok

.what is your pressure reading , please

JACUSTOMER-gtwjkryc- :

start it at 1bar but even with new filling loop it still rises after a while


Ok . your boiler has an expansion vessel. When the boiler system water is heated the hot water expands and pushes into this vessel( like a balloon in a metal case) . these vessels eventually go flat and the hot expanded water has nowhere to go .the pressure goes up and exits out of the safety valve to outside. So it gets refilled and etc etc. The vessel needs replacing if torn or repumping up. Think you are going to find that your pump has run dry and is not working properly, causing the boiler to overheat and make nettling noises

JACUSTOMER-gtwjkryc- :

can the vessel be recharged if so what pressure required I take it the vessel is the red one at back. Was just wandering if it was possible that it could be the pipe work going through the heat exchanger cheers


Yes it can be pumped up with a car tyre pump or strong bycicle pump up to 1.7 bar. Hot waters ok so it won't be the heat exchanger pipe

JACUSTOMER-gtwjkryc- :

Cheers ***** ***** that but not home now till Saturday



Plumberpro and other HVAC Specialists are ready to help you
Customer: replied 3 years ago.

Changed the auto air vent and set pressure on vessel to 1.7 bar but still same ??

Customer: replied 3 years ago.

Changed the auto air vent and set pressure on vessel to 1.7 bar but still same ??

, most likely your pump has failed . is it red hot to the touch? If you open the bleed screw , is the pump impellor spinning?
Customer: replied 3 years ago.

Yes the pump is spinning does feel warm cheers

pressure to shoot up and to have kettling noises this shows overheating, like a no low situation , caused if not by faulty pump then a blockage ( air or sludge) either in the heat exchanger or pipework

, just had a thoughtthought, if your hot water is ok then it could be that youryour diverter valve is stuck on hot water and not switching over to heating. This would cause the situation you are having. I think they call the diverter valve the flow switch boiler

Customer: replied 3 years ago.

Thanks information I think I can hear the diverted switching over but could it still be stuck in water mode ??

Sorry scrap that , downloaded the manual . there isn't a diverter valve . the heat exchanger has a separate water way hot water and one heating . if the pumps ok , then you may have a blockage in the heating side of the heat exchanger .sorry mix up , I know it looks bad , should have checked the manual before now
Customer: replied 3 years ago.

Cheers ***** ***** been most helpful I will get new pump and go on from there tried turning cold water off to boiler to see if no water going to exchanger but no differant so not hot water side ?? Thanks

That's right . the heat exchanger has a pipe going through hot water to get heated and a pipe going through heating side on the same heat exchanger. Usually there are two the main one and a smaller secondary one water.
Customer: replied 3 years ago.

Will get new pump and go from there cheers ***** ***** your help can I contact you again when I get pump and fit it cheers

Ok all the best
Customer: replied 3 years ago.

Will give you a fantastic rating how do you do it

You got it sorted?
Customer: replied 3 years ago.

Not as yet nowhere in manchester open till tomorrow all the merchants close at 12 on saturday

Hope you got it going