Puma 80 - Keeps blowing off the CH water!!

[pic_whizz]

Hi there,

Firstly what happens:-

1.my sister comes home from work and switches on CH.
2.Water kettles up and then dumps the CH water out the PRV.
3.Low pressure LED on as you would expect.

Jobs already completed on the boiler:-

1.Re-pressurised the CH Expansion vessel to 15psi.
2.Replaced CH water pressure swicth (Old switch destroyed last time the water was dumped!)
3.Replaced PRV.
4.Replaced DHW flow Switch.

Possible fault now causing this (my ideas!):-
1. Pump impeller damaged/intermittent rotation from cold
2. Blockage somewhere
3. Wax diverter valve faulty (sticking in Hot Water mode)

Other notes:-
1. Boiler has been working fine for over a week.

I have not seen the fault occur as it only seems to happen when the boiler has been switched off all day and then re-lit at tea time.

Does anyone know what else goes wrong in this common boiler??

Please help! I'm losing my hair with this!!

Thanks,

Matt

 

[kevplumb]

are you sure the vessel is not full of water ie diaphram punctured
are you sure the pipe to the expansion vessel isnt blocked

 

[pic_whizz]

Hi kev,

Cheers for the reply.

Have checked that air came out of the vessel - so I assume it's ok. Also checked the pressure using tyre pressure gauge to make sure it hasn't dropped - it's still around 15psi.

As to the pipe connecting the expansion vessel I haven't checked that yet - do they sometimes block?

Cheers for the help,

Matt

 

[kevplumb]

yes theres another post with the same prob
has to be worth checking

 

[ChrisR]

I hope you've pumped up, and measured the pressure in, the exp vessel with absolutely no pressure on the system. Lots of people do it wrong at first. When you pump it up, you can get the prv to stay open, then you can tell it's pushing water out as you pump. If it does do that you know the exp vessel connector pipe is clear.

You could take the head off the pump an see if the impeller vanes are clear and not full of sludge.

As it's intermittent- something sticking - like the diverter, sounds likely.

 

[pic_whizz]

Cheers guys,

Good couple of things for me to check now. I must say I didn't check if water was pushed out the PRV when pumping up the Expansion Vessel,although I did leave the PRV in the open postition whilst pumping it!

I'll try it tomorrow and report back.

Thanks once again,

Matt