Can you help me please ?


I have a problem with my Potterton Puma 80 combi-boiler. ( permanent pilot model )

When I use it for hot water only ( with central heating switched-off ), the boiler works just fine. No problems of any kind.


But.....


When I switch the central heating on, two types of problems occur :-

1. If the central heating stays on for more than 2 hours continously ( at night for example ), the system pressure gradually climbs-up from 1 Bar to 3 Bars and above, which causes the pressure release valve to open, and this in turn drops the system pressure right down to Zero Bars, which in turn turns-off the boiler due to low system pressure. If I then top-up the pressure back to 1 Bar and switch the central heating back on, the above cycle repeats itself on and on.... Basically when I'm using the central heating, the system pressure refuses to stabilise itself within its normal parameters, i.e. between 1 Bar and 2 Bars.

2. the second problem, which also occurs only when the central heating is switched on, is if I run the hot water continously for more than 10 minutes, the pilot light goes out. If I turn it back on, once again, after running the hot water for more tham 10 minutes, the pilot light goes out, and so on.....

Both problems only occur during the winter months when I'm using the central heating.

In the summer months, when only hot water is being used, neither one of these problems occur. The boiler works perfectly then.

I have replaced the electronic boards, but it didn't help.

Greg, December 2008

Thanks Arthur,

I have pushed-down the pin as you suggested and only pure air came out. I have then drained the system and re-pressurised the vessel with an air-pump to about 1 Bar.

However, when I re-started the central heating, within 2 hours the pressure climbed up to 3 Bars and the system automatically drained down to zero. So the same problem as before...... Any ideas ?

Thanks

Greg, December 2008

the pressure vessel it has a small air valve on it

arthur, December 2008

I am having similar problems with a Puma 80. In my case I replaced the pressure release valve as this was the cause of pressure loss and leak from the boiler, however I also replaced the automatic pressure valve due to water escaping from the top when pressed. I still have pressure gain when running central heating. Arthur you mentioned pressurising the unit with a pump, which unit are you referring?

Robert, December 2008

the fault is on the pressure vessel it may need recharging undo the cap and push down the pin if water leaks out a new vessel is needed if air comes out it just needs blowing up with air bike pump would do it drain boiler to recharge about 1.5 mbar

arthur, December 2008