puma 80e low pressure problem

[mrt]

I have Puma 80e boiler servising 10 average size radiators. It is loosing pressure after heating is on. Pressure rises from 1bar(cold) to over 3bar (hot) in several minutes then pressure valve opens and system pressure reduces below 0.5 bar when cool down. By now i have changed both the pressure release valve and expension vessel but problem is still there. Can it be faulty pump ? Many thanks in advance

 

[mrt]

I forgot to mention. there is no leeks. Pressure when cold does not change for days

 

[croydoncorgi]

Yup.
or the hot water flow switch stuck,
or an airlock in the heat exchanger,
or a blockage in the flexi leading to the expansion vessel (you did check that when you changed the vessel...?) ,
or...
It's EXPENSIVE to fix boilers by random part-changing.
Sorry to be brutal - but it needs experience and knowledge.

 

[kevplumb]

did you change the flexi pipe that connects the ex vessel

 

[mrt]

Thanks for your help
I could nor agree more i should call professional but I just had bad experience. I was charged 100£ to charge the pressure valve - it did not help so i was told to change the expansion vessel will cost me ~450-500£ and 5 hours labour !!!! I did it in 30 mins just following the manual(there is plenty of space around the boiler)

Unfortunately I did not check the flexi pipe for the blockage. Is it common ? Does it have to blocked completely for pressure to rise?
This is 10 litre expansion vessel. Is it big enough for the 10 radiators CH system ? How can i check that pump is operating properly ?

once again many thanks in advance

 

[bogstandard]

Should be fine for 10 average rads
The flexi pipe would have to be considerably blocked
but then as Croydoncorgi mentions mabee the hot water flow switch stuck.
I would not have thought the pressure overflow valve would have been the first part to change as the pressure was showing high.
Does it work with the hot water?

 

[mrt]

First of all thanks to everybody contributed. It was a blocked flexi pipe!!!
It was comletely blocked !!!! I unblocked it and pressure does not increase higher then 1.5bar (1.2 cold)
After bad expirience with local plumber (he changed the valve and asked 500£ to change the vessel) I thought that being experimental nuclear physiscist would be good enough to sort out the CH. I was wrong !!! Nothing can substitute the expirience. During my pluming adventure I bought Exp.vessel. What is a return policy of the UK distributers? I geuss I staked with it as I already fitted it in ?

 

[bogstandard]

I sympathise with you - finding a good Heat eng is very difficult and being Corgi Reged is of course all too often completely meaningless! Now I'm looking for a dentist!!! Fortunately there are some excellent lads on here. I rather doubt if you can return the vessel - particulaly as I doubt that you have a trade account! Write it off to a learning experience and I am sure it was ultimately cheaper than getting someone in once again.

 

[croydoncorgi]

If there's black crud in the boiler, then there's almost-certainly no corrosion inhibitor in the system. Pity, because some blockage of other parts (eg. 2ndary heat exchanger will probably have already occurred.

Try putting some Fernox System Restorer in the system for a week or so, then flush it thoroughly (several complete fill / empty cycles particularly making sure that boiler air vent is working and the boiler gets a good rinse. Then refill and put in some inhibitor, and keep fingers crossed. If you get a fall-off in HW performance and / or rads only getting hot at the top, then it's power-flush time.