Combi Boiler Woes

[nwcharlie]

I have a combi boiler in a property that I moved into around 3 years ago. I would guess the boiler is 15-18 years old.
I currently have BG cover on the whole system, including pipework (4* I think). Every year I have it serviced.

When the system is cold, I aim to have 0.5 bar registering on the gauge. When the system is hot it goes to 2.5 bar. However, over the past few months, I seem to be topping the system up as when the system is cold it goes down to about 0.1/0.2 bar.

I am going to check if when the system is fired up, if there is any leakage from the expansion pipe outside. If it does, what can I do as the pressure in the system is the minimum it needs to work 0.5bar. If there are no leaks from this pipe, would I be right that there is leakage in the pipework somehwere?

If there would be a leak in the pipework, I am sure I would notice if was from upstairs as it would appear on the ceiling downstairs. Therefore, if a leak is present it would be from the downstairs pipework.

Would it be a good idea to get BG out to look at it, and if there is a leak in system, is there an easier way to find than ripping up my floorboards?

Many thanks

 

[kevplumb]

expansion vessel prob needs recharging see FAQ at the top of the forum

 

[electronicheat]

expansion vessel prob needs recharging see FAQ at the top of the forum

Or the diaphragm's gone kevplumb. It is quite a common fault on the oil fired system boilers I service. Just another thought!

 

[MANDATE]

I agree the expansion vessel is most likely to be the root cause of your problem.
If the pressure has ever reached 3bar the pressure relief valve will have operated. The problem then is when it closes again dirt gets trapped on the valve seat, so it never seals properly again.
If you tie a plastic bag over the end of the discharge pipe you can see what happens without any heating on.
So when dealing with the expansion vessel you really to to fit a new PRV.

 

[nickso]

So when dealing with the expansion vessel you really to to fit a new PRV.

or clean it.

just call BG out.

 

[MANDATE]

[quote="nickso";p="1410233".

or clean it.

easier said than done. How would a novice dismantle it?
I dismantled one today, after making a 'C' spanner

 

[bengasman]

Why don't you get it repaired foc under your 4 star service?

 

[nwcharlie]

BG is coming out to look on Friday, just curiousity to what could be happening thats all.

If there was leak in the system, is there an easier method than ripping up the floorboards?

 

[kevplumb]

any floorboards where their is pipework will have been up before