Combi Boiler Pressure Too High *When On*

[mcompton69]

We were lucky enough to inherit a Worcester boiler with our house (28i Junior to be precise). Never had a problem with it, or the CH system.

Bled a top of house radiator sunday night as the top wasnt hot, no probs there, didnt check the boiler pressure afterwards though, and Monday morning the missus had hold/cold shower as the boiler didnt work properly due to low pressure (the noise of the air in system woke me up).

So carefully topped up the system to 1 bar, no problems. Came home from work 9 hours later, same pressure of 1 bar (so i dont think the mains valve is open at all).

However, when the system is on the pressure rises to 3 bar (when it red lines), i dont recall it ever getting that high before when running.

Q1) Should I be concerned about this? Do i need to do anything?
Q2) Could it cause damage to the boiler?

I mention the boiler make/model as i am sure that there will be a pressure release valve, and i can see a plastic pipe leading to the shower waste water pipe, so it shouldn't explode! But I want to make sure...

Thanks for any advice and tips people, you could save me a significant plumber call out charge with your advice!

 

[compheat]

Sounds like the expansion vessel (at rear of boiler ) as lost pressure, the reason it wasn't a problem before you topped it up and let the air out of the top radiator is that the rad was say half full and any expansion was taken up in the radiator.

 

[easyflow]

I would look towards the expansion vessel, may need re-pressurisng or may be faulty.

 

[neiltheplumber]

As above!

 

[Slugbabydotcom]

Probably be cheaper to add another vessel to the system if you have the room for it. It will be about the size of a basketball and need plumbing in to the return

 

[Terry lambert]

Only replace if the existing is faulty, normally they can just be serviced.

On larger properties the vessel in the boiler isn't really big enough, and so fit a second vessel to the system to allow for the extra expansion.

Your engineer should be able to advise if this is nessacary