Baxi 105e pressure problem

[quietman]

Hi guys/gals, my Baxi runs fine if cold set pressure is no more than 0.5bar, pressure increase when hot 1.5bar. If I try to increase the cold pressure to 0.7bar then the hot pressure reaches 3bar and the pressure relief valve drips the excess pressure away. When this happens and the boiler returns to cold the cold pressure is back to 0.5 bar and the boiler runs perfectly well.
So, I guess it's either the expansion vessel pressure needs topping up (boiler is approx 13yrs old) or the vessel has failed and needs changing. Any guesses as to which I'll find tomorrow when I press the shraeder valve?
Thanks for your help/comments.
Ps. Does a replacement vessel come pre-charged?

 

[mrStat]

Hi, yes a replacement vessel comes pre-charged. 50:50 as to whether or not it has totally failed. Just remember step to the side when you press that schraeder valve for when that water squirts out.

 

[Riley]

But you will require a gas safe engineer to fit it to your boiler as you should not be removing the cover legally as this can form a combustion seal that you have no way of testing if it’s refitted properly

 

[mrStat]

If it’s a standard efficiency 105e then the vessel is at the rear and won’t need access to the chamber.

Just remember. Don’t disturb the flue

 

[Riley]

So again a gas safe engineer is probably the way to go

 

[quietman]

Thank you guys for your comments. Fingers crossed that it's a top up required, the 0.5bar pressure when cold gives me a little hope although the replacement procedure doesn't look to much of a problem! I should have mentioned I am a City and Guilds trained Plumber and although I've been out of the trade for about 30yrs I've tried to keep abreast of the changes that have occurred. I believe, and I'm sure you'll correct me if I'm wrong, that the legislation requires a "competent person" in these circumstances so I would hope that I would qualify, after all I do have my own "U" gauge!

 

[Riley]

If you have to remove the flue you have no analyser to test its reassembly. I’m not being awkward if you need a new vessel fit an external one

 

[quietman]

Riley, you're not being awkward at all, I appreciate any advice. I've never fitted an external expansion vessel, if you have any suggestions regarding make I'd be happy to hear them. I believe it would be added like another rad to the system, I could site it next to the boiler. I think the current vessel is either 8ltr or 10ltr. Any input gratefully received. Cheers.

 

[Riley]

Just needs to be of a suitable size cut into the return pipework

 

[Riley]

I’d go to an independent merchant

 

[quietman]

I normally use my local Plumb Center. I thought the expansion vessel had to have a connection to both the flow and return?

 

[Riley]

It does, the boiler

 

[quietman]

Fair enough, I'm getting old but not too old to learn, it's just that the onboard vessel has a two pipe connection but as you say the system pressure is equal across the circuit. Thank you for your help.

 

[Riley]

Pleasure mate. We’re happy to help as long as no diy on gas appliances

 

[ShaunCorbs]

Normally fit them on the return but doesn't really matter

 

[quietman]

Update - I hate it when people ask for help on forums and don't let anyone know how things turned out, even for a relatively small issue like this. Anyway, there was still a little bit of pressure in the expansion vessel so opened a downstairs drain off to drop the system pressure to zero. Foot pumped the vessel to 0.7bar, book says 0.5 but not easy to get it accurate. Fill up, bleed rads, fire boiler, happy camper! Thanks again for taking the time to help.

 

[Rob Foster]

Thank you guys for your comments. Fingers crossed that it's a top up required, the 0.5bar pressure when cold gives me a little hope although the replacement procedure doesn't look to much of a problem! I should have mentioned I am a City and Guilds trained Plumber and although I've been out of the trade for about 30yrs I've tried to keep abreast of the changes that have occurred. I believe, and I'm sure you'll correct me if I'm wrong, that the legislation requires a "competent person" in these circumstances so I would hope that I would qualify, after all I do have my own "U" gauge!

Look at Top Up Mate , MFD from Flowflex Rob Foster aka centrakheatking