Baxi 105e - I need a new expansion vessel

grumpycrab

Hi - been told that our "expansion vessel" needs replacing (don't understand the technicalites but its full of water? should have some air in it?).

This doesn't appear to cause any major problems but the result is that the boiler over-pressures. In fact just seen it at 5bar (don't laugh - yep the needle was all the way around, plus a bit more!). Pressure was reduced by running a hot tap for a few seconds. I guess this could get bad if I don't do something about it). Have been relying on the pressure relief valve to vent water...

Been quoted £300/£400 all-in to fix this (boiler off the wall job). Its 10 years old and I guess this is much cheaper than getting a new boiler. Do you agree?

ariba10

Get a second opinion. They can be repressurized with a car foot pump.

happybiker

It will cause you major problems if you don't get it attended to. Your pressure relief valve should operate at round the 3 bar mark and running hot water shouldn't make any difference as the DHW side of the system is separate from the pressurised ch side. If running hot water does make a difference, then there is something more serious happening with your system, than a faulty expansion vessel.

As to the expansion vessel itself. If there is a convenient spot on the system , a separate vessel could be fitted without having to disturb your boiler.

I think I would get a second opinion and a thorough examination of the boiler before going any further.

grumpycrab

Thanks guys. Yes, the 5bar was what panicked me - it was definately 5bar! - should have looked at the water outlet. Perhaps (just maybe) the CH had come on when I drew off some hot water. This is the 2nd chap (different company) who said it was the vessel.

Will get somebody in ASAP.

unclebulgaria

Does this boiler only go over pressure when the CH is on or does it creep up when the heating is cold?
If it goes up during CH operation its more than likely its the expansion vessel diaphragm split and its no longer balancing the CH pressure properly.
If its going up when the heating is off and cold it could be a split in the plate heat exchanger (the hot water bit) and its allowing cold mains pressure to pressurize the CH system.

There is always water in one half of the expansion vessel and the other from new is Nitrogen gas, if the diaphragm splits then the only thing is to replace it. There is the option to fit an external one which may work out cheaper so long as the existing expansion isn't leaking water?

The other thing it could be is a blocked pipe feeding the expansion vessel.

grumpycrab

Thanks. Not sure what brought the pressure down from 5 -> 1 bar (it was either me running hot water or CH coming on) earlier this afternoon. Pressure certainly appears to build when cold.

This evening (with CH on) the pressure is also slowly building. Currently at 2bar.

A very small leak has developed within the last couple of weeks.

An independent is going to quote me for plate heat exchanger and external fitting of expansion vessel (assuming that can be done without leaving any leaks). Will also quote me for a new Worcester-Bosch (with 7 year warranty!?).

garethgas

Happy biker is right.
The expansion vessel thats integral to the boiler can be left alone and an external one fitted if there's a convenient space nearby.
As you've been using the pressure relief valve it would be a good idea to replace that at the same time as they often don't re seat properly
It won't cost you £400 either :beer:

rustyboy21

Baxi do offer an out of warranty repair service, which will include all parts and labour, no matter what it is, I believe.

They seem to arrange callout quick too, if me ringing through to have an in warranty fire sorted out, which come back as 10 days, but a customer with an out of warranty one paying for callout getting quoted next day !

Heard it works out cheaper than getting your own engineer to get parts for you.

Check and see how much it will cost, but don't tell them it could be the expansion vessel, say pressure keeps going into the red.

Just a thought

grumpycrab

After the "5bar incident" boiler pressure appears ok today. Running between 1.5 and 2bar (CH off during the day and with CH on for an hour tonight). Chap comes Friday.

gas4you

ariba10 wrote: »

Get a second opinion. They can be repressurized with a car foot pump.

Not when water comes out of them.

Cheaper option is to fit an external expansion vessel, as close as possible to the boiler.

ariba10

gas4you wrote: »

Not when water comes out of them.

Cheaper option is to fit an external expansion vessel, as close as possible to the boiler.

Where does it say the water was comming out of it?

I still recomend a second opinion.