Boiler not working after replacing expansion vessel

[Yanni]

I've got a Worcester 25si combi boiler.
I've just replaced the expansion vessel as it was making loads of banging noises and on inspection it was faulty.

Now, after putting everything back, the boiler only works when the heat exchange cover is removed. If I place it back then the spark electrodes keep on going but no flame !.

What am I doing wrong ? I've also noticed the fan got a bit noiser after re-assembly.

 

[swbjackson]

Time to call in a professional by the sound of it. You've already caused damage changing the expansion vessel and you're now looking at combustion faults.

Mike

 

[LUNAT]

HI

have you disturbed the air pressure switch ?

 

[DP]

That is a new one- expansion vessel causing banging. Must remember this one.

OP, do you know what the function of expansion vessel is?

 

[Yanni]

The boiler now works fine with the new vessel fitted.

The banging was with the old EV as the diaphragm had failed !

All I've had to do was to put the second inner cover on and it fired up great.
It has three covers, the outer white one, a first big inner one that covers the heat exchanger, combustion chamber and fan, and a smaller third inner one that only covers the combustion chamber and heat exhanger.

I was trying to get it going with only the small inner case in with no success.

Now final question, as it has been long since the boiler worked fine, when I get all the radiators on full in the house( five of them ) the pressure on the boiler goes from 1 bar to 1.9.

Is this normal or should it stay similar whether on or off. I did pressurise the expansion vessel to 0.5bar as per manual after I had drained the boiler. I did also bleed all the radiators. I'm wondering if I would put 1bar pressure on the expansion vessel, would the pressure during operation pretty much stay the same as when the boiler is cold ?

 

[bengasman]

you need to get a RGI to check your boiler asap because you have been fiddling with things that you don't understand which leaves a potentially very dangerous situation.

 

[Yanni]

Answer to my question please ?

Thanks...

 

[bengasman]

the answer to your question is:
what you are doing wrong is taking on something above your capacity and thereby endangering yourself, your property, your family and your neighbours.

 

[sloppytom]

you could have damaged the ignition leads, so it just earths on the cover when its on. usually 1 bar when cold then upto 2 bar when hot

 

[jamesdean]

Now final question, as it has been long since the boiler worked fine, when I get all the radiators on full in the house( five of them ) the pressure on the boiler goes from 1 bar to 1.9.

Is this normal or should it stay similar whether on or off.

It`s quite normal for the pressure guage to rise from 1bar when cold to 1.9 when hot, it`s all down to the water expanding as it heats up, nothing to worry about.

 

[andytheplumber]

sounds like possitive and negative pressure problems.