Removing an unvented cylinder

[ArtfulBodger]

I am waiting to go on my Baxi CITB unvented course but in the meantime I have a job to do that I need some advice on.

I have to fit a combi to a 4th floor flat that currently has a challenger 30 system boiler hooked up to an old unvented cylinder. The owner wants the combi so the cylinder is coming out.

Up until now I haven't had to touch anything unvented and so would appreciate some advice here. First of all, as I am decommissioning only is it OK for me to do this without the CITB or equivelant ticket? Secondly, how do I do it? it looks straightforward enough - cut the cold feed and drain off as normal but am I missing something?

And lastly, call me a coward if you like but I'm a bit wary of working 40' up the side of a wall by a busy carpark!, so do any corgis have experience of flue fitting from the inside only? I can utilise the existing 4" hole but personally have always findihed off/weathered from outside.

Many thanks
AB

 

[bripl]

depends on boiler most manufactuers do a lnternal flue kit but you need a 125mm dia hole min. what about the safety release pipe? you could use the unvented s/r t/r pipe if it is suitable.as far as i am aware you do not require any bits of paper to remove unvented, but iam sure someone will know for sure.

 

[ArtfulBodger]

depends on boiler most manufactuers do a lnternal flue kit but you need a 125mm dia hole min. what about the safety release pipe? you could use the unvented s/r t/r pipe if it is suitable.as far as i am aware you do not require any bits of paper to remove unvented, but iam sure someone will know for sure.

Thanks for that, if it is 125mm minimum then I'm knackered as I'll never be able to use a core bit on an existing hole. I was planning on just sticking the PRV pipe straight through the wall with a few inches of overhang.

Guess I'll have to hire a hydraulic platform (and I don't like these either) then unless anyones got a beter idea

 

[PEDANTICVINDICTIVEMAN]

Why not drill a new hole next to the old one and use a 90deg bend straight of the top of the boiler, have someone outside in case core falls to outside, when I fit Worcester Cdi models they come with a black
weather seal that you fit to the end of the flue, then you push the 100mm flue through your 125mm hole then pull it back to seal, pump in some foam and hey presto, only use minimum foam as it will push through the rubber and dribble down the wall, so use sparingly.

As far as the discharge pipe is concerned the water will be cold and dipasitated by the times its dropped 40 ft, I would just drill through wall and poke pipe straight out,ooooooooorrrrrrrr, core drill a 35mm hole and feed a peice through the wall with two elbows soldered on ready.

 

[ArtfulBodger]

Cheers PVM, so you mean 2 90's to enable an offset next to the existing 117mm hole? what foam do you use? presumably it must be fire retardent

 

[PEDANTICVINDICTIVEMAN]

Yes, sorry not knowing what combi your fitting I took it for granted that it would have a 90deg elbow sraight off the top, which would normally go straight back through the wall, so yes using the normal elbow and facing it left or right then adding another one to go throught the wall you would be using two bends in total
I just use ordinary Builder Center foam, its not going to get very hot on the flue pipe as it's only touching the air tube and it's inside the brickwork plastered over on the inside.