My Ravenheat CSI primary condensing boiler will not fire up. I called out a heating engineer who diagnosed a faulty air pressure switch. He fitted a new one but still no joy (another £100 quid down the drain). He then said the fan was "inefficient" ? And would have to be changed at a cost of £200. Lo and behold that did not work either, however when he blew into the tube feeding the air pressure switch the boiler fired up but cut out again when he stopped blowing. He then said he would go away and discuss with technical people. He has not been heard of since. This was the most expensive blow job i have heard of !!!!!!!!. Any advice apart from ripping it off the wall would be greatly appreciated. Other engineers don't want to get involved.

Perplexed, August 2017

Im amazed you paid him to fit parts that didnt solve the problem

Lets look at this problem logically

The CSI range has a combustion casing front cover held on by approx 13 screws which have to form an airtight seal in order to create a negative pressure inside the depression chamber so that the fan can activate the air pressure switch and start the ignition sequence

In simple english
Air tight cover -> fan -> aps -> boiler ignites

The guy you had out has already proved the aps works
By sucking on aps tube

If fan still rotates fast enough to activate aps & isnt sluggish
I would have to assume the depression chamber is defective in some way
ie no airtight seal

The depression chamber is constructed of pressed sheet metal & spot welded on the joints
These spot welded joints are known to fail after a while

Also the self tapping screws holding the front combustion casing cover may fail to grip securely (due to oversized holes in the sheet metal) & fail to create an airtight seal

There are ways of testing the airtightness of the depression chamber using a smoke bomb & a plastic bag over the flue creating a bellow effect & seeing where smoke emanates from failed joints

My guess is most gas engineers wont do this test as it is laborious & even if you do find a joint failure on the depression chamber the only solution is either depression chamber replacement (an absolute nightmare of a job) or more realistically a boiler replacement

If you are determined to keep this boiler i would recommend you contact ravenheat directly who could probably recommend a ravenheat repair specialist in your area

Asbestos, August 2017

Some similar threads here:

http://www.ukplumbersforums.co.uk/threads/help-please-with-ravenheat-csi-85.34324/

http://community.screwfix.com/threads/ravenheat-problems.65241/

http://npht.forumotion.net/t5-ravenheat-sequence-of-operation

https://www.justanswer.com/uk-plumbing/783mi-ignition-problem-ravenheat-csi-primary-condensing.html

acp, August 2017