Commercial boiler trouble

[keh7486]

Hi got to go to a building Monday because of a boiler/extractor problem.
What I have been told is this
3 phase boiler
3 phase extractor fan
Pressure switch either side of the fan


Apparently when you isolate fan the boiler doesn't turn off and the same when the pressure drops from pressure switch the boiler stays on.


My question is how should this be wired and where do I start. Any help would be appreciated as I'm dreading this job.

 

[HandySparks]

So which of these two identical threads would you like answers on?

Don't do it; it just annoys.