Sometimes it’s the simple things which cause the biggest headache.
When you get a call to a site because one of the boilers are only working intermittently, what’s the first thing you look for?
I know I checked; the boiler, the output of the controller.

So lets look at the simple things. I touched the output module plug the boiler started working!
Carrying out a bit more of an investigation, I found that the plug itself had a damaged lug and all of a sudden, the boiler started to work normally.
Success for a boiler which had not been working fully for quite some time.

Another success for the maintenance team!

Look at these two below. The first damaged belt was found on the supply AHU, so one checked the other main AHU and found the start of a fault.