The task is simple or so it seems.

The call out was placed and a report from the previous mechanical maintenance engineer stated “The Hot Water Has Stopped Working”.

Being a BMS Engineer, one knows it can’t be a just a fuse, so where do I start?

Upload the controller strategy, hunt for the non-existent wiring diagrams and find that the panel has been modified anyway with no recorded documentation

I play with the switch on the front of the panel. The light is ON so surely it should work.

The controller says it should be on…hmmm
The contactor energises fine.
I have measured power at the primary side of the contactor…and the outgoing terminals…alright
Now where’s the HWS Tank?

Okay we have power there too…

Lets strip it down…I know, not my department…but taps are cold…

Ohhh there’s a relay just hanging loose; what’s that doing??
Ahh and power on only one side…must be that…now where’s the manual?….hmmm

Time to look up a datasheet on the internet on the phone to download the manual….turns out that the relay has been wired as a fault relay…

Lets go back to the panel and start at the beginning…..check emergency stop….gas valve….fire alarm…fire link above boiler…boiler fault….high temperature stat…. all okay!

Must be the controls!
Back and forwards we go until my Fitbit says I have now run a marathon.

Then I spy it on top of the boiler; is that a button I can press? Ooohh and it has a temperature sensor attached to it. possibly a high limit stat? Press it…that feels good…hang on I hear ignition…

Hurrah we have temperature, now let’s write a report whilst I wait for the temperature to rise. But what do I put in it?
…this wally couldn’t find a switch?
Now what have I learned?
Sometimes check the obvious. But what will I do next time??