So......

One for the techno guys here, I have jumped in at the deep end like usual and convinced someone a PLC Relay is the way to go to solve the issue they are having with their heating system....

No BMS Control, so the twin set pump is running constantly with pump 1 as the "master". Pump 2 never runs until pump 1 fails, and by that time it hasnt ran for so long it is also ****ed.

So, Ive always wanted to learn PLC stuff as I like a challenge.

So quote accepted, PLC and associated relays ordered. Now Im well and truly in the deep end of the proverbial pool and need to programme it. I have written up something but no idea if it is right (Its essentially drawing my cct on the computer from what I can gather).

However, I cannot for the life of me figure out how to run my common fault light. I want the light to illuminate on the failure of flow.... Each pump however has its own pressure switch. There is no room or tappings on the pump to allow me to fit an external pressure switch.

This is what I have so far -




I am having a bit of brain meltdown at the moment and am sure I have missed something obvious with the common fault light, im just not sure what yet!

Any input?