This part of the circuit may be in relation to refrigeration or cooling in general.
I've been asked to evaluate this circuit but I don't know what IL1 is.
I assume BS21 is a switch, switching possibly temperature probes.
But I'm confused in general. Can anybody help.
BS21 is a manual rotary switch based on the symbol. IL1, I would guess a temperature switch or controller of some sort. The rectangle plus the dashed line to the adjacent normally open contacts suggest a relay, with the rectangle being the coil, but in this case it probably represents power supply connections to that device. The diagonal line with the horizontal segment is similar to an NTC, and the output apparently controlling a compressor certainly suggests temperature control. The 'A B C' and 'D E F' blocks I guess would be control inputs, so that would fit with your suggestion that BS21 is switching temperature probes.
There are a handful of different styles/standards for symbols in wiring diagrams like this, plus sometimes people just make things up when there isn't a a suitable standard symbol. Sometimes it helps to take a guess and do an image search for '____ wiring symbol' or similar and see if anything looks like a match. Or sometimes you just have to trace out the device (those numbered connections can be a big help, if the wires are actually labeled), and see what the thing physically looks like
Many thanks for the reply. The machine is long since gone. It never really worked but now that are trying to propose an new one.
I'm not familiar with single wire temperature probes but I suppose that could be two, twin wire probes being switched. It's not usual to switch probes either with a relay.
They have another machine with a three wire Ice Probe and controller. See attached.
So I'll have to assume something similar was going on here.
Thanks again.