I was looking at an antifrost fault on a MultiClima chiller today. (Just so you know why I had it open)
I don't get much practice on chillers in general, so wanted to ask a couple of general questions on parts of the fridge circuit itself:

a) What is the purpose of liquid injection (controlled by a solenoid valve) into the evaporator just after the TEV?

b) What is the purpose of hot gas 'by-pass' (controlled by a solenoid valve) straight back into the suction line?

This specific chiller has 2 x 3 cylinder recip compressors, 1 on each circuit; each compressor has 2 unloaders. It has 1 common plate evaporator with normal TEV's.

While I'm asking, I have also come across a slightly different setup on a Ciat chiller, where they have the discharge line tee off through a capacity valve and also into the evaporator just after the TEV. What's it for?

Thanks
Craig