To do a line clean do I need to turn off the cooler that the lines go through first?
Coolers should be turned off before a line clean, water has a higher freezing point than beer and could freeze the coil in the cooler. Doesn’t happen every-time but will do it when you least expect it to (Murphy’s Law). Then you will have to wait hours for it to thaw, so to be safe, best practice dictates switch the coolers off before a line clean. This also improves the performance of the line cleaner solution.