Gary - the last two plates freeze to their design spec and the system is turned off manually when it is ready, if you add a little gas it starts to freeze back to compressor, its not a controlled system its run by feel the and stop the timer thats why it has never got back to the compressor (yet).

The bulb is not insulated but taped on with metal film (think cling film made of metal) and system has a sightglass which is pure liquid at all times. A quick guess at the SC is 2 to 4 dergrees but I am away at the moment and dont have the data to hand.

There are many points I have read and would like to discuss but for a few days the big cyclone is taking up many peoples attention.

I still think its running from a nearly fixed temp in the freezer acting on the diaphragm and the pressure changes are just small changes to orifice size - not control but just change.

Chef