I'm not sure if the OP found his answer from this but I have a similar question and this is a fairly recent thread so here goes.
I've just made a temp control box out of a STC1000 and have it controlling a fridge. Fisher and Paykel fridge only (no freezer) which means I can stack 2 fermenters in it. It is working perfectly set at 22'C and yesterday I got to test it out on both heating and cooling. Really stable with settings of F1 @ 22'C, F2 @ 0.5'C, F3 and F4 default 3 minutes and no calibration. I've just got the probe in a 5 litre bucket of water to buffer against door opening etc.
My question is about using the fridge as a fridge for whatever reason, but mostly in the application of "Cold Crashing" once fermentation is complete. I've not done any cold crashing before and I'm not sure of the merits, if any, which is another question for somewhere else. Of course, I can just pull the plugs out of the control box and run the fridge direct to 240V, but I was thinking of including a switch in the control box circuit to break the Active power supply to terminals 5 and 7 of the STC1000 and divert directly to terminal 8. In doing this, the STC1000 would remain powered and still reading temperature from the probe, the heating element would become inoperative and the cooling controlled by the fridge thermostat, without needing to pull plugs. I can do it and think it will work as it would just be diverting the active with neutral and earth still connected. Has anybody done this or is there a problem with the STC1000 that I don't know about? I can't see anywhere that it has been done and I wonder why.
It should be possible with a standard 10 amp 240 V light switch to make / break the Active connections required. You can wire these to do two-way switching so they are mechanically suited to this application. With the temperature inside the fridge being below F1 the Heat circuit would switch to allow current but have no active feed. The Cool circuit would be off (open switch) but there would be live active at terminal 8. Would this cause damage to the unit? I can't see why it would.
I'd like to know your thoughts.
PS: The other option is to change F1 setting to 2.5'C but I think I would prefer to let the fridge thermostat control it in this instance.