Fermentation chamber (temperature controlling fridge)

Forgive me if this question has been asked before. I've been able to find threads that partly answer my question but this the equipment I have or is in transit. Would be greatful for any advice and suggestions for my setup, which is as follows:

I'd like to ask people with authority/knowledge in this which solution is "preferable" from safety perspective when using the fridge as a fermentation chamber running more or less "unattended" for a complete duration of 2-4 weeks.

The fridge is in my kitchen - so safety is number one for me!

Firstly the fridge is of a recent model, so from this forum I gather it should have "a snubber circuit" already built into it.

Secondly the kitchen isn't heated which means in winter times it gets VERY cold in there. So to maintain higher temperatures in the fridge (18C/64F) I have a 100W aquarium heater with a built in thermostat. I'd like to control this with the Arduino as well.

Now for the power switching circuits I have considered/purchased:

The STC-1000 is a VERY popular $10 (off eBay) item to control the compressor and a heat exchanger to control the temperature inside the fridge but the relays are only rated at 10A. The saying goes you get what you pay for and a cheap Chinese relay rated at "supposedly" 10As and $10 doesn't sound safe to me. I've regretted buying this.

Instead I turned to a Powerswitch tail NC kit which is rated at a more confident inspiring 40A using a AZ21501-1A-120AE electromechanical relay. Details are available here http://www.powerswitchtail.com/Pages/PowerSwitchTail240vackit.aspx

I also have a set of Crydom HD4825 relays on a chunky heat sink on the way. These are rated to 20A. Unfortunately I don't know much about SSRs and this forum has some threads circling around zero switching and what not, but I've been unable to grasp whether zero switching is desirable or not to run the compressor on the fridge.

If you are simply turning the load on and off (not phase control), you don't need zero crossing.

The compressor on most fridges are not designed to be driven by phase control, they are simply off or on for a period of time.

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