[avidiax]

This sounds good, except that cooling a box is problematic. He needs the temperature sensor to read low so that it turns on the heat.

That said, if he has access to the interior of the thermostat, I'm sure it won't be difficult to replace the temperature sensor with a circuit to cause it to read either really high or really low on demand.

[dtech]

For such a minor use case a peltier element is suitable. Very energy inefficiënt but you don't need much and it can both heat and cool.

[willvarfar]

I was literally imagining duck-taping one of those cheap electric "instant cooling" cups over the box on the wall, and running a small incandescent bulb in to be the heating up element.

[toast0]

> This sounds good, except that cooling a box is problematic. He needs the temperature sensor to read low so that it turns on the heat.

Ice pack and desiccant?