[cdowns]

Is the relay for your heater controlling the main voltage input or is it controlling at the thermostat connection?

I've been wanting to do something similar with the units in my apartment (they're similar to what you'd see in a hotel window unit). The thermostat and controls are integrated and I can't disassemble to access them, so I either need to build a rig to push the buttons (hard) and turn the temperature dial or just put a relay at the mains and manually set them for AC\Heat depending on season. Adding a relay to the mains seems straightforward, but it's 220v and I don't want to mess up.

[deepsy]

The relay is controlling the main voltage input and it's similar to http://i.ebayimg.com/00/s/NTAwWDUwMA==/z/ZS0AAOSwr81UNgc9/$_.... The relay's function is to act like a central switch. I have also a servo attached to the thermostat and it's only role is to spin the thermostat controller. The servo is similar to http://www.conrad.com/medias/global/ce/2000_2999/2000/2060/2...

[anfractuosity]

You could also look at SSRs, which tend to be easily controllable with logic level outputs on a microcontroller.

[Freak_NL]

Solid State Relays (SSR) do work great. Internally they use an LED to close the switch rather than the mechanical coil mechanism used in the classic click relays; these are totally silent.

I am using one to turn on/off the mains power of a 12VDC transformer. The nice thing about an SSR with an input range of 3–30V (a common type) is that you can drive it directly (and safely!) from a Raspberry Pi GPIO pin (3.3V).

[deepsy]

Thanks! Will definitely look into them :)

[cdowns]

Thanks!