Control window unit with SSR

[bcrawfo2]

I've bypassed my window unit's internal thermostat and want to mimic the thermostat function (which feeds the compressor) with a SSR, so I can control it thru my BCS.
My previous solution was to kill power to the AC unit when the fins iced up. This took forever unless I ran a bunch of fans. My idea was to keep the AC unit powered up so the fans run then kill power to the compressor.

I tried wiring a SSR in there and the compressor just doesn't like it. I don't know if the SSR output looks different than direct wired. I bypassed the SSR and the compressor works. Put the SSR back in....the compressor tries over and over to start up, but never does.

I'm trying to avoid a contactor, as my BCS can't drive that. I'd need BCS -> SSR -> Contactor.
The alternative is to put a heating element on the thermostat bulb and drive that element from the BCS, however that's going to introduce another layer.

Thoughts?

 

[day_trippr]

If the SCR source-drain On resistance is reasonable and it has sufficient current carrying capacity, the only thing left is your controller isn't fully turning it on...

Cheers!

 

[iijakii]

I tried wiring a SSR in there and the compressor just doesn't like it. I don't know if the SSR output looks different than direct wired. I bypassed the SSR and the compressor works. Put the SSR back in....the compressor tries over and over to start up, but never does.

You must be bypassing the start-up capacitor when you tried wiring the SSR in. They need that to provide enough amps to crank.

 

[bcrawfo2]

You must be bypassing the start-up capacitor when you tried wiring the SSR in. They need that to provide enough amps to crank.

I replaced the high side of the Ssr with a spst switch and it worked perfect. That tells me it has something to do with the ssr. Sri replaced the ssr with another one I had (both 40a) and get the same thing