STC-1000 with relays, wiring diagram?

[petrolSpice]

I'm pretty good with wiring DC electronics, but not AC. Does anyone have a wiring diagram for the STC-1000 with dual (heat and cool) relays? I would like to build up the controller unit to be able to safely handle 15-20A @ 110V, just in case I were to use it for other non-brewing related tasks.

Thanks!

 

[wilconrad]

I'd get 2 of these

Then connect pin 6 (for heating) from the STC-1000 to (+) pin on the input side of the relay. Ground the (-) pin on the input side. Then connect one pin on the output side to the line (hot) and the other output pin to the load (heater). Repeat with pin 8 from the STC for cooling, on the second relay.

This would increase the current capacity to 25A. Be sure to keep those SSRs cool, though.

 

[petrolSpice]

Wow, I didn't realize how large those are. Do all AC relays require a large heatsink? Do they only get hot if there is a lot of power flowing through them?

 

[wilconrad]

Solid State relays require a heatsink at higher loads, mechanical ones don't. If your application requires frequent switching, you want to go with the solid state relays. If you don't need it to switch frequently, you can use mechanical relays and avoid the heatsinks (mechanical relays wear out with frequent switching).

Edit: to answer your 2nd question, yes, SS relays only get hot at higher loads. According to Auber, the rule of thumb is that if the load is below 8A, you don't need a heatsink. However, if your load is below 8A, you can just use the STC-1000 and you don't need a relay at all!

 

[wilconrad]

So... thinking further about this, the STC has mechanical relays in it, so using SSRs wouldn't make sense anyway. I'll change my recommendation to these relays from Auber, they'll switch 30A (mechanically) and won't get hot. They're nice and small too.

 

[day_trippr]

I'm doing something similar. I have an STC-1K-like controller (an MH-1210, single stage) embedded in the lid of my new keezer, didn't want to run fat AC cables in and out of the lid, already had an AC feed for the interior lid light, so I'm running the controller on that feed and simply switching a remote relay to run the compressor, using the 12VDC I brought into the keezer interior to run all the fans to also power the relay coil.

Works a treat. Somewhat amazingly, the 10A relay inside the controller is way louder than the slaved 30A relay...

Cheers!

 

[petrolSpice]

Thanks for the tips on the relays! Now here is a dumb question... I bought an outlet for the unit that has a built in fuse which suggests using a 250V fuse. Lets says I put in a 10A 250V fuse. Is the limit of this fuse also 10A at 120V? Ignore the time to blow factor and other variables. Basically, is it the power (watts) or the current (A) that will blow the fuse?

 

[HopinJim]

Thanks for the tips on the relays! Now here is a dumb question... I bought an outlet for the unit that has a built in fuse which suggests using a 250V fuse. Lets says I put in a 10A 250V fuse. Is the limit of this fuse also 10A at 120V? Ignore the time to blow factor and other variables. Basically, is it the power (watts) or the current (A) that will blow the fuse?

Current is the driver here. 10 amps is the same to a fuse regardless of voltage. the 250V rating just means that it will withstand (and not arc thru) any possible voltage spikes from the 120VAC line due to switching on and off.