STC-1000 questions. Be gentle =]

[TANSTAAFB]

I finally wired up the STC I had lying around with the idea that I could control the 1000w heatstick I have to pre heat strike water or hold temps for a kettle sour. I used a fused power receptacle (like for a computer cord) with an LED rocker switch. Took a bit to track down the fuse (I picked up a 10 amp slow blow and a 15 amp fast blow...insert that's what she said joke here) but finally got everything going, started a test with the heatstick, and about 20 minutes in noticed smoke and shut it down. I think the smoke was coming from the fused, switched, power cord receptacle. I used another computer power cord as the donor for the wire thinking the gauge would be sufficient. So, what went wrong? I know Jack Schitt about electricity but I can follow a wiring diagram.

 

[FunkedOut]

so the smoke was coming out of the project box for sure?
what gauge were the wires you used between the STC and the outlets it powers?
what gauge were the wires you used between the STC and the outlet it gets power from?
what is the rating on that switch you used for the outlet?
any chance you have a short in there?
open it up and look for black spots or melted jacket where the smoke was coming from.

 

[TANSTAAFB]

Definitely saw smoke when I unplugged it. Immediately removed the screws but could not tell where it was coming g from. It looked like it was from the power cord receptacle side. That receptacle is fused with 250v bus fuse and a 10amp slow blow fuse in there. I just checked the gauge of the power cord that I chopped up to get the wire and it's 18awg which should be good for 10amps.

 

[TANSTAAFB]

The intact power cord is also 18awg from the controller to the wall

 

[Blazinlow86]

Are you sure you didn't smoke the relay in the stc1000. I don't think it can handle the load of a heatstick without a additional better relay?

 

[FunkedOut]

So what’s the rating on the switch?
These are 15A outlets right?
How about a pic of the wiring?

Maybe the project box is in contact with a wire it terminal that got hot and melted some plastic?
That would be self clearancing as long as it does catch fire.
How did you mount those?

 

[TANSTAAFB]

I'm traveling and didn't have a chance to get pics of the guts. I'll do it when I get back and post it up. I also realized that I just wrapped the wires to the contacts on the switch as I intended to solder them and have not yet. That could be a bad connection or short somewhere

 

[Goblism]

18 awg is not enough for 1000 watt, especially for prolonged use. 18 awg is rated to 7 amp, or 840 watts. Suggestion is usually 80% of max for continuous use, or max or 672 watts

 

[kristiismean]

get a RIB

https://tinyurl.com/ya5grjse

 

[TANSTAAFB]

18 awg is not enough for 1000 watt, especially for prolonged use. 18 awg is rated to 7 amp, or 840 watts. Suggestion is usually 80% of max for continuous use, or max or 672 watts

Thanks, I'll rewire with a bigger gauge. I really thought those power cords were 16 at least. That's what I get for assuming!

What gauge should I use?

 

[TANSTAAFB]

get a RIB

https://tinyurl.com/ya5grjse

What's that do and how do I use it? I was a plumber, I'm electrical impaired [emoji6]

 

[kristiismean]

it's a Relay (Relay in a Box = RIB). Instead of your STC1000 making the connection and having 1000 watts go through it, it will route that 1000 watts through the relay, which is good up to 20 amps and the STC1000 will only see a very minimal amp draw (less than an amp).

this relieves almost all the stress off the STC1000 and places it where it's designed to take it, the relay.

 

[TANSTAAFB]

it's a Relay (Relay in a Box = RIB). Instead of your STC1000 making the connection and having 1000 watts go through it, it will route that 1000 watts through the relay, which is good up to 20 amps and the STC1000 will only see a very minimal amp draw (less than an amp).

this relieves almost all the stress off the STC1000 and places it where it's designed to take it, the relay.

Sweet! How would I wire it in? I followed the basic wiring diagram that's out there for 2 sockets and added the power cord receptacle and switch

 

[kristiismean]

I'll send that tonight. it's pretty easy. I use this setup on my inkbird stc1000 thing (same as yours) for my kegerator

 

[FunkedOut]

1000W heat stick at ~110V draws ~9A.
7A is a good limit for 18ga if you do not have good cooling circulation, like two insulated wires inside an outer jacket.
I bet there is no ventilation for your project box either.
16ga should work just fine, but 14ga primary wire is dirt cheap and gives you an added margin of safety.
I don't think you'll save much buying a roll of 16ga over a roll of 14ga.

Regarding the relay, there's nothing wrong with using it, but the STC has relays. It's a product that consists of a controller and a pair of relays. The relays in the STC are rated for 10A. No reason to get higher rated relays, IMO.
Keeping the wear on the STC down is not much of a concern either. A new STC is cheaper than that RIB.

 

[kristiismean]

he does has a point, a new STC is cheaper than the rib,

the wiring is easy, mines all together so it would be a pita.

I am hoping by using the RIB, my stc never fails...

 

[TANSTAAFB]

Very true, they're cheap! But I'll upgrade the wiring and make sure I use spade connectors or solder

 

[doug293cz]

I think your problem is the wrapped connections on the switch. These are likely to be high resistance, which will cause them to overheat. 18AWG should work for 10A, but is marginal (but shouldn't smoke unless you coil it up.) Just as a point of reference, the wire gauge used in the InkBird ITC-308 (rated for 10A) is the much closer to 18AWG than 16AWG (it's a metric size, which I don't remember off the top of my head, just remember it is finer than I expected it to be.)

Brew on