Electrical Gurus - Temp Controller Question

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uatuba

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I want to replace the thermostat on my upright freezer with a digital controller, but I'm not sure from the diagram how to wire it. I know, for example, that if I use the STC-1000, I have to switch the hot leg. However, on the diagram posted, I'm unsure if there is a neutral at the thermostat or if it is a switched hot--which would make the most sense.

Long story short, how do I need to wire a digital temp controller using the wiring at the thermostat. Do I need to run a neutral to where the thermostat is? Any help is appreciated. Normally I can figure this stuff out, but I've had a few home brews and I'm in the mood to order what I need.

ImageUploadedByTapatalk1392611578.094189.jpg
 
I agree with Bru, I looked at the picture about an hour ago. I could see the diagram but couldn't see it well enough to interpret it correctly.
 
I just did this to a chest freezer. the STI1000 is essentially just a switch. it provides no power to the freezer.

so, what I did was to expose the wires on the main power lead about a foot from the main plug, I cut the active wire (brown in Aus), and wired a female plug end to it (ie, so shorting the two sides of the female plug would act like a switch). then I cut the female end off an extension lead, and wired the active and neural to the cooling side of the STI. Polarity doesnt matter, its just acting as a switch. Plug the male end of the extension cord into the new female end on the freezer, and you now have the switch on the STI able to turn the freezer on and off. Plug the freezer in as normal, and it works perfectly. I didnt take any photos, but I could try if you need some visual cues.
 
Not sure why it's posting out of focus...it's clear on my phone. Let me try again:

ImageUploadedByTapatalk1392639264.179939.jpg
 
They were hoping for a tighter shot.

At the top of the diagram is the thermostat, with a hot side connection on the left and switched connection on the right. Disconnect those from the thermostat, connect the hot side to one side of the Cooling relay on the STC-1000 and to the line input as well. Connect the switched connection to the other side of the Cooling relay. Then add a neutral wire between the other Line input connection at the STC-1000 and the line cord neutral ("cut and nut" will work)...

Cheers!
 
Thanks! You're right...and now that I'm in a...um...clearer state of mind, it's really obvious what they're going for.
 
I think, to save some trouble, I'm going to use the ground that's already run to the thermostat cutout as a neutral...just wire it in at the plug (if I can find where it terminates...shouldn't be too difficult). I'm pretty sure it doesn't straight from the plug.
 
Please don't tie safety grounds to neutral current returns.

That's really bad juju - and not just to someone who should be dead because of an electrician's error on a 25KVA three phase drop laying under a computer room raised floor. But I digress...

You can simply cut the white wire from the line cord, strip the two ends, add your neutral wire for the STC-1000, and use a wire nut to twist it all together.

Besides, you'd never be able to plug the controller into a GFI outlet without it instantly tripping if you tie the current return to safety ground...

Cheers!
 
You're not getting what I'm saying...there is a ground running from a ground bar near the compressor to the thermostat. I'm going to unhook BOTH ends and use the insulated ground as a neutral. It will not function as a ground and will not tie ground to neutral--it simply removes the ground from the controller box (which is unneeded because there is no ground on the STC-1000 and I'm not installing any three prong outlets).

This keeps me from having to run a piece of wire through the side of the freezer next to the soon to be useless ground. I still want the compressor and freezer itself to be properly grounded, and they will be.
 
You're not getting what I'm saying...there is a ground running from a ground bar near the compressor to the thermostat. I'm going to unhook BOTH ends and use the insulated ground as a neutral.[...]

Ok, I got it, you're scavenging the ground wire to use as a neutral. Where are you going to tie that to the line cord neutral? Is there an exposed neutral connection you can tie it to?

Cheers!
 
That's what I'm doing--I'll have a green instead of white neutral.

I haven't found an exposed neutral. If there is one, I'll use it. Otherwise I'll cut the cord, then both tie into the neutral and branch off to continue to the freezer at the cut.
 
I found the neutral where everything terminated...it used blade connectors, so I removed it, cut the female connector off, and stripped the wire. Then I cut the round screw terminal connector on the former ground and stripped it, twisted them together, and crimped on a blade connector intended for automobile use. I figure it will suffice. It fit perfectly over the male blade connector.

Then I checked continuity from the former ground wire turned neutral where it enters the freezer interior to the neutral blade on the freezer plug to make sure I had actually connected to the neutral. There was continuity, so I assume this will work just fine. The only thing that has me slightly concerned is the blade connector. Is there any issue with using it on a 120v A/C circuit?


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You'll find blade (aka spade) terminators used in all kinds of high current applications, so as long as the crimp was solid and the terminator fits tight you should be fine...

Cheers!
 
Good deal! Normally I would have soldered, but there is just not enough room to do that. I'm excited to have it run everything off the factory installed plug, and the fact that I won't have to worry about external wires running into the freezer and all over the place.

I do wish a single stage controller of the STC type were quickly available; it was going to be mid-March before I could get one here from Amazon (shipped on a slow boat the long way from China). I have bottled beer that needs crashing then cellaring next week.


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I finished this today and it works well. Very neat installation with no wires hanging anywhere. I should be able to hold 120 bottles or so.
 
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