Help bypass fridge thermostat with stc

So I've read that some people just cut the wires to and from the thermostat and plug them into the cool relay on the stc.

Seems simple enough. But I'm confused when it comes to my fridge. There's no actual temperature knob or anything, there's just some LEDs displaying the current temp in the fridge.

On the first picture the wire going out to the left leads to the LEDs on the second picture. The other cable is for the mains. How should I do this?

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First of all, where do you adjust the fridge temp? Are those leds buttons? If so, then that is a digital thermostat. Other than that there must be an adjustment dial somewhere.

Blitzkrieg said:

First of all, where do you adjust the fridge temp? Are those leds buttons? If so, then that is a digital thermostat. Other than that there must be an adjustment dial somewhere.

Click to expand...

I don't know. Someone gave it away yesterday and I picked it up. I think it's a pretty old fridge. Those are not buttons, just lights.

Okay. I plugged it it and gave it a try. It's an electronic thermostat. The blue field is actually a button where I can set the temp. Can I just cut this part out of the loop and add my stc?

I guess (although I have no skills with fridges whatsoever. ) the compressor is only getting an on/off signal from the thermostat. Or a dimmed signal or something. If I bypass it and add my stc will it be the case that the compressor will be working at 100% when it's on? Wouldn't it in that case work just bypassing the thermostat?

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The compressor always works at 100%, the thermostat just opens and closes a circuit, you should be able to cut the wire going to the thermostat (keep in mind that if the fridge has a light that it probably gets power from this same circuit) and wire it into your stc. Obviously you want to do this with the fridge unplugged.

Ok. Thanks. But just to get it in with a teaspoon:

I cut the mains wire. Split both leads, rewire the mains off one end of the split back to how it was. Take both leads off the other end of the split and feed them into the stc. Cut the wire to the thermostat and plug both into the cold relays on the stc?

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Uh that sounds way over complicated. The wire with the plug on it shouldn't be touched, it runs into a panel on the compressor and is split so that the hot wire has to go through the thermostat before it gets to your compressor. The other wire (the one going to the thermostat) is where you want to wire in your stc. But like I said if you just cut it without having access behind the thermostat you won't be able to wire in your light. In behind the existing thermostat the wire we are talking about cutting splits again to give neutral and hot to the lighting circuit. Also, depending on how fancy the fridge is there may be a heating circuit for the door seal that is run off the thermostat (to avoid condensation).

One solution would be to open the cover behind the compressor and disconnect the compressor's hot wire. Replace this with a new hot wire coming from your stc. Without cutting anything you should be able to branch the neutral and hot under that cover to power your stc. Just make sure to properly cap the disconnected hot wire since it will be live from time to time.

Is there a wiring diagram / schematic of the fridge you could post?

Then how do I power the stc?



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Sorry got hung up on the first part of your post.

But will my idea work? The way I see it it's actually easier. I cut the cables I mentioned, running hot and neutral to power the stc. Cut the cable running to the thermostat and wiring a new cable in its place back and forth through the cool terminals of the stc.

If I run a cable with four leads it's just one cablestretch and I don't have to dig around behind the fridge as much.

I don't care about the lights either. I'll use the stc as an indicator. Maybe placing a pilot light on the hot main before the stc so I can differ between dead mains and dead stc.

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raouliii said:

Is there a wiring diagram / schematic of the fridge you could post?

Click to expand...

Unfortunately not. The only info I could find on it was a manual without a schematic on neighboring model.

I'm kind of electronically retarded. Mostly know the don't s when it comes to electricity.

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I am gonna need some sort of diagram to understand exactly what you are saying. The reason I suggest opening the electrical box mounted to the compressor is that it will give you a good safe grounded place to branch your mains wire.

Heres a simple paint sketch of what you would want to do inside that electrical box:

Ok. So I got back home and popped the fridge open. Now I got a better understanding about what Blitzkrieg tried to tell me.

This is what it looks like under the hood at the top.

The brown, blue and black on the left are coming from down under. Both blue and brown are splitted at the compressor end from the mains. The black is going back to a plug marked "c", which I guess stands for compressor, at the compressor end.

So. I cut this three - lead wire in two and make a split with the brown and blue, and totally cutting the black.

Rewire brown and blue back so they still lead to this part with electronics on the top.

Take the other split ends of brown and blue into the stc mains while also taking the brown to the input of the cool relay on the stc.

Plug the black wire into the output of the cool relay on the stc.

All lamps and sensors and stuff should still work on the fridge.

Is this correct? I shouldn't have asked all these questions before I looked at what I'm actually dealing with here..

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Blitzkrieg said:

I am gonna need some sort of diagram to understand exactly what you are saying. The reason I suggest opening the electrical box mounted to the compressor is that it will give you a good safe grounded place to branch your mains wire.

Heres a simple paint sketch of what you would want to do inside that electrical box:

Click to expand...

I don't get the relay wiring on the stc on your diagram. I need two cables, "in" and "out". On your diagram I only see one.

Here's what I'm thinking:



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On the very top I'm guessing that the "c" is the return after thermostat (the hot).

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You are right, you need two hots going into the STC, I made that diagram in like the last 3 mins of my break... also where I wrote hot out it should be the cool circuit and not the heat circuit.

Your diagram looks correct, you have both Hot and Neutral going to the old circuit so you will still have lighting and you have both Hot and Neutral powering the STC, and hot being switched at the STC going to the compressor.

And after reading your description a couple of times for clarity it seems that you are on the right track. Just make sure you cap whats left of that black wire if you dont remove it from the circuit board completely, it can be dangerous because you wont have any warning as to whether or not it is powered. Could be live one minute then dead the next.

I must admit to being a bit confused here.

Why not build a simple controller outlet box using an STC-1000 and then plug the fridge into it? That way, you accomplish the same level of control without any modification at all to the fridge.

Blitzkrieg said:

And after reading your description a couple of times for clarity it seems that you are on the right track. Just make sure you cap whats left of that black wire if you dont remove it from the circuit board completely, it can be dangerous because you wont have any warning as to whether or not it is powered. Could be live one minute then dead the next.

Click to expand...

Nothing will be unplugged. The black wire will be the return from the STC "cold" (the hot wire in to the compressor).

BigFloyd said:

I must admit to being a bit confused here.

Why not build a simple controller outlet box using an STC-1000 and then plug the fridge into it? That way, you accomplish the same level of control without any modification at all to the fridge.

Click to expand...

I have two of those external boxes already, and to be honest they annoy me a bit with cables dangling here and there, and a loose box.

I also want to build it, because it's fun, and it's slicker with just the fridge with the controller built in to it, instead of having a box on top.

Well, it wouldn't be the same level of control. Lets say the thermostat in the fridge is off, and will not cool under 4 degrees C. Then even if I set the STC to 2C, it wouldn't get under 4 degrees since the fridges thermostat has the last word. By bypassing the fridges thermostat the STC is the reigning king of lagering.

Smellyglove said:

Nothing will be unplugged. The black wire will be the return from the STC "cold" (the hot wire in to the compressor).

Click to expand...

Sorry. Yes I'll cap this one.

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Smellyglove said:

Well, it wouldn't be the same level of control. Lets say the thermostat in the fridge is off, and will not cool under 4 degrees C. Then even if I set the STC to 2C, it wouldn't get under 4 degrees since the fridges thermostat has the last word. By bypassing the fridges thermostat the STC is the reigning king of lagering.

Click to expand...

That's a good reason. I guess that I'm fortunate that my fermenter fridge will go down to a hair under 2*C and that I have an upright freezer for lagering/crashing. If you like to do lagers, a second unit is a real blessing.

Turned out pretty nice. And it even works!

Thanks for all your help on this.

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Nice build. That looks pretty darn pro.

Like a boss, Nicely done. Much cleaner than one of those hot tub panel box dealys.

Im now on my third fridge. This one had a relay with a ground wire going to it. I removed the thermostat and replaced it with a stc. What do I do with the ground wire?