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Old 19-09-2016, 01:53   #1
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Use AC fridge digital temp switch with DC

A friend gave me a digital fridge temperature switch unit to use on my boat.

However, I noticed that it seems to be an AC unit (see attached images). It is called an STC-1000 - no idea where they got it from.

I'm not good enough with electrical theory to know if an AC unit would handle DC??

So my question is, can you use this in a 12v DC system?

Thanks

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Old 19-09-2016, 01:57   #2
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Re: Use AC fridge digital temp switch with DC

Search posts by Typhoon and recent refrig threads, you will find bunch of info.
Cheers
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Old 19-09-2016, 02:11   #3
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Re: Use AC fridge digital temp switch with DC

Since it says on the input that its 12V AC there is probably a diode bridge inside it to turn it into 12V DC. I'd be inclined to hook it up to 12V DC and see if it works. 12V AC is so unusual anyway that I'd say its probably typo by an oriental anyway.
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Old 19-09-2016, 02:22   #4
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Re: Use AC fridge digital temp switch with DC

...or you could start here:

Running freezer as a fridge
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Old 19-09-2016, 08:18   #5
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Re: Use AC fridge digital temp switch with DC

Cheers!
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Old 19-09-2016, 15:04   #6
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Re: Use AC fridge digital temp switch with DC

There is a big issue with using any AC switch on a DC circuit - beware.
AC switches have a small gap, slow break because the alternating current breaks the spark. Use it on DC and the voltage is constant in one direction so the arc does not break quickly. Contacts will pit and could well together in a short, or long, time.
By all means use it if it works, but do not expect 10 years service with no risk.
Roger
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Old 19-09-2016, 16:49   #7
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Re: Use AC fridge digital temp switch with DC

Google STC-1000 and you find them on ebay for less than $10, and a few you tube videos. Seems popular with people who home brew beer so at least it has that in common with boats.
As far as using it on DC a definite maybe. The relay for the heating and cooling contacts might be DC coils if the internal rectifier is driving them. I see the relay contacts are rated for 10A AC, derate it by a few amps for DC. Test it first on DC with an inline fuse of 2A, if the unit lights up and the fuse doesn't blow then your off to a good start, otherwise your out $10.
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