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Freezer Wiring - How To Bypass The Thermostat?


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8 replies to this topic

#1 bugwan

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Posted 13 January 2007 - 06:03 PM

Hi guys, well I haven't had the greatest run with eBay fridges, but I just scored a 340 litre chest freezer for $11.50, so I figure if this one dies, it's hardly an issue...

I bought it knowing there might be some issues with it, but it sounds like the thermostat is playing up, so I'd like to bypass the thermostat to see if the freezer comes down in temp (at least then I know it's not the compressor/overload etc).

Since I don't have a schematic, I took some pics below and I'd love it if someone could please help me get the wiring right to bypass the thermostat. I've signed a waiver to forfeit any personal injury claims, so don't be shy!

The first one is the overall wiring, with the thermostat unit unscrewed to show the paths of the wires. My thinking is that to bypass the thermo, I can take the brown wire (live) and attach it to the yellow wire (which goes straight to the overload on the compressor. Is this right?
Attached File  Overall_wiring_with_thermo_moved.JPG   41.82KB   34 downloads

The other (white) wire heads off from the thermo to an indicator light at the front of the freezer unit and comes back to connect to neutral at the Klixon thingo.
Attached File  Thermo_moved_closeup.JPG   34.82KB   27 downloads

Here's the overall wiring setup:
Attached File  Overall_wiring.JPG   42.6KB   21 downloads

...and a closeup of the thermostat wiring:
Attached File  Thermo_wiring.JPG   56.64KB   16 downloads

This is probably eye-rollingly simple for someone with a brain, but this is something I seem to be lacking.

I have a fridge temp controller, so I intend to use that to keep the freezer at around 4 degrees. Is is safe to run the freezer long-term with the thermostat bypassed? Or should I get a new thermostat, even though I'm using a temp controller?

So many questions, thanks in advance for any assistance.
Dave.

Edited by bugwan, 13 January 2007 - 06:03 PM.


#2 WortGames

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Posted 13 January 2007 - 08:43 PM

I can't quite see where a couple of the wires end up, but the bottom line is that you just need to get mains power to the compressor.

The neutral (blue) wires are probably already directly connected, so you just need to get the live wire to the other terminal (ie the yellow wire). The live wire is the one that is being switched by the thermostat - you need to take off that brown cover, find where the live wire (probably brown) comes in, and somehow connect it across to the yellow wire that goes to the compressor.

Obviously this information is provided for entertainment purposes only...

#3 bugwan

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Posted 13 January 2007 - 08:54 PM

I can't quite see where a couple of the wires end up, but the bottom line is that you just need to get mains power to the compressor.

The neutral (blue) wires are probably already directly connected, so you just need to get the live wire to the other terminal (ie the yellow wire).


Thanks for your reply Wortgames. Regarding the above, I presumed as much. Direct power to the compressor was what I was trying to achieve (to simulate warm freezer temps), but I just didn't have my common sense hat on. The yellow wire heads to the overload, which then heads to the relay. I presume that completing that circuit would kick off the compressor. (As long as it doesn't kick me out of the shed, I'm happy).

Obviously this information is provided for entertainment purposes only...


;)

Thanks Wortgames, will run your scenario through my head and see what I can come up with.
Dave.

#4 bugwan

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Posted 13 January 2007 - 09:04 PM

More photos of wiring...hopefully they are of some help.

Attached File  Power_wiring.JPG   30.72KB   36 downloads

Attached File  Klixon_closeup.JPG   36.35KB   29 downloads

#5 WortGames

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Posted 13 January 2007 - 09:17 PM

OK, that all seems to make sense - the box is just a (ridiculously large, empty) junction box - no surprises inside.

You can just short-circuit between the brown and yellow wires right on the back of the thermostat. Use a paper clip or something, then switch on the power from a safe distance.

Does the white wire join onto the chassis with the green ones? If so it's just an earth for the thermostat.

#6 Screwtop

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Posted 13 January 2007 - 09:18 PM

Just jumper/bridge the thermostat out, don't move wires. If you have a multimeter find the mains Active (Red/Brown). Then with the probe on the other side of the thermostat look to see which terminal is switched (becomes active) when the thermostat switches. Remove from power and add a wire jumper from the Active in to the switched active out side of the thermostat, easier to reinstate later.

This information is intended only for use by suitably qualified tradespersons.

#7 bugwan

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Posted 13 January 2007 - 10:54 PM

Thanks for your replies guys...sorry, I've been in the middle of a West Wing marathon with SWMBO :excl:

Red to yellow seems the natural order of things Wortgames & Screwtop.

The white wire actually heads off to the "safety light" indicator on the front of the machine, and isn't related to the earth. The white wire then returns (coloured blue) to the relay. I guess it's just an indicator that the circuit has been completed (ie. compressor is running/receiving power) without having to remove the external cover or use a multimeter.

Cheers again for your assistance guys.

#8 bugwan

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Posted 14 January 2007 - 12:07 AM

OK then, not good news...

I tried bypassing the thermostat and the same thing happened...the compressor tried to run for about 15 seconds and then stopped. The overload is cutting it out.

Does this mean a locked rotor? And if so, can I jump start it back into existence somehow? Maybe a 'hard start kit'??

edit: I tried a different overload and that got me the same result. It looks like the issue is with the compressor.

Edited by bugwan, 14 January 2007 - 12:09 AM.


#9 WortGames

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Posted 14 January 2007 - 09:31 AM

You could try giving the compressor a couple of whacks with a rubber mallet as you start it up. It might just be enough to free the rotor - although I'd have to say the chances are slim - it's probably seized and/or burnt out in there.

Don't lose heart, I got my chest freezer on eBay ($70) and it's been brilliant.