Rewiring fridge to bypass thermostat (for external control)

[Ismabard]

Hi,

I'm attempting to adapt a fridge into a homebrew fermentation chamber with a digital thermometer controlling the compressor via an arduino and relays. Initially, all I need to do is take out the thermostat and rewire so that the compressor always runs when the power is on, ideally with the light also running in parallel so it can be separately controlled later.

I'm having trouble identifying which wire is which however, and seem to have more than I was expecting: 5 total. Other than the green/yellow earth I couldn't say which is which. Could anyone advise me based on the colours and typical functions (green/yellow, brown, black, blue, white.) Presumably one of these is a separate connection for the light, but unless two are neutral that still gives me one more than expected. I've included pictures with and without the thermostat attached, but the plastic casing of the thermostat makes it quite hard to trace the connections. Alternatively if anyone knows where I could get a circuit diagram for a Zanussi fridge that would be excellent.

Any help and advice appreciated. Thanks

 

[pto]

Hi,

I'm attempting to adapt a fridge into a homebrew fermentation chamber with a digital thermometer controlling the compressor via an arduino and relays. Initially, all I need to do is take out the thermostat and rewire so that the compressor always runs when the power is on, ideally with the light also running in parallel so it can be separately controlled later.

I'm having trouble identifying which wire is which however, and seem to have more than I was expecting: 5 total. Other than the green/yellow earth I couldn't say which is which. Could anyone advise me based on the colours and typical functions (green/yellow, brown, black, blue, white.) Presumably one of these is a separate connection for the light, but unless two are neutral that still gives me one more than expected. I've included pictures with and without the thermostat attached, but the plastic casing of the thermostat makes it quite hard to trace the connections. View attachment 47557 View attachment 47559 View attachment 47558 Alternatively if anyone knows where I could get a circuit diagram for a Zanussi fridge that would be excellent.

Any help and advice appreciated. Thanks

black compresor brown live blue neutral white defrost heater

 

[Ismabard]

Ah ok. Thank you. I hadn't even thought about the defrost heater. I won't need that because the running temperature of the fermentation will be hotter than the fridge's normal range anyway.

I may be showing my ignorance of circuitry here then, but how can there be live and neutral wires AND separate ones for the components? In order to power something, surely the live and neutral lines have to run through it. If they also have their own cables how can the circuit complete?

If as I say, I want to just wire the compressor to run all the time (with everything still safely earthed ) can you tell me which ones I should connect?

 

[pto]

Ah ok. Thank you. I hadn't even thought about the defrost heater. I won't need that because the running temperature of the fermentation will be hotter than the fridge's normal range anyway.

I may be showing my ignorance of circuitry here then, but how can there be live and neutral wires AND separate ones for the components? In order to power something, surely the live and neutral lines have to run through it. If they also have their own cables how can the circuit complete?

If as I say, I want to just wire the compressor to run all the time (with everything still safely earthed ) can you tell me which ones I should connect?

Ah ok. Thank you. I hadn't even thought about the defrost heater. I won't need that because the running temperature of the fermentation will be hotter than the fridge's normal range anyway.

I may be showing my ignorance of circuitry here then, but how can there be live and neutral wires AND separate ones for the components? In order to power something, surely the live and neutral lines have to run through it. If they also have their own cables how can the circuit complete?

If as I say, I want to just wire the compressor to run all the time (with everything still safely earthed ) can you tell me which ones I should connect?

black and brown

 

[telectrix]

see which 2 wires open/close as you turn the stat.

 

[jamie-spark]

Hi,

I'm attempting to adapt a fridge into a homebrew fermentation chamber with a digital thermometer controlling the compressor via an arduino and relays. Initially, all I need to do is take out the thermostat and rewire so that the compressor always runs when the power is on, ideally with the light also running in parallel so it can be separately controlled later.

I'm having trouble identifying which wire is which however, and seem to have more than I was expecting: 5 total. Other than the green/yellow earth I couldn't say which is which. Could anyone advise me based on the colours and typical functions (green/yellow, brown, black, blue, white.) Presumably one of these is a separate connection for the light, but unless two are neutral that still gives me one more than expected. I've included pictures with and without the thermostat attached, but the plastic casing of the thermostat makes it quite hard to trace the connections. View attachment 47557 View attachment 47559 View attachment 47558 Alternatively if anyone knows where I could get a circuit diagram for a Zanussi fridge that would be excellent.

Any help and advice appreciated. Thanks

I would be a lot simpler and safer if you use one of these below. Great bit of kit, it has heating and cooling functions , plug fridge in the cooling and heatmat in the heating side. bobs your uncle presicion temperature control

https://www.amazon.co.uk/dp/B018K82...t=&hvlocphy=1007406&hvtargid=pla-421578911488

 

[Ismabard]

Thanks all. I'm afraid I'm still a little bit in the dark.

see which 2 wires open/close as you turn the stat.

I can't easily see inside the thermostat, but isn't it just a variable resistor? I don't think there is any setting which would connect or disconnect the wires - surely then the compressor would either always or never function deplending on the setting.

I would be a lot simpler and safer if you use one of these below. Great bit of kit, it has heating and cooling functions , plug fridge in the cooling and heatmat in the heating side. bobs your uncle presicion temperature control

https://www.amazon.co.uk/dp/B018K82...t=&hvlocphy=1007406&hvtargid=pla-421578911488

I'm looking at using something very similar to this, but in normal operation the thermostat will turn off the compressor if the fridge gets too cold. I need to wire it so the compressor always runs. Then I can use the external controller to turn it on and off.

 

[Ismabard]

I have also taken some voltage readings though that hasn't cleared much up: 240v across yellow/green and brown, brown and blue, brown and black. 0v across everything else.

Assuming y/g is indeed earth that would mean brown must be high. That would make blue and black both low. However there's also 0v between white and brown, which would make white high, except that white and y/g is also 0v. Perplexed.

I don't know if I could try taking a current reading for these too which might give more information, but I'm worried if there is no load in the circuit I'll blow up my multi-meter and/or fridge.

Regarding wiring diagrams, its a Zanussi ZRA40400XA. I get lots of hits on google but following them through can't see anything with the actual schematic.

Thanks for continued help. I really didn't think this would be this hard!