Wiring up new compressor fridge

[mariner]

Hi all. I'm hooking up a new CRX50 and need a bit of advice on the wiring as need to replace what was used for the 12v on the old one.

What ampage cable (live and neutral) do I need for the 12v connection to the battery?

I also need to extend the live and neutral from the zig as moving it from the starter battery to a new leisure battery. What ampage is best for these cables?

Do I need to consider the thickness of the new cable, or is it about getting the ampage right?

The previous (original) set up had the neutral (white) cable from the fridge and zig going into a single connector that was then hooked up to the starter battery. Would it be fine to do this again, or should I split these wires.

Thanks for any help. Electrics not my strong point but would like to give this a go.

[slowcoach]

I've never had a zig unit and don't know anything about those..

But for the fridge, I dont think they pull more than 5 amps while running the pump, so any wire that will take over 10amp would be fine. Thickness of the cable can vary, irrespective of amperage.

https://www.ebay.co.uk/itm/264387566364" onclick="window.open(this.href);return false;

16amp thin wall cable here for example..

[Mocki]

I would avoid running the fridge via the control panel , you will suffer with voltage drop, far better to connect directly to the battery via a dutiable inline fuse, keeping wire runs as short as possible.

As a guide the thicker the wire you can use the less voltage drop you will get, running bare minimum rated wire does no one any favours ....

[mariner]

Thanks for the replies. The link to Ebay is great - it's good to be shown exactly what to go for, takes the guesswork out of it!

The plan is to wire directly to the leisure battery under the passenger seat and the fridge is in the usual place behind the driver's seat.

I've found the following for the Zig CF8

This Zig CF8 unit offers leisure battery charging and 230v - 12v conversion with a battery, up to 4.5 amps continuously. Features include: Three 10amp switched and fused outlets for the vehicles accessories.

Going on what Slowcoach said about the fridge drawing around 5 amps, I'm guessing the same ampage cable will work for the Zig unit as the fridge??

The exisiting Zig cable (4mm) is definitely thicker than the existing 12v fridge cable (3mm). Is this to do with the length it runs (back to front of the van)?

[Mocki]

If the control panel has three 10amp outlets , then 5amp wiring isn’t enough!
From your description the 4.5a mentioned is talking about the mains charger side .( doubtful if it really is a 4.5a charger)

That thin wire you describe that went to the original fridge 12v heater is the sole reason that the urban myth that 12v only maintains a already fridge , rather than actually cooling .
Nearly all three way fridges have the same power 12v heating elements as the mains heating element , and if they had Correct wiring to the 12v from the main battery , with no voltage drop , they would cool just as well as the mains .

[mariner]

So just about sorted. Have used 6mm 50A cable from 12volt Planet for both the Zig and the fridge. Fridge is cooling nicely after a a quick test.

Need to just add a couple of inline fuses but not sure what's best. Think the original glass tube fuse was 30/35 for the Zig so reckon a 30amp blade fuse should work, along with a 15amp one for the fridge. Sound about right?

[Mocki]

You should fit the fuse size recommendations of the manufacturer of the fridge , which should be in your instructions.

If it’s a nominal 5amp at max then 10amp would protect your wiring .
The key is that the fuse must be nearest the power supply point and Be lower rating that the wiring and connectors to blow before the wiring gets hot enough to cause damage Should anything go wrong .

[mike9009]

Hi,

I am doing the same thing, installing a new 12V fridge at the moment. It will be hooked directly up to a new leisure battery with a short cable run. I am also connecting the 12v lighting circuit and water pump to the same system. I have a 240v charger to keep the battery topped up when on hook-up or before leaving home. So I won't have a split charger system from the main battery. Hope that makes sense.

Should the new leisure battery have an earth strap to the chassis too? I can only find conflicting advice.

Thanks

[Mocki]

Yes you need to connect the leisure battery to chassis neg .
Always best practice to use the vehicle chassis as neg , much less voltage loss , the chassis can take huge amperage and avoids long neg wires .
Not sure why you wouldn’t have a split charger , for the sake of three more wires and a £10 auto relay .

Make sure all your fuses are as close to the power source as possible , they are there to protect the wiring , not the appliance

[mike9009]

Yes you need to connect the leisure battery to chassis neg .
Always best practice to use the vehicle chassis as neg , much less voltage loss , the chassis can take huge amperage and avoids long neg wires .
Not sure why you wouldn’t have a split charger , for the sake of three more wires and a £10 auto relay .

Make sure all your fuses are as close to the power source as possible , they are there to protect the wiring , not the appliance

Thanks, think I have understood???

I have an autohomes conversion. I am installing the new fridge in the normal place ( opposite sliding door) with the new leisure battery in the next cupboard with a very short cable run. The old fridge had its earthing point next to the fuse box under the dash, so the new fridge's negative cable run is significantly shorter (perhaps 0.5M). Similarly, the lighting circuit has the negative cable run to the front grounding point. Now it will be vastly shorter and obviously drawing less current than the fridge.

Is there a safety concern with simply attaching the negative cable from the fridge/ lighting circuit directly to the battery rather than using a chassis ground?

Thanks for the tip about fuses. I have a small fusebox next to the new leisure battery.

Thanks again - my googling search about all this has been a little fruitless.

[Mocki]

It’s not really a safety issue . It is no safer not to , but it’s the done thing
It also makes connecting the existing van interior lights to the leisure battery much easier and the pin switches still work

I still don’t under stand not having a split charge .

[mike9009]

It’s not really a safety issue . It is no safer not to , but it’s the done thing
It also makes connecting the existing van interior lights to the leisure battery much easier and the pin switches still work

I still don’t under stand not having a split charge .

Understood, basically the long negative wires give a voltage drop and less efficiency due to more power being required?

I think our usage would not require a split charger as we tend to go to one site and stay for almost a week and then move on. I can add at a later stage if need be. I like to do stuff step by step, especially when it is a little out my comfort zone (or new to me) I was also thinking about adding solar later if need be.

Those are my excuses!

Thanks for your knowledge - really appreciated.