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frosty avatar image
frosty asked

Phoenix inverter (12v 3000w 230v) cable size.

Hi, could someone be kind enough to confirm the battery to inverter cable size on a 12v 3000w Phoenix inverter? The manual states it it should be 90mm2, this seems awfully large considering the carrying capacity of this cable is 500a, the inverter will never be used continuously at full power and the cable run is around two meters, I currently hold plenty of 70mm2 cable and thought this would be sufficient given a carrying capacity of 485a. I look forward to hearing some feedback.

Thanks in advance.

James.




wiring
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4 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

I would also recommend 95mm². But it depends on how much power you want to draw and how long. To thin wires result in a higher voltage drop and can cause a low voltage cut-off.

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frosty answered ·

The power draw would be short and intermittent and for not very long as it would mainly be for cooking on a dual zone induction cooker, the rated power is 2.9kw but it would never be used on full power, with such a short cable run I thought 70mm2 would be well within demand but I guess its probably best to follow victrons recommendations regardless?

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JohnC avatar image
JohnC answered ·

Hi @Frosty

Note well that this post of mine is not a Victron recommendation. Which are always at the conservative end.

I ran another-branded 12/3kV inverter for years succesfully with 70mm2 cable and a 400A fuse. That was what they said, so I did it. And still use the same cable with a 48/5000 Multi (as per Victron).

It should be ok to use 70mm2 over a short length and loads, but fuse it to a max of 400A, even less if you can get away with it.

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frosty avatar image frosty commented ·

Hi John, appreciate the reply, I had planned on fusing the inverter at 350a with a 400a class T at the positive terminal so I would have thought with this setup I should be fine running on 70mm2.

With regards to the recommended 90mm2 cable perhaps this is based on continuous working current where heat build up within the cables could become a problem?


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zoneblue avatar image
zoneblue answered ·

In these situations it helps to understand the voltage drop on the cable. At 320A, about 0.2V for 70mm2 cable 2m each way seems bearable. Just be aware at that current every little bit adds up, a not so tight lug nut, a breaker / switch /fuse with a bit of resistance. Generally people go to a higher system voltage for an inverter that size for these reasons.

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