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Breaker size conflict between installer and inverter manufacturer

AntonieCebu

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Joined
May 21, 2022
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Hey guys,

This is a follow up for a different issue I had (original post here: https://diysolarforum.com/threads/nominal-operating-voltage-360vdc-powmr-5kw-hybrid-question.40393/ )

Now the manufacturer of the hybrid inverter PowMr (5000W/80A/48v) is saying we need to use a 100A+ breaker for our battery blue carbon lifepo4 48v 10000W/200AH and a 25A breaker for our solar array (10x450W/48v in Series)

Our installer is saying 63A for the battery and 63A for the solar array is needed.

They are using 25mm wire and it's a single phase inverter.

Can anyone tell me which party is correct?

All help appreciated. I've also attached the manual of the inverter
 

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Our installer is saying 63A for the battery and 63A for the solar array is needed.
Well 5000W at 48V nominal is over 100A for inverter draw, and if 80A SCC in that powrMR that is probably more than 63A in most countries so at best your installer is flat out wrong to begin with.

Get a different installer or DIY it imho
 
Fuses protect wires. Fuse to protect the 25mm cable. Manufacturer listed minimal sizes should always be respected. Use larger than 100 ampere fuse.
 
Let's just crunch some numbers on this one:

5000w / 48v = 104.1a
104.1a * .85% efficiency = 120a
120a * 20% overhead = 143.75a which would be 150a retail

Your installer is wrong on that one.

When measuring using a multimeter we are at 350VDC. I'm assuming my installer is correct but I wanted to check with you guys as well.

SCC goes like:
4500w / 350v DC = 12.85a
12.85a * 20% overhead = 15.42a

The array calling for 25a seems a bit high actually, but the wire size would really be the determining factor. That would be about the limit of 12AWG wire capacity. 63a on your panel wiring incoming is really high and wouldn't protect the wires.
 
the wire size would really be the determining factor.
Fuses protect wires
Yup - I totally didn’t even think to mention that. I was assuming adequate wiring maybe but I always fuse for the equipment because I overcable 1-3 gages on inverter and SCC wiring.
A moment of narcissistic myopia.

(when I overcable I fuse for equipment rating because- in theory- that may prevent the equipment from being the practical fuse which in my mind is called a fire.)
 
Thanks Guys so much. The wiring used is 25MM/4AWG. They will come tomorrow to change the breakers, hopefully that will solve the problem I'm seeing from my original post.
 
4AWG from the panels to the SCC? Am I missing a combiner box or something here? If they're 4AWG then the 63a breaker makes a lot more sense as it should be sized to the wire and not the load. As in the load determines wire size and the wire size determines the fuse size.

What's the wire size and distance between the battery and the inverter? According to the famous BlueSea Amperage chart 4AWG is the absolute smallest you should use and that's if you de-rate. 1/0 would be the correct size for your load (150a) from inverter to battery.
 
4AWG from the panels to the SCC? Am I missing a combiner box or something here? If they're 4AWG then the 63a breaker makes a lot more sense as it should be sized to the wire and not the load. As in the load determines wire size and the wire size determines the fuse size.

What's the wire size and distance between the battery and the inverter? According to the famous BlueSea Amperage chart 4AWG is the absolute smallest you should use and that's if you de-rate. 1/0 would be the correct size for your load (150a) from inverter to battery.
I took some pictures, sorry I'm pretty much a big beginner
 

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