I have 2x Phoenix 48V 5000VA inverters (about to be configured for parallel operation) supplied from 4x 25.6V 200Ah LiFePO4 Victron Smart Lithium batteries (2P2S configuration) with a Victron BMS v2. I am wiring the AC output of the inverters to an AC combiner box before feeding it into the house consumer unit. It is all off-grid. My question is about wire type primarily, although advice on wire size is also welcome. I am installing the batteries and inverters in a separate outbuilding for safety. I have used 10mm2 NYY-J 3 core (L,N,E) outdoor rated cable from each inverter to the combiner box, and 16mm2 NYY-j 3 core from the combiner to the house CU, rather than SWA as the cable does not need to be buried. Each of these cables has 7 thick strands in the conductors. The combiner box includes a 40A MCB for each inverter input, and a 2 pole 125A isolator switch for the output. It’s from Voltacon but I’ve fitted 40A B curve MCBs in place of the original 63A C curve ones which would have been too high a tripping current for my application. Now, the wiring output terminals of the inverters are screw terminals which appear best suited to fine multi stranded wire but I cannot find any type of AC cabling with sufficient cross-sectional area which is finely stranded. And in domestic AC installations only single strand (up to 4mm2) or thick multi strand (7x) wires are used. So what is the best option for Inverter output wiring? Thanks in advance for advice and suggestions.
Is a decent size for 5kva as it is usually around 30A (30A x 230v is 6900w) rated.
4mm from each inverter is theb 60A for the feed to the combiner.
In parallel set ups you usually want to use a gauge down anyway as it helps with balancing the current between inverters.
Thanks. The peak output of the inverters is 10kW so I don’t want to risk overheating / voltage drop in 4mm2 CSA. Does 10mm2 count as too big?
Flat blade ferrules may be something to look at if you are concerned aboit the hard drawn cable in the terminals of the phoenix?
From each inverter to the combiner point
Or
From combination to DB? For this part it is less critical except for ampacity. So what is the amp rating of the 10mm?
Good suggestion. I didn’t see any mention of ferrules in Victron’s Phoenix Inverter documentation. Are they a good enough alternative to fine stranded conductors?
10mm2 for the cable from each inverter to the combiner. I calculate 44A per inverter at 230VAC.
Sorry, i got something mised up here in my head.
How long are the runs?
Did you read the manual?
I did but I’ll have another look. I noted the point and (extreme) examples about cable resistance mismatch causing imbalanced inverter load. The run from each inverter to the combiner box is 1m. The run from the combiner to the house CU is 3m.
Well the proof is always in the eating.
You have short runs. Do you have a good clap meter for checking balance?
Yes I have a Fluke AC/DC clamp meter which is pretty accurate. Thanks for the suggestion. I’ve ordered some crimp-on flat blade ferrules. I have a manual hydraulic crimper which does a good job.
I guess if they’re not balanced I just have to reduce the CSA of the conductors or maybe increase the length to the combiner box.
Basically, yes.