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Using aluminum #1

I

Ironman

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Nov 29, 2020
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I have a couple hundred feet of Aluminum underground wire meant for feeding a house with 120/240v I think it is 9 strands of aluminum.
I am wondering if I can use it to carry power from the solar panels to the inverter. I understand DC current flows best in a multiple fine strand wire, like welding cable. This will have a 100volt nominal voltage at 60 amp maximum feeding from the combiner box to the inverter, so it may not have a great amount of loss.
Anyone done this?
 
If I remember correctly back in the day they tried using aluminum for house wiring and the issue they ran into was the connections.
If you have a screw lug like in an electric box that's one thing but I don't know how you handle a crimp end like you would if your using MC4 connectors.
 
Ironman said:
Sorry. I knew I would forget something.
Click to expand...

And wire gauge? That will determine if it’s safe.

I doubt it would be a problem.

60 amps at 100v is a big solar array. Wish I had 6 kW available.

I wouldn’t buy it for that purpose but if you have it on hand for free that’s hard to beat.
 
If you're going to do anything with aluminum wire, make very sure you use the proper Al bonding paste for it. The bonding paste prevents the Al from oxidizing to aluminum oxide, which is an insulator. I would make sure all connections were trimmed back to shiny new metal before even trying to add the bonding paste.
 
60A requires roughly 4 AWG if I'm not mistaken (not an electrician and this is not advice). It costs $1.32/ft at WireAndCableYourWay.com, a retailer I have used in the past and liked their service. Since it's DC let's assume you need two conductors plus one ground of equal gauge so at 60' length that's $238, without even shopping around at all.

This may depend on your financial situation but aren't you about to do roughly $2000 worth of labor digging a 60' long trench? I wouldn't skimp on the wire I bury underground, but I know $238 isn't nothing. In fact, what I listed was THWN-2, so it should go in a conduit anyway, and that's going to be another $100 or so added to the cost. If what you have on hand is direct-burial cable I'd say go for it, but to me another $250 or so on top of a 6kW solar array is sort of insignificant and you should just use copper.
 
I would still use the proper MC4 wire to avoid all the aluminum to copper and large to small wire transitions.
Get the right stuff.
 
paul12345 said:
60A requires roughly 4 AWG if I'm not mistaken (not an electrician and this is not advice). It costs $1.32/ft at WireAndCableYourWay.com, a retailer I have used in the past and liked their service. Since it's DC let's assume you need two conductors plus one ground of equal gauge so at 60' length that's $238, without even shopping around at all.

This may depend on your financial situation but aren't you about to do roughly $2000 worth of labor digging a 60' long trench? I wouldn't skimp on the wire I bury underground, but I know $238 isn't nothing. In fact, what I listed was THWN-2, so it should go in a conduit anyway, and that's going to be another $100 or so added to the cost. If what you have on hand is direct-burial cable I'd say go for it, but to me another $250 or so on top of a 6kW solar array is sort of insignificant and you should just use copper.
Click to expand...
OK, I paid $40 for a 250 meter roll of this stuff. It was not needed by the original owner. I tend to grab stuff like that when it floats by.
I have a mini excavator to do my trenching.
Your point about cost is valid, and maybe cheaping out on the DC side is not good. This will work fine for the AC side.
 
wiring with aluminum has many secondary issues including: more delicate than copper, corrosion, cold creep, unable to solder, and is about 50% as conductive...
it certainly is a conductive metal wire and can be used; you just need to take into account all the other little gotcha's. This is why you can look up the rules in the NEC about where, when, and how you can use aluminum wire.

so a 60ft distance from panel to box is 120ft of aluminum wire; thats quite a distance.


here is a voltage drop calculator that lets you pick Al wire...

American Wire Gauge Chart and AWG Electrical Current Load Limits table with ampacities, wire sizes, skin depth frequencies and wire breaking strength

AWG Wire size chart and ampacity table for design engineers including skin depth frequencies and tensile strength data; electrical cable size
www.powerstream.com
 
The #1 aluminum will be fine if you can handle the terminations.
 
Thanks for all the input. I think I will keep my ears up for some good copper wire
 
If cost is no object, copper is always preferred, but for a run of 60 feet, underground in a conduit, I would not discount the #1 aluminum you already have. As mentioned earlier, pay special attention to the terminations and you will be fine - Study up on how to properly terminate aluminum wire. Big power loads using aluminum wire are fine - The power company does it every day

Don
 
General rule of thumb, Al needs roughly 1 step up size-wise over Cu for the same amperage, but consult an amperage chart (I think that 1ga should be OK for 60A but check a chart and be sure you can live with the voltage drop it will produce).

I assume you will have a combiner box with breakers and buss bars at the PV end, and a breaker box of some sort at the other end of the run. As long as all those boxes/buss bars/connections are rated for Al wire you should be OK. Of course do a proper Al install with the right de-ox paste, and proper torque for Al wire.
 
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