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PV wire or THHW or?

Mike.Indiana

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Aug 11, 2021
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I cant seem to find the answer. Im building a ground base system its 100ft form the house with 50ft undergorund conduit.

I think THHW wire is an acceptable substitute for PV wire? Im concerend about the cost and difficulty of working with PV wire.

Will the MC4 connectors work with either type of wire?

Thank you
 
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Any wire suitable for the voltage, current and conditions can be used. PV wire has the benefit of UV resistance since there's a good chance the wires themselves may be exposed to sun.

MC4 connectors work best with the insulation on PV wire in 10 and 12 awg - sometimes 8awg. If you're going to rely on the weather-proof-ness of the MC4 connector, that's likely your biggest concern.
 
I cant seem to find the answer. Im building a ground base system its 100ft form the house with 50ft undergorund conduit.

I think THHW wire is an acceptable substitute for PV wire? Im concerend about the cost and difficulty of working with PV wire.

Will the MC4 connectors work with either type of wire?

Thank you
What would generally be done in a situation such as this is to run the ‘home run’ in conduit from the house to a junction box near the array (using whatever wire is properly rated for temps and currents involved) and then make a junction between home run wires and PV wire before exiting the junction box and connecting to solar panels using MC4.

Often, the junction box will be a PV combiner box allowing parallel combining of two or more PV strings in 10AWG PV wire to be combined to larger AWG wire for the home run.
 
What would generally be done in a situation such as this is to run the ‘home run’ in conduit from the house to a junction box near the array (using whatever wire is properly rated for temps and currents involved) and then make a junction between home run wires and PV wire before exiting the junction box and connecting to solar panels using MC4.

Often, the junction box will be a PV combiner box allowing parallel combining of two or more PV strings in 10AWG PV wire to be combined to larger AWG wire for the home run.
thank you for the response. That makes since. However i speced the panels so i dont need a combiner box. Im running 16 440W bifacials. 4 Sets of 4. Each set is in series. 200V @11A per set. So i will make 4 runs directly from each set to the 4 pv inputs of a pair of lv6548 inverters. The farthest set is 100ft to the inverter so i think 10ga all the way is good. Does that make since? thank you for your help.
 
thank you for the response. That makes since. However i speced the panels so i dont need a combiner box. Im running 16 440W bifacials. 4 Sets of 4. Each set is in series. 200V @11A per set. So i will make 4 runs directly from each set to the 4 pv inputs of a pair of lv6548 inverters. The farthest set is 100ft to the inverter so i think 10ga all the way is good. Does that make since? thank you for your help.
If it were me, I’d want two home runs in order to feed two inverters (but if each of those 3 inverters has 2 MPPT inputs, then you’ve got it right with 4 home runs).

As far as wire guage, 10 AWG is certainly big enough to handle 11A but you will lose a lot of voltage over a ~200ft (round-trip) home run.

I’d suggest to use one of the wire-loss calculators to estimate the difference in running your home run wires in 8AWG versus 10AWG and then price it out both ways…

Also, if you are going to run more than 3 current-carrying conductors in any single conduit, there is an additional derating factor, so be certain you are calculating current-carrying capacity of you home run conductors correctly…
 
Not sure if your PV wire is rated for being submerged. (there are many different versions of PV wire and I don't know if you have rated wire for sitting in water). THHW is. (that is what the W in THHW is for)

When cable is in conduit is can always trap water so the wire have to be rated to be under water.

I am running the same 4x4 panel setup on 10 awg but with 305 panels....your amperage of 44 amps is to high for 10 awg.
 
If it were me, I’d want two home runs in order to feed two inverters (but if each of those 3 inverters has 2 MPPT inputs, then you’ve got it right with 4 home runs).

As far as wire guage, 10 AWG is certainly big enough to handle 11A but you will lose a lot of voltage over a ~200ft (round-trip) home run.

I’d suggest to use one of the wire-loss calculators to estimate the difference in running your home run wires in 8AWG versus 10AWG and then price it out both ways…

Also, if you are going to run more than 3 current-carrying conductors in any single conduit, there is an additional derating factor, so be certain you are calculating current-carrying capacity of you home run conductors correctly…
good point i calculated for only one way! its really 200ft not 100ft. Hopefully i can change my order. Thank you
 
Not sure if your PV wire is rated for being submerged. (there are many different versions of PV wire and I don't know if you have rated wire for sitting in water). THHW is. (that is what the W in THHW is for)

When cable is in conduit is can always trap water so the wire have to be rated to be under water.

I am running the same 4x4 panel setup on 10 awg but with 305 panels....your amperage of 44 amps is to high for 10 awg.
Thanks for the reply. Im ordering the wire from temco. Its specd for water. i have 4 runs so each will have 11amps. So it should be good except i failed to calculate the return trip so i think i i need to go with the 8ga.
 
You will also need fuses or breakers at the panels. Breakers protect the wire and thus need to be at the point the power is coming from to protect the down stream wire.
 
You will also need fuses or breakers at the panels. Breakers protect the wire and thus need to be at the point the power is coming from to protect the down stream wire.
Good point i was thinking of putting them near the inverter but i need to remember the wires are a system component thats not cheap or easy to replace. Any recommendations on breakers or fuses?

thank you!
 
I ran wire in conduit for our first array and I don't think I would do it again, I think armoured TECK cable rated for direct burial is the way to go.
 
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