10/2 wire selection

[Off-Grid Sailboat]

Curious if there's a downside to using high quality marine grade tinned copper that is 10AWG 2 conductor (10/2) from panels to MPPT rather than single conductor cables. I'd prefer this as it's easier and cleaner for me to run 10/2 cable.

 

[Dzl]

Curious if there's a downside to using high quality marine grade tinned copper that is 10AWG 2 conductor (10/2) from panels to MPPT rather than single conductor cables. I'd prefer this as it's easier and cleaner for me to run 10/2 cable.

Whatever wire you buy, you want to make sure that the stretch between the panels and the SCC its rated for outdoor + UV. I would imagine that a lot of 10/2 is not outdoor rated since I think its main use is in interior branch circuits.

 

[Off-Grid Sailboat]

good point and thanks or the input! probably best to go with PV specific wire.

 

[Dzl]

good point and thanks or the input! probably best to go with PV specific wire.

Probably, I haven't found any ABYC specific guidelines for outdoor or solar wiring which is a little surprising to me, as they are pretty specific about most other things wiring related, and usually make it pretty easy to determine what environmental conditions specific wire types are rated for. But I haven't found any easy way to tell whether its outdoor/uv rated. For that reason, I think its safer just to use solar wire, unless you know for sure whether an alternative will fare well outdoors.

 

[RandyP]

Any 2/C jacketed cable will retain more heat then 2-1/C cables.

 

[erik.calco]

Whatever wire you buy, you want to make sure that the stretch between the panels and the SCC its rated for outdoor + UV. I would imagine that a lot of 10/2 is not outdoor rated since I think its main use is in interior branch circuits.

We should talk more about this on the forum because a few things don't add up in the market with this general PV recommendation. One is that I noticed that PV cable is always 10 AWG or higher. Why is it hard to find lower gauge PV? I've noticed it is common to put the combiner by the array, where you'll need to run lower gauge wire to the inverter from.

What if you are running underground through PVC? What's the best wire for that? It won't be exposed to UV or heat from the sun. Ideally, it won't even get wet if the PVC remains sealed, but it's fair to assume it might. Some run above ground through PVC, too.

What about indoor PV from combiner to inverter, typically heavier gauge like 2-4 AWG? For this use case, I went with marine tinned copper.

 

[Dzl]

We should talk more about this because a few things don't add up in the market with this general PV recommendation. One is that I noticed that PV cable is always 10 AWG or higher. Why is it hard to find lower gauge PV?

Taking a couple guesses (based on vague recollections) it might have something to do with MC4 connectors maxing out at 10AWG and/or thicker jackets (though I might be confusing this last point with marine grade 105*C wire, I can't remember).

What if you are running underground through PVC? What's best wire for that? It won't be exposed to UV or heat from the sun. Ideally, it won't even get wet if the PVC remains sealed, but it's fair to assume it might.

What about indoor PV from combiner to inverter, typically heavier gauge like 2-4 AWG? For this use case, I went with marine tinned copper.

Once your inside, and/or not exposed to harsh conditions, I would assume normal marine grade would be more than fine, and I would think it would be particularly well suited for underground, but I'm not positive, and not sure what the NEC or your local electrical code would require.

 

[erik.calco]

Taking a couple guesses (based on vague recollections) it might have something to do with MC4 connectors maxing out at 10AWG and/or thicker jackets (though I might be confusing this last point with marine grade 105*C wire, I can't remember).

You're right. And not disputing that recommendation. Just saying there is a lot that I haven't seen discussed well here (in the DIY forum), primarily running from combiner to inverter and different ways to run that. Though I have heard the amp limits of MC4s discussed. Even that isn't always the same number, and probably isn't the same if comparing cheap vs high quality MC4s. I haven't heard much in how people are resolving it.

Most individual strings are likely to be fine with 10 AWG PV. It's the rest of the run we haven't discussed in length, unless I missed the threads.

10 AWG can suffer too high of a voltage drop at higher amps that can be hit when combined. I wonder how RVs handle this with their branches near the panels, since the combined wire is still outside and exposed, but may need to be below 10 AWG.

 

[Dzl]

All good points

there is a lot that I haven't seen discussed well here (in the DIY forum), primarily running from combiner to inverter and different ways to run that. Though I have heard the amp limits of MC4s discussed. Even that isn't always the same number, and probably isn't the same if comparing cheap vs high quality MC4s. I haven't heard much in how people are resolving it.

Looks like the UL listing for MC4 is 20A 600V, so if you buy reputable UL listed connectors your should be able to count on that.

10 AWG can suffer too high of a voltage drop at higher amps that can be hit when combined. I wonder how RVs handle this with their branches near the panels, since the combined wire is still outside and exposed, but may need to be below 10 AWG.

Yeah this could definitely be an issue. On the one hand mobile installs generally have shorter wire runs, on the other hand they are more likely to wire partially in parallel so amperage would be higher. And since array size is limited, efficiency is probably more important.

 

[KenInNC]

I got 100’ for about $110 shipped. It’s 10/2 Anchor wire and it says it can handle UV. I read that the Marine Grade wire handles the amperage better as in it seems Underrated for its actually amp capacity but I could have read this wrong. The wire looks good. Here are the specs:

• Manufactured from individual copper strands and tinned to perform in the harshest marine environments.
• Ultra-flexible Type 3 stranding resists fatigue from vibration and provides added corrosion protection.
• Exceeds all UL 1426, US Coast Guard Charter boat (CFR title 46) and ABYC standards
• The premium vinyl insulation is rated at 600 volts, 105 deg C dry and 75 deg C wet, stays flexible even in extreme cold (-40 deg F/C) and resists salt water, battery acid, oil, gasoline, heat, abrasion and ultra-violet radiation

 

[KenInNC]

Beyond being tinned, marine cable is larger than say automotive cable at the same size. So, 6 AWG marine cableactually contains more copper than 6 AWG automotive cable. The more copper, the better the current carrying capacity of the cable. Marine cablealso carries a pliable and durable PVC jacket

 

[KenInNC]

Marine wire is larger for a given gauge size, up to 12% larger in some sizes. If you choose to use SAE wire, you must allow for this difference when using commonly available marine voltage drop tables.

 

[RandyP]

I think I have just figured out that there should be an equipment grounding conductor from the solar panel (s) aluminum base to the electrical system dc ground buss. And that EGC should be run in close proximity to the '+' and '-' wires from panels to solar controller. so 10/2 with an additional 1/C ground wire (solar panels on building structures, 50v or greater).

 

[Dzl]

I think I have just figured out that there should be an equipment grounding conductor from the solar panel (s) aluminum base to the electrical system dc ground buss.

Correct, or at least generally reccomended

And that EGC

EGC? Equipment Ground Connection?

should be run in close proximity to the '+' and '-' wires from panels to solar controller. so 10/2 with an additional 1/C ground wire (solar panels on building structures, 50v or greater).

Interesting, do you know the logic/theory behind that? Also excuse my vast ignorance but what does 1/C ground wire mean?

 

[RandyP]

Equipment Grounding Conductor ECG.
1/C One Conductor.

 

[RandyP]

Interesting, do you know the logic/theory behind that? Also excuse my vast ignorance but what does 1/C ground wire mean?

Here's the Code and explanation (2011 NEC, I'll check if the code text has changed for 2020 code; 2020 code is 690.43 C) with minor language change. )
Article 690.43 F) (of course this is for photo voltaic cells mounted on Buildings with output voltage > 50V, but I think its a good guideline to comply with).

 

[RandyP]

Equipment Grounding Conductor ECG.
1/C One Conductor.

OOPs, ECG should read EGC........