Solar Panel output Splice box

mkgrady

Senior Member
Location
Massachusetts
I’m doing my first job that involves a solar panel so I am a total rooky with a question.

The job has one solar panel with about a 40 volt output. The panel comes with a negative and a positive output wire with some special pre-made connectors. The panel feeds a battery and charger system that goes on to feed a heliport lighting system. The solar panel, battery/charger and lighting controller are all mounted within a few feet of each other on a fence that forms the perimeter of the landing area. Most things seem pretty straight forward except for the wiring between the solar panel and the battery/charger. The solar panel has a positive and a negative wire with each having a special looking connector on the end.

My question is about how to extend these leads to the solar output to the battery/charger. I’m picturing these DC wires being run to a pvc junction box and spliced on to thhn/thhn wire run in pvc conduit back to the battery/charger. I’m not sure how to have the solar output wires enter the pvc box. Can I just drill two holes the size of the insulated wires?
 

mkgrady

Senior Member
Location
Massachusetts
I would use an appropriately sized compression cord grip. Or you could install matching connectors, but I'm guessing you don't have the tool and don't want to buy one.
I don’t know what that tool is so I probably don’t have enough call for it to justify a purchase. I don’t even know what I would buy. I like the idea of a compression connector for the solar output wires but can’t imagine I can buy a connector that would squeeze down small enough to hold a cable that looks to be between 1/4” to 5/16”. Is this a common connector?
 
I don’t know what that tool is so I probably don’t have enough call for it to justify a purchase. I don’t even know what I would buy. I like the idea of a compression connector for the solar output wires but can’t imagine I can buy a connector that would squeeze down small enough to hold a cable that looks to be between 1/4” to 5/16”. Is this a common connector?
Yes any supply house would have.

The solar panel connectors are called MC4 (usually).
 

mkgrady

Senior Member
Location
Massachusetts
Yes any supply house would have.

The solar panel connectors are called MC4 (usually).
Thank you. I looked them up but the MC4 connectors seem to be a way to extend the solar panel output leads, not a way to enter a junction box. I think I’m looking for a way the splice the solar leads in a box in order to extend them to the lighting controller panel. I guess I could just extend the solar leads all the way to the controller but I still need a way to enter the enclosure. I just thought getting the solar leads in a junction box and extending those leads with a splice, pipe and thhn would provide more protection.
 

jaggedben

Senior Member
It used to be that solar suppliers would sell you, say, a 50ft conductor with a positive and negative MC4 on the ends, so you could cut it in the middle and extend your panel leads, say, 25ft to your j-box. I'm sure that's still out there somewhere. If this is just a one off you might still be able to find that for cheaper than buying an MC4 crimper. Then again, the crimpers are maybe $50-75 online now. Use PV wire or USE-2 if you crimp you're own.
 

mkgrady

Senior Member
Location
Massachusetts
It used to be that solar suppliers would sell you, say, a 50ft conductor with a positive and negative MC4 on the ends, so you could cut it in the middle and extend your panel leads, say, 25ft to your j-box. I'm sure that's still out there somewhere. If this is just a one off you might still be able to find that for cheaper than buying an MC4 crimper. Then again, the crimpers are maybe $50-75 online now. Use PV wire or USE-2 if you crimp you're own.
I have located a conductor with the ends you describe so now I don’t need to have a junction box and conduit with thhn to reach the battery enclosure. Now, how do I have these conductors enter the controller enclosure. Is it just a compression connector that uses a 1/2 knockout for each wire? Any idea what this connector is called?
 

CajunTech

Member
Location
Watson, LA, USA
neutralizing the pv energy

neutralizing the pv energy

I’m doing my first job that involves a solar panel so I am a total rooky with a question.

The job has one solar panel with about a 40 volt output. The panel comes with a negative and a positive output wire with some special pre-made connectors. The panel feeds a battery and charger system that goes on to feed a heliport lighting system. The solar panel, battery/charger and lighting controller are all mounted within a few feet of each other on a fence that forms the perimeter of the landing area. Most things seem pretty straight forward except for the wiring between the solar panel and the battery/charger. The solar panel has a positive and a negative wire with each having a special looking connector on the end.

My question is about how to extend these leads to the solar output to the battery/charger. I’m picturing these DC wires being run to a pvc junction box and spliced on to thhn/thhn wire run in pvc conduit back to the battery/charger. I’m not sure how to have the solar output wires enter the pvc box. Can I just drill two holes the size of the insulated wires?
On a note of safety, always cover the pv module with something to block sunlight from reaching surface when working during the day. Then validate energy condition by either measure for zero voltage on open circuit condition or measure amperage with an amp clamp for closed circuit condition.
 
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