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How to properly extend solar wires


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I recently replaced my inverter due to space constraints slightly moved the inverter, requiring me to extend my 4mm2 PV wires. There was previously no joint required in the wires, and wanting to keep the wires in the conduit, I decided against using MC4 connectors just to extend them by 1 meter. Instead I opted for crimp ferrules which are properly crimped using a crimping tool and wrapped them in insulation tape and then covered that in heatshrink. But I'm questioning now whether this is the proper way to do it. Also, I noticed the ferrules state they are tinned - does this mean they should be soldered instead of crimped? 

The crimp definitely keeps the wires in the ferrule and tugging on it doesn't pull it out, but the crimp doesn't apply nearly as much pressure on the strands as MC4 crimping tool would. How do you guys extend them?

COPPER CRIMPING FERRULES THREE D AGENCIES] Multimeter, Heatshrink, Cable  Ties, Cable Markers, Cables Accessories | Three-D Agencies

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3 minutes ago, FixAMess said:

Mine were done like you did yours, but in hindsight I'd rather have used a mc4 connector.....Just because I hate electrical tape!

Did you also just crimp them, or did you use solder?

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Just now, FixAMess said:

Just crimp....

I'm thinking of sandwiching a little plastic box in the conduit where the current joint is and rather use MC4 connecters inside the box to join them. That said, I'm not sure if MC4 connectors actually have higher loss than crimp ferrules.

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If it's inside the house, in a conduit, I think most electricians would just use ferrules and tape. They'd probably only use heat-shrink if you were standing there watching them! 

Remember that the MC4 connector will have a crimp both sides as well as sliding contact between the plates, so a single crimped connection will always be better than a pushfit connector. Once crimped, the wire acts as a "single conductor", since the crimp deforms and almost cold-welds the copper strands together. There's no need to solder, it shouldn't be able to get into the joint if you've crimped correctly. 

Your only concern should be if your insulation has a high enough voltage rating for the PV string, but unless you've gone out of your way to find the cheapest tape and shrink insulation, I'd guess it's fine. Even just using "an MC4 connector" doesn't save you from this consideration - you may need to specify the high voltage (1000V or 1500V) connectors if you have a 600V+ solar installation... Some of the MC4 connectors are only rated for 600V.  

Personally I like to use insulated crimp connectors - they're faster and usually have all their voltage ratings and compliance information written right on the packet.  

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Much ado about nothing.

The correct sized ferrule, using a proper crimp connector - rachet type is best.

Then a single shrink sleeve with 20mm excess on each side of the crimp is more than enough.

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6 minutes ago, Adri said:

Much ado about nothing.

The correct sized ferrule, using a proper crimp connector - rachet type is best.

Then a single shrink sleeve with 20mm excess on each side of the crimp is more than enough.

What I've done is to offset the joints along the cable by a few centimeters. Still properly insulated and heatshrink applied, but now virtually no chance of contact 
image.png.79be8cd1166d2b38fe1a661a894a26f7.png

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1 hour ago, recre8 said:

What I've done is to offset the joints along the cable by a few centimeters. Still properly insulated and heatshrink applied, but now virtually no chance of contact 
image.png.79be8cd1166d2b38fe1a661a894a26f7.png

Great! don't let it keep you up at night then :)

Unless...... 🤔

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One thing to keep in mind is a ferrule joint should rather be done inside an accessible junction box for future inspection or fault finding and not in a conduit where it cannot be seen or inspected. I prefer ferrules tightly crimped, taped up and heat shrinked  for extra protection, it should be sufficient for years to come. Soldering is not recommended for ferrules as it will change the integrity of the ferrule to conductor it can become loose or even form cracks with time.

When using MC4 connectors make sure you use the same brand male to female connectors because the different brands are not 100% compatible and can cause loose connections. 

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I understand that MC4 connectors are designed and made for outdoor use. They don't make sense indoor. The installer of my PV panels used the factory fitted ones only for interconnecting the panels in series. On the feeder ends he cut them off and spliced the extension wire with insulated crimp ferrules in such a way to them that the splices got inside the roof.

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