I didn't see anything in the manual that mentions ferrules (although the manual does have a graphic that might indicate ferrules if those yellow ends of the wire are an indication), and opinions online seem to be all over the place. Right now I'm leaning toward not using ferrules because it's 7-strand PV wire, but I really have no idea. I have the ferrules and the tool, just don't know whether it's best practice in this case to put ferrules on or not. Many thanks for any thoughts!
I wouldnt use 7 strand cable.
https://www.victronenergy.com/media/pg/SmartSolar_MPPT_RS/en/safety-instructions.html
Oh great. We ordered 2800' of this stuff and had it shipped to Alaska. It wasn't cheap. Had no idea that there would be any issue with 600V rated direct burial PV wire.
If the reasoning is the "contact area" as the manual appears to suggest, then wouldn't this solution work?
I would think that this MIGHT just transfer the issue to MC4, but if the wire is specified as compatible with an MC4 connector, then yes, 7 strand solar to MC4 and then MC4 with fine strand to MPPT would be a solution.
Sounds like this will be my approach then. Use the CB to transfer over to the approved wire for the charge controller for the positive wire, then MC4 to transition for the negative wire.
@AlaskanNoob are you going to have a PV breaker next to the mppt?
Seems like an obvious place to switch wire types.
Make sure that the breaker's clamps can be used with your 7 strand cable.
But it's a single pole, so it would just be the positive wire going through it. So I'm still going to need to figure out how to get the negative to switch over before going into the MPPT (I think) so I will explore MC4 connections to make that transition.
Plus an MC4 for 8 AWG wire perhaps will help me find some wire that has the number of strands required, so far the largest number of strands I've found for 10 AWG is only 19 strands.
But it's a single pole, so it would just be the positive wire going through it.
That's kind of dangerous.
Imagine your + PV cable gets damaged and is leaking to earth. Now your - PV cable is - 450v in reference to earth. That's quite a spark should you disconnect the - cable from the mppt. Quite a heart stopper should you touch the - cable.
Ferrules are not to be used with Victron MPPTs.
Thank you so much for this clarification. It's great to get it from Victron rather than dueling opinions elsewhere on the internet!
Ferrules make for a much neater installation, but they limit the contact surface area.
In some cases this isn’t an issue, but in others it can be.
A square crimpted ferrule will be better than a loose round one over thick stranded cable, but all will be inferior to fine stranded cable inserted with care and then torqued correctly.
Failure of an MPPT due to insufficient contact at the terminals is all too common unfortunately, though many MPPTs are also installed without optimum contact and without issues as well.
Best practice is a clean job, with fine strand to spec, and maximum contact surface area.
Would love to see these resources when you make them, especially if they show how to insert the cables correctly and any ways to measure or confirm it's been done correctly. If the resistance is the issue, it would be great to measure that if possible for peace of mind. We'll have 8 trackers getting 400V or so, in the middle of a large forest, and there is no fire department so anything you can make to help us get this right would be greatly appreciated!
Also, I had read that fine thread wire going into the terminals was more likely to have a thread break off and cause problems which makes sense so I suppose that is part of why you mentioned inserting with care. If there is any way to tell/confirm that inserts were done properly and no threads were broken that would be great. I suppose a way of securing the wires so they don't get tugged after the install and brad a thread might also be in order?
Wiring should always be mechanically supported so there is no stress on electrical connections. That should not be debated.
The ferrules issue often is but with the rising clamp design and the use of fine strand it is not necessary on the Victron equipment.
We ordered this 10 AWG PV wire that should meet the strand specs (87 strand) for use with the MPPT RS:
I see ferrules covered on page 28. I don't see where it says they are highly recommended but it does say "Use these if you are after a tidy wiring job."
@Guy Stewart (Victron Community Manager) says above that they should not be used with Victron MPPTs. Perhaps the Wiring Unlimited guide needs an update?
yes
i always use ferrules for most of my connections
We’ve been digging into this issue a bit on the diy solar forum. Maybe a sliding gate grip does better without a ferrule. But the documentation and guidance on what wire treatment is appropriate under what circumstances is lacking in the product specific Victron documentation. Surprising for Victron to fall down on this important detail.
Any chance for some formal guidance to include a consult with the engineering staff?
See: https://diysolarforum.com/threads/source-to-buy-quality-wire-ferrules.60670/">https://diysolarforum.com/threads/source-to-buy-quality-wire-ferrules.60670/
