question

@denty I agree with you that just applying a 1.5 Nm torque looks too little.

But with practice I discovered that the effect of a torque applied to a screw clamping a wire changes drastically if you only turn the screw, or you also very firmly push it with the torque-limiting screwdriver while turning... It improves drastically the grip on the wire, drastically helping squeeze the wires, while sparing the screw.

A firm push while turning at up to 1.5 Nm has way more effect than turning up to 2.5 Nm with only a small push (except that at 2.5 Nm you don't have a choice than to push firmer to not damage the screw head).

So, yes 1.5 Nm turn without a firm push is sure not enough for a 10 or 16 mm² 40/50A wire, but 1.5 Nm turn with a firm push looks quite ok to me, even with the maximum 16 mm² crimped fine stranded wires.

Also If you have a wire with a few twisted large strands, make sure to untwist them, so they insert parallel for maximal contact area and a firm grip of all strands.

@Guy Stewart (Victron Community Manager) @mvader (Victron Energy) those 2 practician hints might be something for the manuals and your excellent wiring book. ;-)

I see. That makes sense. I didn't yet look at how the screw clamps work in the Multiplus. I'll take a look with an iPhone and close lens. But if it's as you suggest — that the screw clamp acts to provide downward pressure — then that could be a quite helpful trick.

I’m pretty sure it says 1.6NM in my printed Multiplus-II installation manual. Not much different to the 1.5NM you suggest. I’ve also seen pictures where people have broken the AC connector blocks off the PCB so don’t go crazy.

As another data point, the RCBOs on my consumer unit specify 1.2NM for the line and neutral connections, even on 40A shower and cooker circuits.

HTH

Thanks Craig.

OK. Maybe the 1.5Nm is more appropriate than I presumed. It’s reassuring to find it referenced elsewhere.

I’ll err on the more conservative side then.

It's indeed 1.6 Nm, specified in the manual.

The 8mm DC are 12 Nm max in the manual.

@mvader (Victron Energy) @Guy Stewart (Victron Community Manager) :

1. The MP-II manual does not specify Nm torque for the 6mm earthing ground connection of MP-II. My guess is that around 6-8 Nm is the maximum for 6mm.
2. Btw, that ground connection is a bit tiny and space below a bit short to affix a 35 mm² grounding cable (above 35 mm² cables, with recommended 70 mm² wires for DC for MP-II 5000, Swiss NIBT, based on IEC, specifies grounding jauge of 50% of largest conductor). Additionaly the small contact to the casing is most probably insufficient to match 35 mm² grounding jauge.
3. And last suggestion to Victron: it's almost impossible to mount crimped 70 mm² DC wires on a MP-II 5000 because of the limited space of their incoming holes, and nearly impossible to remove them if needed afterwards. An ovale, or larger hole, or less long 8 mm bolts on the MP-II would help a long way in mounting.
4. EDIT: ADDED: It would be nice to write maximum torques directly on the units themselves near the terminals. I always affix stickers with Nm torque and for connections max./recommended fuse Amps on them, which makes it easier for inspections. Fronius inverters have such markings and some Hager and ABB gear too.

Just to avoid any uncertainty over this, here are some photos of the manual in question and the page showing the 1.6NM figure.

However, this torque figure is not shown in the PDF or HTML version of the manual on the Victron website and I recall some discussion about that a while back on the forum. Not sure if anyone from Victron commented on why the manual was changed.

Ah! I found it… mine has 2 Nm.

Comparing your booklet with mine, it looks like someone hit delete and accidentally joined it to the end of an otherwise unrelated paragraph.

Also interesting to see it is a different value.

Thanks guys. Need to get my more careful reading glasses on next time.

d.