Hello,
A regulatory question regarding the Consuel inspection:
With two 70 mm² cables per pole between the Mulitplus and the Lynx, do I need four 200 A knife-blade fuses, or
two 400 A knife-blade fuses?
I’ve found both answers online.
Thanks
Kind regards,
My local distributor suggested I could do either
a) join pairs of cables onto the same studs of a 400A fuse holder or
b) run each cable separately through its own 200A fuse holder.
I chose option b) for two reasons. 1) because I don’t like the idea of stacking lugs on a stud and 2) because the short 70mm cables are very stiff and don’t bend easily so having separate paths was easier.
ps. I’m not in France so no need to fuse both the +ve and -ve cables.
Hello,
Just to clarify, the knife switch disconnector allows two cable lugs to be screwed onto each pole without stacking them.
Kind regards,
Datasheet mention 2 x 50mm2 per pole on Multiplus II 10000, your cables are well oversized.
The fusing requirements are 2 x 200A on positive only.
Generally, negative pole is not fused or interrupted, especially in 3 phase systems.
For inverter side, you can install 2 x 200A/80V MEGA fuse in Lynx Distributor. On the battery side, NH0/NH00 is perfect as fuse and disconnector.
If want to keep the existing inverter disconnector with blade fuse, will need 2 x 200A fuses.
The question needs to be phrased differently to find the answer.
The real question is how much current my cable can handle.
If it can handle 400 A, then one fuse for both cables is enough. If it can handle less, each cable will need its own fuse (not taking into account the various correction factors required by the standard).
As for whether or not to protect both poles, that depends on the local standard. If we’re governed by 712-2 or 712-3, two-pole protection is generally mandatory.
Hi, connecting cable lug to cable lug only works if the lug can handle the total current.
With 70 mm², that’s more like 160 A (in 230/400 V AC systems).
So you’d be better off using 160 A per string: NH fuse-switch disconnectors are slow-acting, so even at full load and with a slight overload, you’ll still have some time before the fuse blows.
400 A would normally require 240 mm². Here, you’ll need to check the specifications for the cable type to see what it can handle. That way, you’ll be on the safe side.
Hello,
Sorry, I wasn’t clear enough.
The installation is in France, as it has to be inspected by Consuel.
Then, both the positive and negative poles will be disconnected.
The Victron documentation mentions 2 x 50 mm2, but I had 70 mm2 cable, which I used.
The question is: is it permitted by Consuel to use a knife switch with 2 x 400 A fuses for 2 x 2 cables?
Two positive and two negative 70 mm2 cables run from the MP+ 2 to the switch, without stacking the cable lugs,
then run on to the Lynx, again without stacking the cable lugs.
Thank you for your help.
Kind regards,
4 cables must arrive at the isolator. The protection must be double-pole.
Permitted: I would say YES if all 4 cables arrive at the isolator (whether or not the lugs are stacked). I’ve already seen several installations approved with two lugs stacked.
Properly protected: I agree with Thierry’s view. There is a risk that one of the two cables (or wires) could be damaged, disconnected, … forcing the current to flow through only one cable.
For the fuse rating: Wirl’s point is valid. NH fuses are time-delay fuses. They won’t blow at 400 A immediately, but after a few seconds, minutes or hours, depending on the overcurrent. Will the wiring withstand the overcurrent for long enough for the fuses to blow? That’s the question.
In your case, a knife switch with two NH1 250Ah fuses seems sufficient to me. For safety, you could protect each cable individually by adding two knife switches with NH00 125Ah fuses.
That way, power peaks of up to 400 A should be able to pass without blowing the fuses, as they are short-lived.
Hello,
I can only provide the information from our own business:
Cable lugs: if you want to carry 200A per cable and the cable lugs are stacked on top of each other, the “lower” one must be rated for 400A
France/Germany: I’d say the technology is the same. Under the new German standard: continuous load for NH00: 125A, that’s definitely fine. 160A is also fine if you know for sure that the average continuous load will be no more than 80%> that’s how it is with commercial “installations”
NH1 goes up to max. 250A → continuous load approx. 200A, NH2: 400A — continuous load: 355A fuses are also fine, NH3: 630A → 400A continuous load is no problem
If you use a self-protected cable from the Multiplus to the fuse, choose a short one, then you can also use a smaller cross-section. After the fuse, size it appropriately!
Space could be a problem for you: NH00 is much smaller
Since there is only one connection bolt on the Multplus 2 — or are there 2 bolts? With one bolt, using 1x240qmm NSGAÖUF isn’t ideal; with 2 bolts, 95qmm each is enough for 200A. I think you have 1–4m
The current-carrying capacity is much higher than the cable’s fuse rating. Check the cable type’s datasheet.
Remember to grease the contacts and, if possible, do this with no load; otherwise you’ll get marks on the isolator/fuses, which can lead to overheating, etc. That’s not good.
Question: how did you arrive at 400A? If I calculate 10kW / 48V → approx. 210A → max. peak → doesn’t matter → surely 1x 95qmm or 2x 35qmm is enough → although, if you calculate it, perhaps just 2x25qmm. I’d need the cable length and cable type for that.
Regards
Hope I haven’t caused any more confusion.
Please could you explain how to use this table. I can’t get my head around what it’s trying to convey.
Thanks 
At the top, cable cross-section from left to right; amperage downwards:
If your cable is 23 m long and you want/need to protect it with a 20 A fuse, you’re looking at 10 mm².
If you want to protect a 23 m cable with a 40 A fuse, I’d go for a cross-section of 16 mm². According to the table, it would be 25 mm².
Clearer now?
Regards
I think you are saying that the dimension of the numbers in the body of the table is length, in metres, to two decimal places.
If that’s right it would be handy for @macloof to include it in the screenshot. It’s the missing bit of information that was confusing me.
And are we saying that those are recommended cable gauges to use, or does the table just represent theoretical minimum gauge / maximum length?
