How to mount the Modular MEGA stacked fuse holder and bus bar correctly together

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dayandnight asked Apr 3, '20

How to mount the Modular MEGA stacked fuse holder and bus bar correctly together

Hello!

I worked today the first time with the Victron stacked fuse holder and the bus bar.

I am confused how to mount the stacked fuse holder with the Victron busbar. By dismounting one "screw stack" I got the screw M8, 1 pc. of wave washer, 2 pcs. of washer, 3 pcs. of nuts.

First question: Is it stupid to think the cable itself has to be fixed in a way that it can't accidentally jump off when changing a blown fuse?

Second question: Is how to mount the whole puzzle in combination with the fuse, cable lug and busbar?

To mount it as it can be seen on the Victron leaflet, seems to me at the first idea not correct, because than it is not possible to use the cover anyway.

So I tried first to mount it on top of the busbar.

By doing so it is not possible to mount the fuse 100% horizontal, because the thickness of the washers, nuts, cable lugs are not equal so at the end the fuse is some how crooked. And I feel not sure if it is perfect in sense to get the most possible contact from the fuse to the screw - busbar - nut - cable lug. There is always as contact surface "only" a washer, which is somehow smaller as the fuse and smaller as the cable lug. And it looks with all the nuts, washers etc. in the best way of thinking strange.

Therefore I tried the version to mount it under the busbar.

With this version it looks for me quit good. The fuse has a wide and 100% contact area from fuse to busbar and from fuse to cable lug. Still the fuse is somwhow crooked and not 100% horizontal. I don't care about this really. But I wonder there might be somehow some unwanted torsion onto the fuse, itself by this. Or doesn't this matter? And when dismounting the fuse when it is blown the cable lug is loose, too and it can "jump" off at an unattended moment and cause unwanted problems ... Is this the price you have to pay when wanted to get as much contact area as possible? And still I see no way to use the cover.

As I couldn't find any answers for my question at Victron, I hope to get some feedback here.

And last question. What maximum torque I should use to tighten the nuts?

I am looking forward for your ideas and thinking how to get the best and safest way of fixing all correctly together.

Kind regards and stay healthy

DayAndNight

fuses

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dayandnight answered · Apr 05, 2020 at 10:26 PM

Hello @Mark

thank you for your information about Victron Lynx-distributor. Very interesting. Meanwhile I found a very good solution which works perfect and the best is, that the fuse is on top and it is not neccessary to remove the cable lug when replacing the fuse.

When using the pieces which come with the fuse holder I found a way to stack the pieces in way which is just nearly perfect.

At the side of the bus bar the level / height for the fuse is 10,6 mm and on the side for the cable the level / Height is 10,0 mm. I think this "half-millimeter" is no problem, at all. To make it perfect it can be used instead of one M8 nut (height 4 mm) in combination with one washer ( height 1,6 mm) only one M8 nut DIN 936 which has a height of 5,0 mm.

I did one additional modification and used at the bus bar a 16 mm wide washer which fits perfect between the screw and the housing of the fuse. The housing of the fuse has a round shape and offers the necessary space for this. I think this wider washer offers more area to contact to the bus bar better.

For the side of the cable lug I used the washer which was delivered. I was afraid that the distance to the next pole/fuse is to small in case when replacing for example the fuse and working there with tools.

Hello @kai, thanks for the tip for Bluesea. I didn't know them and the offer interesting products.

One question I still have. Does anybody have a recommendation what kind of torque I should use to fix the nuts?

Thanks for help.

DayAndNight

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Modifications Space

Node Red Space

Answer 1 · 2020-04-04T02:35:23Z

Mark answered · Apr 04, 2020 at 02:35 AM

The bus bar goes on the top side.

As the bus bar is 5mm thick, I recommend to remove 1 nut and 1 washer from that side - 1 nut and 1 washer is ~5.2mm thick combined, so the height on both sides will match.

Accordingly, I would also install the cable lug on top of the fuse terminal. Yes this unfortunately means that you need to remove the cable lug in order to replace a fuse.

The related datasheet pdf has some images that may help.

https://www.victronenergy.com/upload/documents/Datasheet-Modular-MEGA-fuse-holder-and-high-current-busbar-EN.pdf

Lastly, my general recommendation is to use a Lynx distributor for this - they are a bit neater, provide a negative buss and not that much more expensive in the end.

https://www.victronenergy.com/dc-distribution-systems/lynx-distributor

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Answer 2 · 2020-04-05T04:12:17Z

kai answered · Apr 05, 2020 at 04:12 AM

For the product you're looking at, there was a compromise baked into the product design - use of shared mounting posts.

As Mark indicated, other products like Lynx distributor, or the class T fuse blocks from Bluesea, have independent mounting posts/mechanisms for fuse and cable lugs.

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