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Holders for blade fuses in powerbox

April 26, 2020 — BarryK

I posted yesterday about the start of wiring the powerbox, and a problem with using blade fuses at 20-30 amperes:

Originally, I had purchased this blade fuse holder 4-way box:

However, after watching the Redarc video (see above link), I became concerned. The Narva packaging has "Maximum 30A per circuit", and if you believe that, then you could put a total of 120A through it, 30A per fuse.

I did a bit more reading on the topic, and it looks like the 6.3mm spade terminals, as used in the above Narva fuse box, are only designed to handle 10-15A. A 6-way blade fuse box sold by Jaycar, which, apart from having 6 slots looks identical in its internal construction to the Narva box, states "15A/circuit max" and "45A/block max":

Jaycar have these female spade terminals, rated at 10A maximum:

Comparing different blade fuse holders and spade terminals, some are thicker metal, and appear to be designed to handle higher current.

Looking at what blade fuse holders are on offer, some indeed are thicker metal and grip the fuse more firmly. I bought two of these inline blade fuse holders:

...these have superb grip on the fuse, and actually require some force to fully insert the fuse. Good, but I want to mount these on my "wiring-board". That board is 150mm horizontal by 170mm vertical, 6mm thick marine ply, and I posted a photo of the start of wiring it in the previous blog post. Here is a photo with two of the inline blade fuse holders mounted on the board:


...overkill using that heavy-duty fuse holder for the 1A fuse. To mount these fuses on the board, I used Selleys "All Plastic Fix" glue and a small piece of plastic cut off a chopping board.

I have used that Selleys glue on previous projects. It consists of a primer-stick and an adhesive tube, and will glue all types of plastic, giving a very strong bond. The primer-stick lasts a lot longer than the adhesive, and I was reading somewhere, someone just used superglue and it worked the same as the All Plastic Fix adhesive tube.

The 1A fuse goes to the coulometer, via the shunt. The 15A fuse will go to the cigarette-lighter sockets. I still have to put in fuse holders for the DC-output black Anderson plug, and for the solar input grey Anderson plug -- these will be 30A and 25A fuses. 

EDIT 2020-04-26:
Fuse holders for the 30A and 25A blade fuses have been added to the board:


I wanted screw terminals, so chose these:

These blade fuses need even more force to insert than the other ones, so it is a very good connection between fuse and holder, so I am confident these will handle 30 amperes. The screw terminal holes look like they will take up to 9 AWG -- I have just noticed that the table here has the wrong area for 9 AWG cable -- it should be 6.6mm2.

Same construction, the two fuse holders have been glued together for mounting on the board. Given the force to insert and remove fuses, I put an extra piece of chopping-board plastic to more securely bond the two holders together.

The two red cables going out to the left, have Anderson plug lugs on the ends, for insertion into the black and grey Anderson plugs.  

Tags: nomad