In Canada.
To find the maximum current a cable can carry the cable has a:
Base current rating,
De-rating multiplier depending on ambient temperature and the temperature rating of the cable.
The temperature rating of the cable is the temperature rating of the cable OR the temperature rating of the device being terminated to, whatever is less.
Victron does not seem to publish these ratings? Or do they and I’m missing something?
This would be the same issue in the US as well.
Thanks
Well, lukewarm is OK, but no hotter.
Put another way, anything above 40 degrees is critical! That’s why checking it with a thermal imaging camera is important.
The terminals will need tightening again later anyway if you’re running it hard at the limit!
All the tech specs have a rating for 25°C and 40°C.
For example this statement from an mppt manual…
Operating temperature
-30°C to +60°C (full rated output up to 40°C)
The full rating being whatever the device you are looking at is the rated current
Operating temperature is not necessarily the thermal rating of the terminal.
You can have a thermal rating of 90 deg C, but electronics that don’t want to see above 40 deg C. It has to do with how fast you derate the cable current capacity.
Its Rule 4-006 of the Canadian code book, and I think Section 110.14(C) in the US code.
Understood, but you don’t want the cable to be that hot. It means it is undersized, lol.
The operating temperature is all that is published. So from the code the default assumptions can be made.
MultiPlus II manual: It calls for copper DC cables with a 90°C insulation rating. That’s a cable spec, not a terminal rating.
And I think I read somewhere on the forum where a user was getting a terminal over temperature warning on an mppt at terminal of (DIY measured) 90°C. Not surprised as that is out of operation temperature range
As was already mentioned you don’t want anything getting that hot in normal running anyway
Good afternoon,
Well, I have never seen nor my colleagues burned connections of inverters we installed.
As said before, the connectors are certified for the current, so that’s off the question.
What is, are the cables itself and how to “crimp” the end lugs to them.
That has to be done with certified crimping tools, like, AMP, Weidmuller, hydraulic for bigger ones, etc.
All these tools let a special marking (from the company itself) in the lug, so it can be seen that these were done with certified tools…
And thats the main issue, if that lug is not making contact enough, then all will burn into plieces around it.
Then, before mounting a lug to a screw terminal, polish it with P400-800, and clean everything with electro cleaner, use these thin rubber gloves to not let human grease make it dirty, and place a flat washer below and above the lug and the spring washer under the nut or bolt head, that’s how it’s done properly.
Then, in each manual it’s clearly written what size cables to use.
Regards, Jeroen.