I’m going to order one, what size do you run?. That fuse is blue sea. Apparently the T-fuses where hard to get for a while, so theses where the next option. looks like they are available now.
this is a Victron distribution box/buss bar, it should be good.
I’ve been tracing the heat source, it seems like it’s the switch (10% hotter then anything else). I guess I’ll order another one. It ran at 110 with the bypass wire. That’s good I think.
but the 4/0 to the inverter is getting hot at its 300A fuse. 140 degrees at the fuse, it’s a Victron fuse. Maybe I need a 400A.
I don’t have the clamp voltage checker.
I also don’t exactly understand what size fuses I should run ?.
my wire is 4/0 Temco easy flex welding cable, it’s not cheap, it’s -50% C to +105% C (221% Fahrenheit) the inverter wire now is hitting 140%F, so I’m in spec with that I guess. But the 165 at the shut off switch is still in spec but just seems to hot.
it would be nice to see what other systems actually run, wire hot wise under a ac load. Thanks for the input.
Well when I run my AC in the motorhome for hours and hours on end, my cables get decently hot too (12v systems run the highest current to get the same watts). I run a Magnum 2800w inverter, and use two 2/0 wires running parallel from middle basement to backend engine compartment, and have the old Blue Sea Systems 5002 fuseholder which I believe is discontinued now (where I have a 350a Class-T Littlefuse). I liked that 5002 fuseholder best because it had 3/8" diameter bolt mounts in it, with the big heavy block lugs on it. Now I think they replaced it with 5502 which is cheesier to me, thinner block lugs on it. Might just make my own next time if I need another one for a high current 12v application again.
With 12v, going up to 3000w-ish, no doubt things get hotter when running close to limits, I have two 250|100 charge controllers, those are baking every day at full Sun, the wires going out of them to the bus bars are hot, the wires going to the inverter are hot, the inverter is baking (when AC is running inside).
One day in August on 100° F day, I checked the temp of my inverter on the remote inverter screen, and found I was only 4° F from hitting max temp spec limit (fans were screaming), so I wound up putting a box fan outside a few feet away blowing into the inverter compartment to help the heat accumulation in the compartment (I always leave the compartment door open when AC is running), blowing cooler outside air better into the compartment.
I also keep a fan running all day blowing against my charge controllers as well. They are still all within spec, but they sure feel hot when pegged at 100a each for hours.
I am not saying whether you have a problem or not, but just suggesting that some of that heat might be normal, 250a-350a is a lot of current.
Since you have the Multiplus II, another option is to try using 2 inverters in parallel (stacked), so it splits the load and the heat will distribute better as well, each device and cable run will produce lower temperature.
Oh and on fuse size, remember that the fuse is always to protect the cable from meltdown, but also large enough to meet the demand of the inverter, so on mine, in my manual (for Magnum anyways), they publish a max current draw on DC side, so I made my fuse a bit bigger, but small enough as I could get away with to protect the cable (mine is essentially 4/0 since I have two 2/0 runs around 14ft, going to fuseholder then a 5ft chunk of 4/0 going to the inverter from the fuseholder), so I chose 350a Class-T fuse for mine, always holds the load, right up to inverter overload shutdown.