Rising Sun Ham Guru
- Jun 8, 2006
- Grand Junction
FYI, about Blue Sea fuse blocks. I have a couple, so it's not that I dislike them in full disclosure. But they say generally with these screw terminal block a maximum of 30 amps per circuit and 100 amps total. I've never been able to determine a clear answer whether they mean 30 amps true max or that's the largest fuse you should use. The two things are not the same.Hey this looks pretty slick and keeps everything at the battery. My battery looks just like @Notyourmomslx450 and I'm running out of room in the engine bay for a fuse box. I also need to run power to the cargo area for a fridge and what not. Following this thread closely.
I've taken it to mean that's the largest fuse you should use with them which means if you use standard ATC the actual maximum current is somewhere between 37.5 and 45 amps, depending on length of time (an ATC will hold 125% of rated indefinitely and will blow at 150% between 1 and 10 seconds). This is important to in my case since the shore charger I use is an Iota DLS-45, which can supply 45 amps (duh, from the model number). Iota fuses it with a 30A ATC, too, and I've a couple of times had a fuse open but the block itself never seemed to get warm so that's why I think it's a conservative rating based on fuse size. Can't say that for the PP45 connectors I was using (the SB50/PP75 is a better choice I find beyond 20 amps). At 45A they do get worryingly warm even though that's their stated max rating...
What was limiting, though, was running a branch from my head end engine fuse block. I used 8 AWG/105C wire that should technically be fine to 80 amps in free air and even still good to 68 amps bundled. So technically you could use a 60A fuse reasonably safely. But I still only use a 30A on it branching from a circuit on the Blue Sea. That limits the remote block (also a 100A total and 30A/ckt Blue Sea) to practically only 30A total. That kind of handcuffs the utility of that remote block to only small loads, which is OK for my use but might be a problem if you're expecting to run a couple of sizable circuits in that branch.
You could tap the supply screw of the feeding block (or even use it's own inline fuse, probably best at the tail end) rather than using a load circuit to supply the second block, so they are bus instead of branching topology. But that seemed like a confusing mess and that remote block in my case isn't under high demand. The only thing I've ever had as an issue was I couldn't use the DLS-45 plugged into the remote block without eventually opening a fuse.
The extra cable length seems to push it up for long enough to be a nuisance with a deeply discharged battery. But the reality is I chose 8 AWG run to the remote block mainly as it was a middle ground beneficial to reduce voltage drop enough without the cost of a 4 AWG that would be real overkill current-wise. I could have gone 10 AWG or maybe even 12 AWG to run my fridge since it's not particularly voltage sensitive.