Electrical project underway

"HammerheadFistpunch" (hammerheadfistpunch)
10/24/2019 at 19:04 • Filed to: Electrical, halp, im hopeless

Finally getting around to doing my electrical sub panel in the cruiser. its been a LOOOONG time coming and my additions to the system are making it a necessity.

My plan is to use this

Which is a dual panel fuse board. 6 circuits on A and 6 on B. Common ground bus and separate positive busses. This lets me assign some stuff to a circuit that is energized from a relay tied to my ignition hot, and some tied straight to the battery.

I’ve figure out mostly what Im doing in terms of wire, terminals, relays, switches etc but I still have some questions I was hoping to get help with.

1. Bluesea says that this block is maxes at 100 amps total, 30 amps per circuit (per fuse). I was thinking about having a single 4 awg wire come in from the battery to Bus A and then an 8 AWG wire from the BUS A terminal to the relay that will power BUS B. So all the current would hit the BUS A post, but it wouldn’t stay there nor would it exceed 100 amps. Would this be safe? Alternatively i would bring in 2 x 8 AWG lines from the battery and run them separate. Plan A is cleaner and makes my goal of having this entire fuse system as self contained as possible. The BUS studs are #10 - 32

2. I plan on having at least 2 relays in a box with all the fuses. My goal would be to buy a waterproof box I can seal up this system with glands. Bad idea for heat? Something like this

!!! UNKNOWN CONTENT TYPE !!!

I would fab up a bracket for this and coming out of it would be 12 x 14 awg wire with weatherpak connectors and 2 large gauge wires headed to battery. Again the goal is that the box would be a new bracket away from whatever vehicle I want to install it in.

3. anyone have another good idea for a box? I was thinking about raiding the junkyard for an OE box from something, but I would gut it and use the box only. Im a little concerned about the durability of a hobby box like this in my engine bay.

4. should I just ditch the box idea and do a plate?

another interesting option that I like is to just bring it inside

(in the drivers footwell near some computers like locker and cruise control)

5. Lastly, and this one probably sounds really stupid...whats the story on grounding? Does the return to the negative buss need to be the same gauge as the supply? is there a good reason I shouldn’t terminate the ground at the device (on the chassis or body) instead of returning it to battery? It would save me a lot of trouble (and wire) to not have to bring the negative back to battery, but I also don’t want to have bad grounds.

I could have gone with a !!!error: Indecipherable SUB-paragraph formatting!!! like SO many people have done (and its a GREAT solution) but I wanted it my way, with ATC sized fuses instead of the minis.

DISCUSSION (10)

The Snowman > HammerheadFistpunch
10/24/2019 at 19:44

3rd gen f body in RHD strange.

jminer > HammerheadFistpunch
10/24/2019 at 19:44

You’re good to ground at the box instead of running back to the battery, that’s how it’s handled OEM.

You might look at painless fuse boxes. They’re super popular in old jeeps, well built, easy to use and durable in mostly exposed use cases.

HammerheadFistpunch > jminer
10/24/2019 at 19:47

I currently have a painless fuse/relay box and while they are well made the wir e gauge is not sufficient for me. plus I’ve already ordered my parts. Critic al voltage drop

When I say ground I mean ground at the drain. i.e. if I have a 5 amp draw at the back of the vehicle, do I just ground there?

VincentMalamute-Kim > HammerheadFistpunch
10/24/2019 at 20:38

1. I assume you’ve got constant hot circuits on Bus A? And relay switched circuits on Bus B?

5. Ground at the box / each drain. Negative bus needs same gauge as supply - same number of electrons coming in needs to go out.

HammerheadFistpunch > VincentMalamute-Kim
10/24/2019 at 20:58

1. yes, though bus b will all be active when the car is running as I’ll have a single relay energizing that entire bus .

SilentButNotReallyDeadly...killed by G/O Media > HammerheadFistpunch
10/24/2019 at 21:32

1. Go the single wire but don’t forget to use a fuse or fusible link between the battery and the stud.

2-3. Heat shouldn’t be an issue so waterproof cable glands are fine. I’d be inclined to use a decent enclosure that one might find from a electronics retailer like Jaycar in Oz https://www.jaycar.com.au/ip65-sealed-polycarbonate-enclosures-light-grey-with-mounting-flange-115-w-x-65-d-x-40-h-mm/p/HB6213

Kinja'd!!!

4. You could do it on a plate but the box means you have less to worry about in terms of protecting components. Putting it in the footwell is fine as long as it doesn’t get in the way of ergonomics or passenger safety and comfort.

5. Ground it at or near the box using a short length of the same gauge wire. You can also ground each subcircuit at or near the point of use as well rather that using twin core for each subcircuit. Which option you choose comes down to convenience.

jminer > HammerheadFistpunch
10/24/2019 at 21:52

Yeah, I would definitely ground back there. Just make sure it’s not grounded to super thin metal. If the sheet metal is thin run it to the frame so give you a solid ground.

Painless use to make just fuse boxes but after you reply I looked and they don't make it anymore...

MiniGTI - now with XJ6 > HammerheadFistpunch
10/24/2019 at 22:29

You can do that but you should fuse for the 8 AWG wire (~60a) at the battery. Otherwise fuse the 4AWG (~100a) at the battery and then fuse the 8awg leaving the first fuse block. If you really need that much power it probably would be better to send to 8awg independently fused at the battery.

HammerheadFistpunch > MiniGTI - now with XJ6
10/24/2019 at 22:57

I have a 100 Amp breaker at the battery for the main load, and I was planning to fuse the 8 awg from Bus a to bus B. Either megafuse or another breaker.

MiniGTI - now with XJ6 > HammerheadFistpunch
10/24/2019 at 23:25

Sounds good