What would you do?

"HammerheadFistpunch" (hammerheadfistpunch) 10/14/2020 at 16:53 • Filed to: halp, wiring again?

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Im trying to figure out some wiring (again). I have my sub-panel how I likes it, and I just upgraded the main feed lines from 8 AWG to 4 AWG so I feel very happy feeding the sub-panel more amps that my alternator could possibly supply.

So I got my sub

Woo! I can’t tell you how long this has been coming. So now I have a decision to make for wiring. I did the math and I need 20 amps of capacity which means 8 AWG wire (at the distances involved) which I have, though my 8 awg lugs aren’t my favorites (too big a hole). Anyway, here is the situation. I have 4 paths to get the power to the sub.

1. Run it straight from the Circuit breaker (100A) that feeds the sub panel and then fuse at the source.

Pros - simple

cons - the whole point of the sub-panel was to consolidate electrical and reduce extra wiring all over.

2. Run it off the sub-panel from the A circuit, which is battery hot straight out (fuse on sub-panel)

Pros - ideal, the panel can handle 30A/circuit, though only 100A total. Granted the whole thing is on a 100A breaker so Im not worried about melting the panel.

Cons - I would have to rewire some other things on the circuit as all slots are full.

3. Run it into A Circuit then into a relay triggered by the ignition, its a small Zhong Tong mini NO 30A relay, so it can handle the current but the wiring in and out is 12 AWG. I could size up from the output to 8 but I feel like that’s a bad idea.

Pros - no sneak drain when the power is off

Cons - wiring is far from ideal and I don’t know how I feel about running 20 amps through these little relays.

4. I could run it into B circuit which is run entirely off a NO 120 amp relay ignition triggered.

Pros - no sneak drains when the power is off, open circuit

Cons - puts stress on the B circuit which isn’t the more powerful of the 2 circuits. It’s on a 60A breaker and the 8 AWG connecting the circuits only really allows for 50 or so amps and I already have about 40 on there. I want to upgrade the wiring to 4 AWG but I don’t have the needed lugs. I can do a mix of 4/6 which would let me run up to the 60 limit of the breaker no sweat. there would be 60 fused amps drawn on B if I put it here. more heat through the 120A realy.

The sub and my stereo have a remote trigger so it can power off when the stereo does so I technically don’t NEED to have its supply ign triggered. But it would give me some peace of mind knowing there wouldn’t be a sneak drain when in the boonies. I don’t know how that would affect the sub long term though to be hard cycling each startup.

Thoughts?

EDIT: I upgraded the wire to 6/4 so now the B circuit can happily handle the limit of the breaker. I’ m still going to wire it hot off of A I think though.

If only EssExTee could be so grossly incandescent > HammerheadFistpunch 10/14/2020 at 16:58

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I'm a big proponent of not having battery hot electronics. The one-time effort of beefing up your ignition-switched circuits is significantly less hassle than getting stranded out in the woods somewhere.

Aremmes > HammerheadFistpunch 10/14/2020 at 17:01

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“Cerwin Vega”

5. Replace the sub-panel with a larger one.

RacinBob > HammerheadFistpunch 10/14/2020 at 17:09

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That’s funny, I am skimming this and reading that you are trying to wire from either your 100 amp circuit breaker or off of a 30 amp source. So I am thinking it is at 110 VAC, and damn, you got o ne hell of a subwoofer......

Oh, its for a car, nevermind.......

RacinBob > Aremmes 10/14/2020 at 17:21

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I own a cerwin vega for my home system..... Bought it new about the time that youngster made the above movie.....

The Snowman > HammerheadFistpunch 10/14/2020 at 17:30

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Wire it like the manufacturer intended with always hot power and a trigger.  Turning off audio gear by pulling the power cord out of the wall is a pretty quick way to shorten it's life. I have relevant experience in high end home audio and a bit of car audio experience. I have seen car amps break and then find a very bad ground cable so it's possible the persistent on off of the weak ground killed them. 

HammerheadFistpunch > Aremmes 10/14/2020 at 17:34

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ITs old stuff, but its the best rated, strongest and larg est sub that fits my setup. Hoping for good things.

HammerheadFistpunch > The Snowman 10/14/2020 at 17:36

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The ground would be a short 8AWG to chassis, so im not worried about that, but I do worry about hard cycling the amp.

HammerheadFistpunch > If only EssExTee could be so grossly incandescent 10/14/2020 at 17:51

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I also dislike battery hot, which is why only the stuff that needs to be is on circuit A (Fridge, some lights, USB, etc) and even then most of that stuff is still technically ign hot as it requires a trigger for the relay (auxiliary cooling fan, lightbar, etc) .

The Snowman > HammerheadFistpunch 10/14/2020 at 17:54

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Yeah my point is a bad ground creates the same situation with hard cycling. No bueno.