emergency lighting and more e

Disclaimer: I'm not sure that this is the right section to post in, since my request for help spans several different topic areas. Mods please move it for me if I'm in the wrong place, or let me know where to repost it if necessary.
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I have long been using this site as a reference, and find myself now needing a little more assistance. I really want to do this right so I am turning to you all for help.

I have a truck that is being used more and more for responses as an emergency vehicle (privately owned) and need to upgrade the Mickey Mouse wiring job that has sufficed for the last few years – but was only supposed to be temporary. While wiring this all up, I would also like to consider future additions such as the desire for slightly more bass to my music and a potential inverter. I have never wired a sub nor an inverter, so I’m feeling a little edgy.

What I would like to do is run one fused primary lead from the battery for all potential uses and split within the cabin by use of a distribution block. I’m not certain what size power lead to run in. Also, can grounding be effectively achieved within the cabin, or is a run back to the neg terminal necessary?

I am trying to put together a shopping list of wire and accessories needed for this task.

The equipment that will be installed is as such:

Siren/Controller – The instructions call for a 50a 4awg input and a ground to battery of 12-20awg. It drives a 100w speaker and up to (9) 15a lighting circuits. As most of the lighting is LED, the chances of actually pulling 135 amps + the speaker is highly unlikely. Actual draw is anticipated to be 28.8a + the speaker (so 36.6a?).

Mobile Radios – There will be two, but I only have the specs on one. I am going to assume the second will be comparable. Current drain (approx.) :Tx 50W/45W 14.0A; Rx Max. audio 1.2A; Stand-by 300mA

The amp that I picked out has the following specs:
• Mono subwoofer amplifier with 1200-watt max power capability
• Delivers continuous 300 watts x 1 at 4 ohms, 600 watts x 1 at 2 ohms
• Variable low-pass filter crossover (40~240Hz, at -12 dB per octave)
• Speaker-level inputs for connecting to most source units
• 50Hz bass boost with remote level control (0~12dB)

And here are the speaker specs:
• 10-inch Shallow Series subwoofer with 1200 Watts maximum (300 nominal) power handling
• Basalt/carbon fiber reinforced IMPP cone with fiber-woven radial surround
• 4-ohm single voice coil design
• 20 Hz to 290 Hz frequency response with 90 dB sensitivity

With regards to the inverter, I would like to put something in for convenience. I am not looking to spin a saw off of it. I was thinking something along the lines of a 400w unit.

Any helpful suggestions, recommendations for sourcing supplies, or quick wiring diagrams would be appreciated.
Disclaimer: I'm not sure that this is the right section to post in, since my request for help spans several different topic areas. Mods please move it for me if I'm in the wrong place, or let me know where to repost it if necessary.

Most if not all emergency vehicles use a dual battery setup with isolator to ensure that sirens etc (off the 2nd battery) does not flatten the main cranking battery.

Google "oldspark uibi" if interested, else investigate voltage sensing isolators.

There are multiple ways to skin this cat. If you want one primary wire choose the wire that will best fit your expected total current draw based on this, or a similar chart - https://www.the12volt.com/info/recwirsz.asp

Based on the chart above, a 4awg wire can safely handle 150A of current. Based on your list above this may be enough (depends on the amp, really). I would assume, however, that if your emergency lighting is all turned on and activated you probably won't have the stereo playing full volume.

The most important thing with a setup like this is fusing. Make sure you fuse the 4awg (or whatever you choose) within 18" of the battery (closer if possible). Then, whenever you switch to a smaller wire you MUST fuse the smaller wire to the appropriate level. Proper fuse sizes should be calculated on expected loads, but should NEVER be higher then the max current the wire can handle. If you run more current through a wire then it can handle it will heat up which can lead to fire (I have seen it happen!).

As long as it is fused properly you shouldn't have issues.

You shouldn't have to run a ground back to the battery. Make sure your battery has a decent ground on it now, as well as the alternator and motor. You may want to search for the "big 3" and consider upgrading them.

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Kevin Pierson