Advice Needed on Wiring

[cbradley]

I am about to try my hand at some automotive electrical work and I am hoping not to burn my rig down. I've drawn up a schematic showing the addition of an inverter, BlueSea fuse block and (2) 12v convenience receptacles I'd like to install as a first step, based on what I've culled from doing research on the internet (yikes). If I could get some advice/review of the diagram, I'd really appreciate it. If there is a way to do it cheaper, please let me know.

Thanks ahead of time for any help you can offer.
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[1911]

Certainly looks safe, as long as you use wire gauges appropriate for your inverter and total accessories amperage draw. One other thing you might consider (if this is your only battery and not the second battery in a dual-battery system) is to use a relay to switch auxiliary power on and off with ignition, so that you don't accidentally drain your (only) battery.

 

[cbradley]

Thanks for the comment. I'm doing the calcs on the impedance and will add the wire sizes to the diagram soon. If the battery outputs at 12.6, is any input voltage above 12.0 at the inverter acceptable?


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[Scott Brady]

Looks good Chris. I can also recommend that you run wiring for the aux. lights, a future permanent HAM install, GPS, etc. all at the same time. Running the wires is usually the biggest time suck, so doing it all at once is good timing.

 

[Utah KJ]

The diagram posted gives you a choice of breaker or ANL fuse at the Batt; 12V breakers are terrible things so the ANL fuse would be the better choice. Most of the 12V breakers I am aware of essentially are tripped by excessive heat which makes them big ole' in-line resistors. The ANL fuse will protect your vehicle and offer the least amount of voltage drop.

 

[cbradley]

Looks good Chris. I can also recommend that you run wiring for the aux. lights, a future permanent HAM install, GPS, etc. all at the same time. Running the wires is usually the biggest time suck, so doing it all at once is good timing.

Scott, thanks for the advice, that is a really good point. I'm going to update my diagram for all the future stuff and wire accordingly.




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[cbradley]

The diagram posted gives you a choice of breaker or ANL fuse at the Batt; 12V breakers are terrible things so the ANL fuse would be the better choice. Most of the 12V breakers I am aware of essentially are tripped by excessive heat which makes them big ole' in-line resistors. The ANL fuse will protect your vehicle and offer the least amount of voltage drop.

I hadn't thought of the added resistance. All the breakers i have found are the thermal type as you pointed out. I'm already worried about too much redistance since I have some long runs to the back of the vehicle. I'm looking at a Class T fuse right now.


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[cbradley]

I also decided to switch the location of the fuse and the on/off switch so I can change the fuse without unplugging the battery.


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[THATSALEXUS?]

Here are my recommendations FWTW:
• Go ahead and use a circuit breaker under the hood such as the Blue Sea with a manual trip
o This kills two birds with one stone: protection and switch
o Keep in mind the resistance of a CB is so low that the internals shouldn't get hot unless there's a problem. You won't notice it in the real world
• Up the size of the CB
o A 600 watt inverter can draw 50 amps. That plus your power ports and you don't have the current capability to add more circuits to the fuse block you paid good money for
o Think about everything you will ever run and choose your cable size and CB accordingly
• Move the fuse block inside, maybe under the seat next to the inverter
• Without knowing what else you're connecting to the fuse block, why not run a separate wire to each power port so you aren't distributing fuses all over your vehicle? Thereby complicating troubleshooting.
• If you want the inverter to only turn on with the ignition switch, most inverters' built in switches merely switch the constant power they are fed. You can substitute that input with a good accessory or ignition source and save yourself the relay. This requires opening the inverter and running a wire into it, but generally cheaper and easier than purchasing and wiring a relay capable of +/- 60 amps.

 

[cbradley]

Out of curiosity, should the CB and Ham radio go through the fuse block or is it better to run them straight to the battery to cut down on line noise?

 

[cbradley]

In reading THATSALEXUS?'s post regarding the draw from a 600W inverter, it got me looking at the manual. For some reason, the manufacturer recommends an 80A fuse/breaker.
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That said, the inverter is rated at 540W continuous and 1200 watts surge. At 12V, 540W = 45A and 1200W = 100A. At surge, the inverter would blow the 80A fuse recommended by the manufacturer. Something doesn't seem right here. Can anyone explain that to me?
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Also, in researching the sizes of wires, I noticed some discussion about factors of safety, some recommending not going over 50% of the wires rated amperage. Is this standard? Any recommendations on factor of safety? Isn't there already a factor of safety built into the recommended amperage for the wire?

 

[cbradley]

Updated the diagram.

• Revised per comments
• Added wire size
• Added wiring distance diagram

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[1911]

Out of curiosity, should the CB and Ham radio go through the fuse block or is it better to run them straight to the battery to cut down on line noise?

Noise-wise, it is better to run radio power straight to the battery, HOWEVER in my experience, modern cars/trucks are better shielded electrically than they used to be, and a good aux. fuse block installation will often run radios just fine without undo noise. If you do get RF noise you can add appropriate ferrite chokes to the power leads and antenna coax. I have the ham and cb radio power in both of my 4WD trucks run through auxiliary fuse blocks without any problems, FWIW. YMMV.

 

[THATSALEXUS?]

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Also, in researching the sizes of wires, I noticed some discussion about factors of safety, some recommending not going over 50% of the wires rated amperage. Is this standard? Any recommendations on factor of safety? Isn't there already a factor of safety built into the recommended amperage for the wire?

Your best bet in determining the correct wire gauge is to use a chart that will provide recommeded gauges for a given length and current. It's simple and as accurate as you will need for most applications. They can be found all over the web. Here's one example my techs use, just scroll down:

http://www.whelen.com/_AUTOMOTIVE/install/143/14326.pdf

 

[cbradley]

Thanks for the link.


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