Grounding to frame or battery for fridge and compressor in bed.

[Jems007]

If I want to run my viair 450 I’ll need be able to handle 23 amps which means I’ll need to run 8 gauge if I ground to nearby frame—but if I run back to battery I’ll need to Use 6 awg or possibly 4 awg for the round trip to account for V drop.

does this work? Do you recommend frame ground back near the bed or go larger wire and round trip it?

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[j.o.y.ride]

If I want to run my viair 450 I’ll need be able to handle 23 amps which means I’ll need to run 8 gauge if I ground to nearby frame—but if I run back to battery I’ll need to Use 6 awg or possibly 4 awg for the round trip to account for V drop.

does this work? Do you recommend frame ground back near the bed or go larger wire and round trip it?

23 amps needing 6 or 4 gauge? No way. Not unless you're trimming your truck with it as a decoration and it's like 50 feet long.

 

[Jems007]

23 amps needing 6 or 4 gauge? No way. Not unless you're trimming your truck with it as a decoration and it's like 50 feet long.

from battery to outlet near bed of truck I am guesstimating could be 12-15’, so a round trip of 24-30’ at 25 amps. Anything over 20’ calls for 6 AWG at 25 amps. This would be if I went round trip from battery to plug and back to battery.

 

[j.o.y.ride]

from battery to outlet near bed of truck I am guesstimating could be 12-15’, so a round trip of 24-30’ at 25 amps. Anything over 20’ calls for 6 AWG at 25 amps. This would be if I went round trip from battery to plug and back to battery.

You don't count the round trip, you count the length of the individual wire to accessory. 12-15 feet for positive and 12-15 feet for negative. Running 6 or 4 gauge for a 23A pump is insanity.

Also, why ground all the way back to the battery anyhow? Totally unnecessary.

 

[Jems007]

You don't count the round trip, you count the length of the individual wire to accessory. 12-15 feet for positive and 12-15 feet for negative. Running 6 or 4 gauge for a 23A pump is insanity.

Also, why ground all the way back to the battery anyhow? Totally unnecessary.

I thought you had to calculate the length of all wire runs including the ground. Am I wrong on that?

Some say a direct to battery ground is preferred as a stronger ground, and less chance of issues with corrosion, interference with other tech on the Jeep (I.e. radio, comms)

 

[ShadowsPapa]

Right. Do not count total length of + and -
Count only the distance from + to the unit as one length and account for that and if you decide to run a wire for the ground back to the front, do the same for that. Figure each independently.
I'd ground to the frame or chassis - look at what Jeep grounds to the body - look at all of the ground points in the engine bay. The ground for your trailer wiring doesn't go clear back up to the battery and that takes some hefty amperage.

 

[ShadowsPapa]

I thought you had to calculate the length of all wire runs including the ground. Am I wrong on that?

Some say a direct to battery ground is preferred as a stronger ground, and less chance of issues with corrosion, interference with other tech on the Jeep (I.e. radio, comms)

No chance of interference. Look at what Jeep grounds to the body. No issues.
And no, do not total the wire runs for a total distance.
If the wire feeding the unit in the rear is 16' long, calculate only for THAT 16' and nothing else.
Again, Jeep doesn't home-run every ground point. That's impossible. Ground to the chassis. Those stating it will interfere with things aren't electricians.
A chassis ground is actually less likely to interfere than a dedicated wire running the length of the truck.
Pick a spot that's clean, perhaps that Jeep is already using as a ground point. You can seal it with liquid tape or some other product. Pick a ground point that's not likely to get wet.

 

[Jems007]

No chance of interference. Look at what Jeep grounds to the body. No issues.
And no, do not total the wire runs for a total distance.
If the wire feeding the unit in the rear is 16' long, calculate only for THAT 16' and nothing else.
Again, Jeep doesn't home-run every ground point. That's impossible. Ground to the chassis. Those stating it will interfere with things aren't electricians.
A chassis ground is actually less likely to interfere than a dedicated wire running the length of the truck.
Pick a spot that's clean, perhaps that Jeep is already using as a ground point. You can seal it with liquid tape or some other product. Pick a ground point that's not likely to get wet.

Thanks for the help. There are two ground bolts behind the spare tire- I’ll use those. Looks like I’ll be able to use 8 awg. I already ran 10 awg so I have some backtracking to do.

 

[j.o.y.ride]

Thanks for the help. There are two ground bolts behind the spare tire- I’ll use those. Looks like I’ll be able to use 8 awg. I already ran 10 awg so I have some backtracking to do.

10GA is totally fine. This is a short term use item. Maybe 5-10 minutes. You won't draw so many amps as to melt 10ga vs 8ga.

 

[Jems007]

10GA is totally fine. This is a short term use item. Maybe 5-10 minutes. You won't draw so many amps as to melt 10ga vs 8ga.

That’s good to know! The max amp draw the viair lists is 23 amps. So you’re thinking I’m good keeping the 10 awg for that span of 15’ or so?

 

[j.o.y.ride]

That’s good to know! The max amp draw the viair lists is 23 amps. So you’re thinking I’m good keeping the 10 awg for that span of 15’ or so?

You will be fine. It would be best to go to 8ga but 15 feet 23a is right on the border of 10 and 8. If this was an audio amp that would be running for long periods then def 8. But it isn't.

 

[Beemer533]

I think I would stick with 8awg. Running for a "long time" is kind of relative.

Are you using it to air up your tires? How big are the tires? Going from 15 psi up to 30 In a 35 can take some time.

Running airtools? On top of anything you do with the compressor the fridge most likely always be running.

I'd go with 8awg for the relatively minor price difference and peace of mind.

 

[Radio Guy]

Speaking as a former installer of car stereos, commercial two way radios, etc, I say use 6ga for the positive and ground to the vehicle chassis. If this were a high power two way radio or car stereo amp I would then run both the hot and ground to the battery to avoid noise and interference but in this case your compressor doesn't care.

Using 10ga wire will give you about .85 Volt drop in a 15ft run and going to 6ga will be about .34 Volt drop. That can make a slight difference in the time it takes to air up the tires. It doesn't hurt to upsize the wire and you might upgrade the compressor some day to a larger one.

When powering an item that is floating from the vehicle chassis for grounding you have to take both the + and - conductor into account for voltage drop. If you had a 15ft run to the battery you have voltage drop through 30ft of wire. Its impossible to estimate the voltage drop through the chassis but its not a show stopper at 23A.

 

[Jems007]

I think I would stick with 8awg. Running for a "long time" is kind of relative.

Are you using it to air up your tires? How big are the tires? Going from 15 psi up to 30 In a 35 can take some time.

Running airtools? On top of anything you do with the compressor the fridge most likely always be running.

I'd go with 8awg for the relatively minor price difference and peace of mind.

I'll be going from 15psi up to 36 on 38" tires. So it could be a 20 minute affair. The question is...possibly not at full draw though since this thing is rated at Max draw of 23 Amps. Its a 100% duty cycle at 100 PSI.

 

[Jems007]

When powering an item that is floating from the vehicle chassis for grounding you have to take both the + and - conductor into account for voltage drop. If you had a 15ft run to the battery you have voltage drop through 30ft of wire. Its impossible to estimate the voltage drop through the chassis but its not a show stopper at 23A.

So this is what I was asking earlier. If I were to run all the way back to the battery I'd need to double the length, which would mean 6 AWG would be the way to go. If I ran a ground to nearby frame that was 2' instead of 15' I'd need to calc 17' voltage drop.

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