Wire Size Assistance Requested

WVI

Adventurer
Good Day.
I am replacing the defunct cigarette light receptacle on the dash of the van.
The largest item that may be plugged into it is a small portable fridg/freezer as well as charging a cell or running GPS.
I will be using a switched relay and the relay will be under the hood by the battery.

I'm seeking suggestions on wire size to run to the receptacle.

Thanks for your time.
 

WVI

Adventurer
Thanks for the link SquirrelZ.
The freezer will be here tomorrow so I can get the specs.
 

WVI

Adventurer
Thanks for mentioning that Dreadlocks. I wouldn't have and I may just use common body/frame ground.
 

LandCruiserPhil

Expedition Leader
Good Day.
I am replacing the defunct cigarette light receptacle on the dash of the van.
The largest item that may be plugged into it is a small portable fridg/freezer as well as charging a cell or running GPS.
I will be using a switched relay and the relay will be under the hood by the battery.

I'm seeking suggestions on wire size to run to the receptacle.

Thanks for your time.
Simple answer minimum #10
Size fuse based on outlet capacity
No need for a relay if used for a fridge
 

DRP

Member
Thanks for mentioning that Dreadlocks. I wouldn't have and I may just use common body/frame ground.
Frame is fine but you still need to figure both directions when you plug your numbers into the circuit wizzard
 
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dreadlocks

Well-known member
yeah the BlueSea calculator wants total length of conductor, so figure the run 2x for DC.. other calculators may specify for 2 wire conductor and do that for you.. pay attention to that.. if you start using chassis ground for anything considerable its not a bad idea to upgrade/add to your grounding points for engine/battery to cope for the additional loads.

for larger loads I'd suggest calculating max amps take the wattage / 10v just to be on the safe side.. a 800W load @ 14.2 is 56A, 12v is 66.6A, at 10v its pulling 80A.. If you had a battery fault or something happen that drains your battery flat it could start burning up cables/connectors if you didnt account for it.
 
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Robert Bills

Explorer
What is a "legitimate" Expo Guy?

If two Expo Guys disagree, does that make one of them illegitimate? ;)


BTW - I typically fuse based on wire size (aka conductor capacity)because I was taught by an auto electrician who never even dreamed of leaving the city limits that the proper way to do things is to fuse to protect the wire except when there is a reason to reduce the fuse rating to protect an expensive appliance such as a ham radio, etc. My only point is that sometimes legitimate Expo Guys fuse to protect the conductor, which is the typical way of doing things, and sometimes those same legitimate Expo Guys fuse to protect the appliance - it depends upon the particular situation.


Oh yeah, the original question was about wire size. I would use 12 gauge maximum in OP's application for a dash mount power port. Depending upon the power consumption of the fridge, 14 gauge might even be sufficient. In my mind, running 10 gauge in this particular situation is like owning a Prius and knowing you will never drive anything larger than a Prius but commissioning a tunnel to get to your house large enough for a locomotive. Can't hurt, but it won't work any better as a tunnel for a Prius. Also, depending upon the power draw of the fridge, a relay may not be necessary.
 
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LandCruiserPhil

Expedition Leader
That seems odd. A legitimate ’ExPo Guy will size their fuse based on conductor capacity or if lower and desires to, the expected appliance load.
I assume you are referring to me just not sure on the legitimate part.
To clarify my post to be fused at the outlet capacity, not the conductor capacity. So yes for the loads the OP stated and wiring "a" 15A rated dash outlet as most are I would fuse at a max. 15A when using #10.
 

LandCruiserPhil

Expedition Leader
<snip>


Oh yeah, the original question was about wire size. I would use 12 gauge maximum in OP's application for a dash mount power port. Depending upon the power consumption of the fridge, 14 gauge might even be sufficient. In my mind, running 10 gauge in this particular situation is like owning a Prius and knowing you will never drive anything larger than a Prius but commissioning a tunnel to get to your house large enough for a locomotive. Can't hurt, but it won't work any better as a tunnel. Also, depending upon the power draw of the fridge, a relay may not be necessary.
If #10 is overkill for a fridge why do the fridge manufacturers use #10 if you buy a factory add an outlet? To run any smaller wire safely I would fuse it lower. Point being when most others see an outlet it has unlimited power available so you need to protect it properly.

Curious when would a relay ever be needed for a fridge?
 

dreadlocks

Well-known member
if its got an internal LVD it needs a pretty heavy gauge or it wont have a very good idea at battery voltage under load.. the idea is to have basically no voltage drop when you have a remote LVD or else your fridge cuts out early.

2% voltage drop @ 12v is 0.24v, there's a pretty big capacity difference between 12v and 12.24v, like 20% SOC.
 

Robert Bills

Explorer
If #10 is overkill for a fridge why do the fridge manufacturers use #10 if you buy a factory add an outlet? To run any smaller wire safely I would fuse it lower. Point being when most others see an outlet it has unlimited power available so you need to protect it properly.

Curious when would a relay ever be needed for a fridge?
12v underground landscape wire is also commonly 10 gauge, but sometimes 12 gauge. I've used the 10 gauge version for compressor wiring in some vehicles because it is cheap, flexible, with + and - wires bundled together for my installation convenience. If I had a long wire run then 10 gauge would begin to make sense in this application, but OP's run is short - from the battery to behind the dash - so I wouldn't be concerned about voltage drop. I think 12 gauge primary wire is plenty, and is easier to work with.


I agree with you that it is difficult to imagine a situation where a 12v portable fridge would require a relay. But its possible. That's why I hedged my bet by saying "depending upon power draw."

I also agree that a lower amperage fuse than the wire is rated to carry will prevent people from overloading the circuit with add-ons, and since most power port plugs are rated at 15 amps that is the weak link in the circuit mandating no greater than a 15 amp fuse regardless of the wire size used.
 
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WVI

Adventurer
DRP & Dreadlocks, I figured on doing the partial run length if I ground to chassis.

Robert Bills, I had always been under the impression that the fusing would be for the wires...I remember my old 72 International and how all it's dash wiring melted in an instant one night driving home in washington. Thanks for the tip on the landscape wire. I can see that handy for some things..

I've had the outlet for some time. I glanced at it today, and I seem to recall it is a 30A receptacle.

Later down the road I'll wire the back of the van. For now, I plan on putting the fridge between the front seats and building a vented box for it....That way we have room for our pup to sit and look out the window while driving.

I really do appreciate all the advice. Thanks Folks.

Oh, the reason I'm running it off a relay is so I can shut both outlets off when not in use. For some reason I am thinking the fridge would pull amps like an old set of fog lights. I guess the routing on this could do without now that I think about it.
 
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