Wiring 4 lights on roof rack

[gmoney35c]

Wiring 4 lights on roof rack (Hella FF 75 *pics*) GOBI

Hey Guys,

I purchased two sets of Hella FF 75 Driving Lights (55watts).

Is it safe to use single 30amp 12v relay for all 4 lights? Also, plan on tapping into high beams and using rocker switch.


Thanks

 

[Antman]

I have the same setup. No problem with 1 relay. Use a decent gauge power wire from the battery and to the lights. I think I used 10 or 12 gauge...

I use the lights just about every morning on the country roads on my way to work, no problems.

 

[Socco]

Lets do the math:

Volts (13.8) x Amps (30) = 414 Watts Capacity for a 30 A relay.

55 Watts per Light x 4 = 220 Watts that the lights draw
Ok, so we know the relay is safe to use.

Now running the primary wire for the circuit:
220 Watts/13.8 Volts = 15.9 Amps draw for 4 lights.
18 Ga wire is good to 15 Amps.
This is easily handled by 16 Ga wire as it's max current is 23 Amps.

 

[Antman]

Technically...the math says 16Ga, but allow me to add something (argue ).

The length of the power wire, and the added resistance of the connections will come into play here, along with the amount of time the lights will be used, at any given point. Let's say the relay is located under the dash, since the OP is planning on switching it with the high beam wire. You will have approx 4-5 feet of wire (plus a fuse) feeding the relays switched input. No problem there, right? The output to the lights is a different story. That wire will travel down the length of the vehicle under the sillplates, up the rear pillar and out to the roof to the Gobi. At this point it will be spliced into the Gobi wiring, which will travel an equal distance to the lights. 4 halogen 55W lights wired in parallel will cause that 16 Ga wire to get nice and warm if left "on" for awhile, I would bet on it. If LED's were being used, I would say go for it (16 Ga).


Sooooo, that's it. I am not an Engineer,nor am I an expert on the subject, but I have tons of real-world experience- been wiring circuits on vehicles since the late '80's, and I have made my fair share of mistakes in the past. Maybe it'll be fine, but it wouldn't go on my vehicle that way! :hatsoff:

PS- HAPPY NEW YEARS FELLA's!!

 

[CanElec]

New guy here. I would use Antman's suggested sizing. A minimum of #12 should be used, I wouldn't carry a load on anything less than #14.

 

[Socco]

I'm always up for an argument :boxer:

Now I never insinuated that using a larger gauge is wrong (Although using 12 or 10 in this case is just a waste of money). I wanted the OP to know why it could work, beyond "This guy did it so..." Now, although the math says it's fine, common industry practice is to upsize by one for your fudge factor. Thus 16 becomes 14 ga.

Now why would you waste 12ga on a circuit that might need 18ga? With that approach you could wire everything in 8/2 Teck and feel even safer yet.

I too am neither an engineer nor an expert. However, I did work in the aftermarket 12V industry for 4 years following 8 years in a Heavy Duty repair shop.

Now lets hug it out :bigok:

 

[Antman]

Now lets hug it out :bigok:

Ha! Gimme a hug big guy! I am from the old school where you over build it and it lasts forever.:shrug:

Since you have real world experience as well, what do you think about the length of the wire? That was my main reason for wanting the larger Ga.

 

[Jtraskell]

Ha! Gimme a hug big guy!

So much love on this forum........goose bumps all over.

 

[CanElec]

there are many factors to look at when selecting wire size, are they run in free air or are many wires bundled together,the temp rating on the insulation of the conductors, length of conductors etc. The Canadian elect. code states that #14 guage with an isulation temp rating of 60-90 degrees C is good for 15 amp, #12 is 20 amp and 10 is 30 amp. National elect code states #14 with a temp rating of 60 is good for 16 amp and with a temp rating of 90 degrees is good for 21 amp, #12 is 20 and 27, #10 is 27 and 36. Wires should only be loaded to 80% of thier max capacity and be fused at what is stated in the code,when doing the math the battery voltage should be used (12v) which would bring the load to 18.3amps. I hope this helps I am new to forums and am trying not to ramble.

 

[Okki]

I have an entire write up here

I've included the diagram below to add some more detail to the hug-fest

AUXILARY FUSE BOX & LIGHTS
Fasterners $5.19 Nuts and bolts Ace Hardware
Butt Connector 16-14A $1.06 Electrical connector Ace Hardware
Heat shrink Tube $13.89 3/16 and 1/4 tubes Advance Auto Part
Add-a-circuit $7.48 O'Reilly auto Parts
15amp mini fuse $4.59 O'Reilly auto Parts
Plastic Weld $5.87 JB Weld O'Reilly auto Parts
1 reel CTI 85732 $6.41 Wire used in harness O'Reilly auto Parts
1 x SS 01402 $3.52 Copper Lug O'Reilly auto Parts
4 x BWD BH161 $2.53 Copper Lugs O'Reilly auto Parts
6Ft BWD PW8R $5.07 Wire between battery and fuse box O'Reilly auto Parts
40Ft BWD PW12R $16.69 Wire from fusebox to lights O'Reilly auto Parts
Blue Seas ST Blade Fuse Block with Cover $27.95 OTRATTW
Three Position V-Series Switch Holder $5.30 OTRATTW
VMS-01 $1.75 Single Switch Holder OTRATTW
V1D1J66B-AYC9A-CP1 $12.30 Compressor Rocker , Blue OTRATTW
V1D1J66B-AFC77-18B $12.30 Back up Lights, Amber OTRATTW
V1D1J66B-AFCN5-17U $12.30 Driving Lights, Amber OTRATTW
V1D1J66B-AFCM4-RF1 $12.30 Roof Lights, Amber OTRATTW
VPS-CAR $1.00 V-Series gasget seal OTRATTW
Stinger 80 Amp Battery Relay Isolator $23.79 Amazon
2 x HELLA 007133831 Micro FF Series $108.78 12V/55W Halogen Driving Lamp Kit Amazon
Total $290.07

And a parts list for good measure!

Okki

 

[Antman]

Wow.

 

[Okki]

Wow.

Come On Antman.. you dont have a spreadsheet keeping track of all parts costs and statistics associate with your truck? LMAO :banana: :nerd:

Okki

 

[gmoney35c]

Thanks EVERYONE for all the suggestions and expertise! Successful install/wiring with all of above input. I added pics to top OP.

 

[phillyd2]

I also have 4 x 55w lights on top of my Gobi but honestly they don't offer much more light that the High Beams. What are you seeing?

 

[gmoney35c]

will have to get back to you as I have not been able to test on road. Will update later with performance and pics.