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LUDELVR
09-11-2014, 04:55 PM
Just seeing if anyone could...shed some light for me on this topic! Bwah bwah bwah

I'm looking to hook up a light bar on my jeep with 5 lights that are 55 watts each. I was originally thinking of hooking them up using one 30 amp relay and a 30 amp inline fuse. From my calculations, I would be running at 275 watts total on this setup (excluding my other lights) divided by 12 volts to give me 22.9 amps. If this is the case, could I effectively run the 5 spot lights off of the one relay and inline fuse or should I go with 2 relays and if so, how would the wiring schematic look for that?

Any...bright ideas? :banghead:

Okay, I'm done.

sr20s14zenki
09-11-2014, 05:15 PM
You could run a dual 87 relay. On a normal relay, 87 is connected when energized, and 87a is connected when not energized. On a dual 87 out, each pole is good for 30 amps, so its essentially two in 1.

:dunno:

Crazyjoker77
09-11-2014, 06:33 PM
its perfectly fine to run just a single relay as long as it is rated for 30A. A good rule of thumb for electrical equipment is 80% of its rating for continuous use which your lights are well under.

Fuse size should be chosen based on wire size and wire size should be chosen based on the load.

For a 30A fuse 12G wire would be the minimum i would use 10 would be ideal. Going with bigger wire is actually gonna increase the brightness of the lamps a little bit as you will have more voltage at the load.

The only real advantage to having 2 relays is that you would be able run them in 2 banks and not always have to have all 5 lit.

LUDELVR
09-11-2014, 08:14 PM
Originally posted by Crazyjoker77
its perfectly fine to run just a single relay as long as it is rated for 30A. A good rule of thumb for electrical equipment is 80% of its rating for continuous use which your lights are well under.

Fuse size should be chosen based on wire size and wire size should be chosen based on the load.

For a 30A fuse 12G wire would be the minimum i would use 10 would be ideal. Going with bigger wire is actually gonna increase the brightness of the lamps a little bit as you will have more voltage at the load.

The only real advantage to having 2 relays is that you would be able run them in 2 banks and not always have to have all 5 lit.

Yeah, that's what I was thinking but then I remembered I have my fog lights powered by my park lights as well as 4 other spot lights powered off of one circuit (same 55 watt spot lights, 2 on the lower windshield hinges and 2 on the front bumper) so I figure having all of the top row would be good off of one switch.

So you reckon because it's well under 30 amps for the 5 lights, I could get away with one relay and inline fuse? :dunno:

LUDELVR
09-11-2014, 08:18 PM
Originally posted by sr20s14zenki
You could run a dual 87 relay. On a normal relay, 87 is connected when energized, and 87a is connected when not energized. On a dual 87 out, each pole is good for 30 amps, so its essentially two in 1.

:dunno:

I'm running a couple if those relays now with my other lights, 2 separate circuits but I don't recall ever messing with the center prong, think it's the 87a fuse. I always leave that open as per the instructions I find in the interwebz :dunno:

rx7_turbo2
09-11-2014, 08:23 PM
Originally posted by Crazyjoker77
The only real advantage to having 2 relays is that you would be able run them in 2 banks and not always have to have all 5 lit.

Running 2 relays and 2 fuses also means that if the relay shits the bed or a fuse blows you won't lose the entire light setup. That's how I would do it, just in case.

sr20s14zenki
09-11-2014, 08:30 PM
Originally posted by LUDELVR


I'm running a couple if those relays now with my other lights, 2 separate circuits but I don't recall ever messing with the center prong, think it's the 87a fuse. I always leave that open as per the instructions I find in the interwebz :dunno:

Thats what i said, its not a relay containing an 87 and and 87A, it has TWO 87.

something like this

http://www.12voltplanet.co.uk/user/Relay_with_twin_output.png

With a normal relay with an 87 and an 87a , when the coil is energized, 87 is on while 87a is OFF, so when the coil is not energized 87a is on and 87 is OFF

With the one im talking about, TWO 87 outputs are activated upon energizing the coil.

So, as far as load splitting, the dual 87 is good for that. They are commonly used for headlight upgrades. But as rx7 said, with two fuses and two relays, you wont lose the whole setup if a component shits the bed. I like to use them on my ECU wiring jobs (when the fuse box is not supplied). I use one to power the ecu with one of the 87 poles, and about 5 or 6 12V low draw items with the other pole (wideband, PWM idle control, boost control, etc..)

LUDELVR
09-11-2014, 08:41 PM
Originally posted by sr20s14zenki


Thats what i said, its not a relay containing an 87 and and 87A, it has TWO 87.

something like this

http://www.12voltplanet.co.uk/user/Relay_with_twin_output.png

With a normal relay with an 87 and an 87a , when the coil is energized, 87 is on while 87a is OFF, so when the coil is not energized 87a is on and 87 is OFF

With the one im talking about, TWO 87 outputs are activated upon energizing the coil.

So, as far as load splitting, the dual 87 is good for that. They are commonly used for headlight upgrades. But as rx7 said, with two fuses and two relays, you wont lose the whole setup if a component shits the bed. I like to use them on my ECU wiring jobs (when the fuse box is not supplied). I use one to power the ecu with one of the 87 poles, and about 5 or 6 12V low draw items with the other pole (wideband, PWM idle control, boost control, etc..)

Ohh ..I get it! I totally thought you were referring to the 87a relay. Didn't even know hey made a dual 87. I'll have to look into that when I go to the store. I'll also consider rx7's method too.