I think i finally figured out how to wire up my whelen bar, I have kind of a stupid question, i'm going to use 4 50 amp relays. 1 for each circuit. What exactly do relays do? do they take the amps coming in and convert it to less amps, or does the relay take in the large amount of power and only supply a small amount to the bar? I don't know if this is really a great explanation but i'm wondering. It seems that each circuit i have is roughly 40 amps so i'm going to use 50 amp breakers so it don't peak and kick the relay but i'm going to use like 12 and 14 gauge wire and everyones saying with relays its plenty, i'm just trying to understand how. Thanks for the response.
relay question
- Thread starter thejudges69
- Start date
What Kind of Whelen bar are you installing? in the simplest form a relay is a switch it utilizes low current inputs to control high a high current out put. In terms of providing power to the light bar either fuse it properly to the battery, or use a circuit breaker
usdemt
Member
I would back up here a lot. First of all your breakers or fuse size depends on what amperage your pulling and at what distance not the size of your relay. Figure out how much each pulls, 50 amps is way more than enough for an entire 42 inch lightbar. What kind of bar is it? Relays also do not "create power" they simply provide a way to switch a higher amperage load with a small amperage trigger wire. You use them if the switch you are using is rated at 5 amps but you need to switch 20 amps. Here is some good info on relays.
I am not exactly sure what you are referring to when you say each circuit. But check into how much each "circuit" is pulling because there is not a lightbar out there that will pull a total of 160amps, much less an alternator that can handle it, haha.
Check here to on your wire size because if you indeed are running a 50 amp breaker 14 guage wire can only safely handle if the wire is shorter than 4ft and 12 guage can only handle 50 amps at 6 ft. Wire Guage Chart
My suggestion, get a case of beer and a buddy who is knowledgeable in 12v electronics to start showing you the basics.
I am not exactly sure what you are referring to when you say each circuit. But check into how much each "circuit" is pulling because there is not a lightbar out there that will pull a total of 160amps, much less an alternator that can handle it, haha.
Check here to on your wire size because if you indeed are running a 50 amp breaker 14 guage wire can only safely handle if the wire is shorter than 4ft and 12 guage can only handle 50 amps at 6 ft. Wire Guage Chart
My suggestion, get a case of beer and a buddy who is knowledgeable in 12v electronics to start showing you the basics.
I have a whelen edge 9000 bar, Its a 60 inch bar that i had custom built by a guy. It has a total of 4 circuits in it, here is the lay out.
circuit 1: 6 linear tubes
circuit 2: 6 helix tubes wired for rapid flash
circuit 3: 4 halogen flashers
circuit 4: 4 more halogen flashers.
I can't seem to figure out the power draw on this bar. the way i was going to wire it was a 4 gauge wire into a heavy fuse holder from the battery with a dual 80 amp fuse holder, then out of each 80 amp circuit with wiring to 4 50 amp relays, 1 relay for each circuit, meaning 1 relay for the linears, 1 relay for the helix, and 1 relay for each halogen circuit. then the wiring out to the bar would be 12 gauge. Just so its understood, the bar is roughly 25 feet from the switch and relays to the bar, its mounted on the top of my headache rack on the back of my peterbilt. Some people are saying i don't need relays that big, but i can't seem to find out what the power draw is on any of the bulbs in the bar. I think i'm making a good move towards figuring this out but just want it to be right. Hope that i explained this good enough.
Anyways i'm trying to figure out the power draw and am i on the right track for the wiring? i have pics of the bar but none of the relays or fuse holder, that stuff is at home and i'm not right now. any suggestions of something to make it better?
circuit 1: 6 linear tubes
circuit 2: 6 helix tubes wired for rapid flash
circuit 3: 4 halogen flashers
circuit 4: 4 more halogen flashers.
I can't seem to figure out the power draw on this bar. the way i was going to wire it was a 4 gauge wire into a heavy fuse holder from the battery with a dual 80 amp fuse holder, then out of each 80 amp circuit with wiring to 4 50 amp relays, 1 relay for each circuit, meaning 1 relay for the linears, 1 relay for the helix, and 1 relay for each halogen circuit. then the wiring out to the bar would be 12 gauge. Just so its understood, the bar is roughly 25 feet from the switch and relays to the bar, its mounted on the top of my headache rack on the back of my peterbilt. Some people are saying i don't need relays that big, but i can't seem to find out what the power draw is on any of the bulbs in the bar. I think i'm making a good move towards figuring this out but just want it to be right. Hope that i explained this good enough.
Anyways i'm trying to figure out the power draw and am i on the right track for the wiring? i have pics of the bar but none of the relays or fuse holder, that stuff is at home and i'm not right now. any suggestions of something to make it better?
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The key here is that AMPS = WATTS / VOLTS.
For instance, a 35 watt lamp that operates on 12 volts draws just shy of 3 amps. A setup of four 35-watt halogen lamps, flashing two-by-two, draws just shy of 6 amps. However, a setup of four 35-watt halogen lamps, all flashing simultaneously, draws just shy of 12 amps. This leads me to believe that, presuming your halogen flashers operate strictly in an alternating pattern, you could safely fuse circuits 3 and 4 each with a 10 amp fuse, or maybe even each with a 7.5 amp fuse.
A Whelen EB6 has a fuse holder in its main power lead that comes with a 15 amp fuse installed at the factory. This is a common power supply used in the Whelen Edge. Other power supplies found in the Whelen Edge are similar to the EB6 in their draw. It would appear that circuits 1 and 2 should each draw less than 15 amps. This leads me to believe that you could fuse circuits 1 and 2 each with a 15 amp fuse.
In short, I find it hard to believe that your whole Whelen Edge would draw even 50 amps with all four circuits operating. In the field, however, I would check each circuit with a Digital Multimeter before proceeding.
For instance, a 35 watt lamp that operates on 12 volts draws just shy of 3 amps. A setup of four 35-watt halogen lamps, flashing two-by-two, draws just shy of 6 amps. However, a setup of four 35-watt halogen lamps, all flashing simultaneously, draws just shy of 12 amps. This leads me to believe that, presuming your halogen flashers operate strictly in an alternating pattern, you could safely fuse circuits 3 and 4 each with a 10 amp fuse, or maybe even each with a 7.5 amp fuse.
A Whelen EB6 has a fuse holder in its main power lead that comes with a 15 amp fuse installed at the factory. This is a common power supply used in the Whelen Edge. Other power supplies found in the Whelen Edge are similar to the EB6 in their draw. It would appear that circuits 1 and 2 should each draw less than 15 amps. This leads me to believe that you could fuse circuits 1 and 2 each with a 15 amp fuse.
In short, I find it hard to believe that your whole Whelen Edge would draw even 50 amps with all four circuits operating. In the field, however, I would check each circuit with a Digital Multimeter before proceeding.
Would it be safe to assume that I could cut this back to a 30 and 40 amp relay? 30 amp for the circuits 3 and 4 and 40 amp for circuits 1 and 2? Also is the 4 gauge wire feeding the fuse holder to much? I originally wanted to use an 8 gauge wire to power the dual circuit fuse holder. Right the moment I'm setup for 2 80 amp fuses and 4 relays so I'm going to be able to cut this all way back right?
vonirkinshtine
Member
CONSULT THE BOOK OF ARMAMENTS!
Seriously, it sounds to me like you're just throwing a bunch of fuses and relays at something without really knowing what it needs. All you need to do is add up the current draw of each of the components you want to put on a certain circuit. The sum of those components is what you should fuse at and what your relay (for that circuit) needs to be rated for. I have not messed with light bars, or light bar components, but I would assume that the amperage draw would be a piece of information readily accessible. Do a little bit of research and math and it will take away all this guess work you're stuck in.
Like the example Shues gave...say each hallogen light on circuit 3 is 35W, that's...oh hell, just call it 3 amps (I'm a fan of rounding, lol). You have 4 of those lamps in the circuit, so 4 x 3A = 12A. Now, unlike Shues, I'm not sure why you would fuse lower than your net draw. If it were me, in this example I would fuse at 12A, but use a 15A relay.
*edit* Shues was talking about alternating flashes. Which would mean that out of the 4 lights, only 2 would be on at a time which would make your instantaneous current draw 6A
Seriously, it sounds to me like you're just throwing a bunch of fuses and relays at something without really knowing what it needs. All you need to do is add up the current draw of each of the components you want to put on a certain circuit. The sum of those components is what you should fuse at and what your relay (for that circuit) needs to be rated for. I have not messed with light bars, or light bar components, but I would assume that the amperage draw would be a piece of information readily accessible. Do a little bit of research and math and it will take away all this guess work you're stuck in.
Like the example Shues gave...say each hallogen light on circuit 3 is 35W, that's...oh hell, just call it 3 amps (I'm a fan of rounding, lol). You have 4 of those lamps in the circuit, so 4 x 3A = 12A. Now, unlike Shues, I'm not sure why you would fuse lower than your net draw. If it were me, in this example I would fuse at 12A, but use a 15A relay.
*edit* Shues was talking about alternating flashes. Which would mean that out of the 4 lights, only 2 would be on at a time which would make your instantaneous current draw 6A
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usdemt
Member
Dont worry about the amperage reading on the relays unless you are over it. They are rated at up to a certain amount, in your case it sounds like 40 amps. But you can switch half an amp with a 40 amp relay just as easy. The reading is just the max that the relay will handle. 30 and 40 amp relays are common and like I said you dont need to switch 30 amps on a 30 amp circuit, follow me?
I think i'm getting this, would an 8 gauge main power be sufficient into a wiring distribution box?
usdemt
Member
Dude you have to go here http://www.ledguy.net/wire-gauge.htm to figure out wire sizes. Without knowing amperage draw and wire length we have no way of helping you just guess.
usdemt said:
The amperage draw is listed in prior posts, Shues did a breakdown on the amps used read prior posts.
usdemt said:
+1
It sounds to me like your grand total draw will be at or just below 50 amps. Double check this using an ammeter, or the ammeter function of a digital multimeter. These are easy to use, they're inexpensive, they come with instructions, and there are a plethora of tutorials and related reading materials available online.
The gauge of wire needed will vary, depending on the length of wire you will need to run from your battery to your switchbox. usdemt provided a useful link to help determine the gauge of wire needed. If you'll use 15 feet or less of wire, then an 8 AWG wire will be sufficient. If your run happens to be longer, then a larger gauge of wire is needed.
Ltrescue76_809
Member
Just throwing this out there but, does your lightbar not have a built in matrix board for with relays?....most of the whelen bars I have worked on have them...just run a main power and ground then low amp switch wires.
Ltrescue76_809 said:
No mine don't we was goin to rewire it but being its location it would be difficult to do, I was told this is basically the same just the relays are in the cab. If I would have known before hand we would have done that.