amperage,voltage,and wattage

[monstaru]

ok,so i am finally to a point to do some wiring on the brat.i am adding a secondary fuse block for my acc.'s.what i have encountered is that these fuse blocks usually have an amperage rating per circuit and an overall amperage rating.where or what is the conversion between wattage(lights & stereo) and amperage?i obviously run about 13.5 to 15.6 for my voltage depending on rpm's.does my voltage affect the amperage the block can take?is there a bigger block in my future than i am looking at?

i am looking at about 4 lights(2-55and 2-100 watt)a very low key stereo,c.b. and other add ons later.i only want a 6 gang fuse block.but what do i need to get,or am i making this way to complicated?cheers, brian

[nipper]

ok,so i am finally to a point to do some wiring on the brat.i am adding a secondary fuse block for my acc.'s.what i have encountered is that these fuse blocks usually have an amperage rating per circuit and an overall amperage rating.where or what is the conversion between wattage(lights & stereo) and amperage?i obviously run about 13.5 to 15.6 for my voltage depending on rpm's.does my voltage affect the amperage the block can take?is there a bigger block in my future than i am looking at?

i am looking at about 4 lights(2-55and 2-100 watt)a very low key stereo,c.b. and other add ons later.i only want a 6 gang fuse block.but what do i need to get,or am i making this way to complicated?cheers, brian

 

volts times amps = watts.

You are making this overly complicated. Use the max voltage something is rated for, or when in doubt 14 volts (a3.5 if you want to be anal). There is a voltage drop in the wires, one of the reasons you can use 14 instead of 15 volts.

 

nipper

[daeron]

okay.. this was best explained to me with an analogy.

 

instead of a wire, and electricity, picture a pipe, and water or air.

 

the wattage is how much work gets done by that "air" (turning your impact driver, say..)

 

the amperage could be likened to the speed at which the "air" moves inside the pipe.. one amp = one coulomb per second, or minute i forget which. a coulomb is a specific quantity of electrical charge. this is basically like saying "cubic feet per minute" of airflow... with electricity more speed (higher amps) means more heat buildup due to resistance, so your circuit is always limited... to a given rating.

 

the voltage is most like the pressure at which your system operates..

 

but a device that runs at 12 volts, and is rated at say, 300 watts is going to draw 25 amps....

 

so add up the wattage of your lights, and divide it by twelve. if you want to pad that number, you can, but you should be able to just presume 12 volts for designing the fuse layout on your lights... so you have one 110 watt circuit, and one 200 watt. a ten amp would be ample for the 110, and a 20 for the 200. The CB and stereo could probably go on the same circuit. the fuse is there to protect them from drawing more power than they are supposed to see.. without the fuse, if your stereo shorts out it will take all the juice it wants to... but with a fuse inline, if it draws more than X amps (usually 10 for stereo alone) then the fuse blows and your equipment is protected. what i am saying is, put your cb and stereo on the same circuit. (unless its some big honking CB that ive never seen the like of) if a 10 amp fuse blows, step up slowly until you dont blow them with both devices functioning normally.. (ie CB on, lit up, stereo on, pop the CD out or play it and make sure nothing blows) If you can find power ratings on the stereo and CB, then dont exceed to sum of the two.. but 15 should cover them, 20 almost definitely.

 

you might consider running each light bulb on its own fuse. thats the best way to set them up, by far. but keep in mind *while building, not repairing* that the fuse is there to protect, and if your hardwires can take it (ie your fuse panel has a high enough max rating) and you know your component is good (brand new fan that has been thoroughly tested etc etc) then the "right" fuse is the smallest one that doesnt blow under load.

 

i hope i managed to clear some confusion for you, if not please PM me. Sometimes these issues can be learned just from reading something like what i *tried* to write, but sometimes it makes a MAJOR difference actually talking to someone about it. so if you need to clear anything up go ahead and ask.

[NorthWet]

First off, stereo "wattage" is a figure that means almost whatever you want it to mean. What you need to do is find what the rated draw of the stereo is. Hopefully, somewhere in the spec-sheet for it it will list max/min operating voltage, and max amperage draw.

 

As previously stated, wattage is just the product of voltage and amperage. The trouble with dealing with non-DC power figures (stereo) is that power is time-relative: Some power ratings are given as instantaneous (peak), some are integrated (area under the time-domain curve) or RMS, and some are just fanatasy.

[Phizinza]

Heres an example of the stupidity of "ratings"

 

My 130watt spotties use about 90watts...

A cd player with 4x52watts out (thats the watts they write on the box) normally puts out about 12 to 14watts per channel at full volume. And barely uses a thing to spin the cd.

My Pioneer 800watt peak, 400watt RMS Subwoofer distorts before you can even get 170watts out a good amp into it. (note here that most people think RMS is the amount of power at which it won't distort)

A 200watt RMS Fusion brand amp can supply more wattage then a 400watt RMS Alpine amp.

 

All of that is probably pretty useless to you. But I just thought I'd say it any how.

I'd still pretend that the rated watts are real, and make the system good enough for those ridiculus amounts. It is always good to over engineer in my opinion

 

And then you have that whole peak/RMS thing with sound systems... Like how do you get a 800watt peak 400watt RMS sub when RMS just means "Route Means Squared" which is peak x by .71 or there abouts.... Craziness!

[nipper]

Heres an example of the stupidity of "ratings"

 

My 130watt spotties use about 90watts...

A cd player with 4x52watts out (thats the watts they write on the box) normally puts out about 12 to 14watts per channel at full volume. And barely uses a thing to spin the cd.

My Pioneer 800watt peak, 400watt RMS Subwoofer distorts before you can even get 170watts out a good amp into it. (note here that most people think RMS is the amount of power at which it won't distort)

A 200watt RMS Fusion brand amp can supply more wattage then a 400watt RMS Alpine amp.

 

All of that is probably pretty useless to you. But I just thought I'd say it any how.

I'd still pretend that the rated watts are real, and make the system good enough for those ridiculus amounts. It is always good to over engineer in my opinion

 

And then you have that whole peak/RMS thing with sound systems... Like how do you get a 800watt peak 400watt RMS sub when RMS just means "Route Means Squared" which is peak x by .71 or there abouts.... Craziness!

 

For lighting and other devices there is a saftey factor built in to it.

Audio wattage is crazy and there is no real basisi in fact or science for those numbers. Just go by what the mfg says it should be.

 

nipper

[monstaru]

cheers guys,i am going to pick up a fuse block that says 30 per circuit max.but it does not have an overall rating of what the block itself will take.i would think that it would be 180,but i found one that says it can handle 25 amps per circuit and only take a max of 125.what the hell does that mean?thanks again,brian

[monstaru]

bump

[nipper]

cheers guys,i am going to pick up a fuse block that says 30 per circuit max.but it does not have an overall rating of what the block itself will take.i would think that it would be 180,but i found one that says it can handle 25 amps per circuit and only take a max of 125.what the hell does that mean?thanks again,brian

 

that means how much curretn the block can handle before it melts down.

You are over thinking everything. Did you know that your light switches are rated 230 volts in your house? doesnt mean your running 230 volts.

Now that said, make sure you use proper wiring, and use the proper amperage fuses.

 

http://science.howstuffworks.com/question501.htm

 

http://auto.howstuffworks.com/wfc.htm

 

nipper

[monstaru]

i understand that is what it means.what i am doing to myself in my brain is by far more involved than it needs to be obviously.and my house is on a 100 amp service.(it's old)what i am trying to figure out is how to take the info already given to me and apply to my certain situation.i work alot, i spend time with my family alot and am generally stressed out..i can read.it does not mean it computes.i am a hands on kind of guy.the overall rating of the block is what i am talking about.to me it makes sense that a block that has 6 circuits,at 30 amp max per circuit should be able to handle 180 amps.but,the research i have been doing states to me that some blocks may have 6 circuits at 30 amp max and only handle 160 amps total.what i am asking is why it is that way.i am not asking for someone to come over and wire my car for me,i am not an FNG.i would like to KNOW what is going on before i start to ************ around with my electrical and modifying it like everything else i have.limits bro,limits.i like to break them,but i do not like fire.

[Moodybluesr]

All four of those lights together will come in at less than 30 amps, so you're good there, especially if you split them into pairs for fusing purposes.

 

(55+55+100+100) / 13.8 = ~22.5 amps drawn with all four lights on.

 

My HR2510 (10 meter rig I used for CB) was fused at 7.5amps and I had it swinging about 45 watts on a Bird meter; If you aren't going to be running any juice behind it, you are fine on the CB end.

 

The stereo will be fine as well, assuming you are just running a deck. If you plan on running an amp, you've run into a whole new monster, but again, you should be fine as long as you don't go overboard. Are you planning on running subs? Are the main drivers going to be pushed by an amp or just the deck? What amp(s) is/are you planning to run? There is a HUGE difference in rated wattage in various amplifiers, even within a brand. EX: I have an old Rockford Fosgate 500m (rated at 500 watts rms into a four ohm load) that will embarrass newer Rockford amps rated at 1000 watts rms... and will absolutely decimate cheap brand (Pyramid, Boss, etc.) supposedly rated at 2000 and 3000 watts.

 

That said, be sure you have a good, strong source for the block; I'd say at least 4 gauge, maybe even bigger if you are going to be more than a couple of feet from your battery. Good luck!

[monstaru]

no subs, no amps, just some lights cb and a deck with some good speaks.the fuse block is going under the hood just about 2 ft from the batteries.so from what you are saying if i have 2 lights on 1 fuse,2 lights on another,the cb and radio can be on one,and the rest will be for add ons i should be alright with a 100 amp max block rated at 30 amps per circiut max..all the jargon of converting this and dividing that really ************s me up.i cannot do simple math but understand the chaos theory? how does that work?cheers mate:grin:

 

All four of those lights together will come in at less than 30 amps, so you're good there, especially if you split them into pairs for fusing purposes.

 

(55+55+100+100) / 13.8 = ~22.5 amps drawn with all four lights on.

 

My HR2510 (10 meter rig I used for CB) was fused at 7.5amps and I had it swinging about 45 watts on a Bird meter; If you aren't going to be running any juice behind it, you are fine on the CB end.

 

The stereo will be fine as well, assuming you are just running a deck. If you plan on running an amp, you've run into a whole new monster, but again, you should be fine as long as you don't go overboard. Are you planning on running subs? Are the main drivers going to be pushed by an amp or just the deck? What amp(s) is/are you planning to run? There is a HUGE difference in rated wattage in various amplifiers, even within a brand. EX: I have an old Rockford Fosgate 500m (rated at 500 watts rms into a four ohm load) that will embarrass newer Rockford amps rated at 1000 watts rms... and will absolutely decimate cheap brand (Pyramid, Boss, etc.) supposedly rated at 2000 and 3000 watts.

 

That said, be sure you have a good, strong source for the block; I'd say at least 4 gauge, maybe even bigger if you are going to be more than a couple of feet from your battery. Good luck!

[nipper]

i understand that is what it means.what i am doing to myself in my brain is by far more involved than it needs to be obviously.and my house is on a 100 amp service.(it's old)what i am trying to figure out is how to take the info already given to me and apply to my certain situation.i work alot, i spend time with my family alot and am generally stressed out..i can read.it does not mean it computes.i am a hands on kind of guy.the overall rating of the block is what i am talking about.to me it makes sense that a block that has 6 circuits,at 30 amp max per circuit should be able to handle 180 amps.but,the research i have been doing states to me that some blocks may have 6 circuits at 30 amp max and only handle 160 amps total.what i am asking is why it is that way.i am not asking for someone to come over and wire my car for me,i am not an FNG.i would like to KNOW what is going on before i start to ************ around with my electrical and modifying it like everything else i have.limits bro,limits.i like to break them,but i do not like fire.

 

CALM DOWN!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

first off if your going to be running 180 amps of anything you need a bigger altenator.

 

Your making yourself crazy. Use whatever fuses you need to use to protect things. do not use a 30 amp fuse on a 5 amp load.

 

I'm bowing out of this one since you seem to be a bit of crazy person , let someone else explain it. i can get deep into materials plastics electrical testing and everything else, but your worrying about it way too much. You didnt even understand my analogy of the light switch.

 

nipper

[zyewdall]

On the rating of the block not being the sum of the individual circuits, that's normal. They are assuming that not everything is on full power at the same time. This is the same way as your house, in which could install a whole bunch of 30 amp breakers, but still can't get over 100 amps total. If you are turning everything on at once, then you either have to not use all the circuits of the block, or get one that can handle all of them on full power. You could also put 20 amp fuses in the individual circuits, instead of 30, and then the total power you can draw is less.

 

The size of the fuse should be determined by what size wire you use. In residential wiring, you're not allowed to use smaller than #10AWG for a 30 amp fuse or breaker. If you've got something that requirest a 30 amp fuse, you better use a #10awg wire. 20amp for #12awg, and 15 amp for #14awg.

 

And yes, if you are running 180 amps for very long, you might want to get an alternator off of a schoolbus, as the subaru alternator isn't really up to more than 30 or 40 amps for very long.

[monstaru]

crazy ,yes.stupid ,no.and i have a 100 amp alt.cheers

 

 

 

CALM DOWN!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

first off if your going to be running 180 amps of anything you need a bigger altenator.

 

Your making yourself crazy. Use whatever fuses you need to use to protect things. do not use a 30 amp fuse on a 5 amp load.

 

I'm bowing out of this one since you seem to be a bit of crazy person , let someone else explain it. i can get deep into materials plastics electrical testing and everything else, but your worrying about it way too much. You didnt even understand my analogy of the light switch.

 

nipper

[monstaru]

damn, an answer.that was way to hard.thanks mate:grin:

 

 

On the rating of the block not being the sum of the individual circuits, that's normal. They are assuming that not everything is on full power at the same time. This is the same way as your house, in which could install a whole bunch of 30 amp breakers, but still can't get over 100 amps total. If you are turning everything on at once, then you either have to not use all the circuits of the block, or get one that can handle all of them on full power. You could also put 20 amp fuses in the individual circuits, instead of 30, and then the total power you can draw is less.

 

The size of the fuse should be determined by what size wire you use. In residential wiring, you're not allowed to use smaller than #10AWG for a 30 amp fuse or breaker. If you've got something that requirest a 30 amp fuse, you better use a #10awg wire. 20amp for #12awg, and 15 amp for #14awg.

 

And yes, if you are running 180 amps for very long, you might want to get an alternator off of a schoolbus, as the subaru alternator isn't really up to more than 30 or 40 amps for very long.

[NorthWet]

Brian, now that you have a simple answer and before you get all Zen-like again , something to consider: Incandescent lights have a high surge current when first turned on; give some extra margin on the lighting circuit(s). (As in, the previously posted math does not apply during transition periods.)

 

I LOVE math!!! It has an answer for everything, including "normal"! (Which, according to math, I am not.) :cool: