10 Gauge Wire

F1118 · Post by **F1118** » Sat Jun 21, 2003 6:22 am

How much current will 10 Gauge Support?

jim · Post by **jim** » Sat Jun 21, 2003 7:07 am

It depends on:

a) length of the wire

b) quality/rating/material of the conductor

Over the length of a run from the underhood center to the trunk, one could expect approx. 30-35 amps RELIABLY with little voltage drop from front to rear. You could theoretically flow more, but most would be lost as heat.

davkenrem · Post by **davkenrem** » Sun Jun 22, 2003 2:55 am

30amps

Jonathan KC8RYW · Post by **Jonathan KC8RYW** » Mon Jun 23, 2003 6:31 pm

Are we talking Copper, Copper-Clad, or Aluminum wire?

There is a significant difference between the three.

davkenrem · Post by **davkenrem** » Mon Jun 23, 2003 6:38 pm

For the distances run in any automobile, 30amps is a very safe number for any modern wire. Especially with only 12 volts. Voltage drop will never be a problem with the distance run in an auto. You could run several hundred feet before you'd have to start factoring in VD losses. Can you even find Aluminum or copper clad wire in 10 guage? I've never seen either in 15 yrs as an electrician.

jim · Post by **jim** » Wed Jun 25, 2003 5:56 am

"You could run several hundred feet before you'd have to start factoring in VD losses. "

Sorry. I disagree- strongly. Voltage drop can be a serious factor in an automobile even with only 5 feet of cable, such as an inverter or alternator. This is why it's critical to use the proper gauge cable for the job. I have seen quite a few cases of a voltage drop of more than 1.0V over a #4 cable of several feet. This is very common of somebody that "builds" an engine and increases the compression, which really loads the starter. The OEM starter lead is no longer adequete for the job. I've also seen many OEM GM products with 100+ amp alternators exhibit more than 0.5V drop from the alternator to the termination point. This is one reason why alternators charge better when cold compared to hot.

If you have a lighting system on a police car running on a single #8 feed, I guarantee there's significant voltage drop on that cable- especially since you can probably feel some heat on the cable in time (which is common to many police vehicles that are cheaply built).

A #10 running to the trunk (12-14') at 30 amps will have drop at this current rating. Key up a 110W Spectra and measure the drop across it's 15 foot cable.

Any drop over approx. 200mv is bad and is in need of a larger cable.

davkenrem · Post by **davkenrem** » Wed Jun 25, 2003 7:57 am

The problem with the starter is amperage draw during starting, I agree with you when you say that increased compression ratio causes the the vehicle to seem to start harder. The increased compression requires more torque from the starter, which in turn creates more resistance and increases the amperage draw. The draw on the starter circuit from a dead stop to full RPM creates a resistance curve that starts relatively high and decrease once the the starter is at speed. Very similar to an AC electric motor, which has much high amperage draw at the start than that of the same motor at operating speed. Obviously the wire should be sized for the expected maximum current requirement.

As for a radio like a 110w Spectra, I really have no idea what the amperage draw would be during transmit. But I purchased a new power cable assm. for a 45 watt Spectra and it uses #10 wire. I would hope the 110w unit uses #8 or #6. but I have no experince with that equipment.

Using the formula to find current, I= E/W = 9.1amps =12vdc/110w.

I can't see why a #10 wire wouldn't be more than sufficient as long as the radio is properly grounded.

Again, I was just applying basic electrical theory to the problem.

If there are other factors to consider in the Spectra equation, I don't know what they'd be.

Also I solved with only 12vdc, most alternaters output a higher voltage.

7.5amps= 14.5vdc/110w.

It the vehicle is running (driving 45mph or so) and the alternater is supplying between 12.5- 14.5vdc. And the equipment is properly grounded, I really don't see why this won't work.

There must be a voltage range that the Spectra will operate in efficiently. ie, from 12.0vdc-15.5vdc. SOme type of upper an lower limit.

Anyone know what that is?

Think about this too, I have a 12v power supply that provides 13.8 vdc at a max of 7amps surge. I can safely run a 45w Spectra without tripping it.

I really think grounding might be the weak link here. If the equipment isn't properly grounded, the current will defiantly increase.

The Police car lighting, what is the total wattage of the cars emergency lighting system? This measurement needs to be done on the battery side of the swith and hopefully it is switched by a relay. This also must include the motors for the rotators and not just the bulb wattages.
Is the vehile running? If it isn't as the batteries voltage decreases, the lighting system amperage will increase.

A Federal Street hawk with 5-55w lamp and 2-35 w lamps has a total of 345 watts of lighting, this doesnt include any motors.

E/W=I

12.5vdc/345w= 27.6amps
Were almost at 30 amps now with just the lightbar .

So the #10 wire doesn't give you any headroom for running the system without the vehicle charging or any other lighting on the same circuit.

I just thougt of something, the loads from the rest of the vehicles equipment is also robbing voltage from the entire system.

Wigwags, Strobes, Lightbar, Radios, MDT.

I think what we were both saying was that wire must be carefully sized looking at the entire vehicle system or the entire system could suffer.

A properly wired radio will suffer in a vehicle with undersized lighting wiring.

nmfire10 · Post by **nmfire10** » Wed Jun 25, 2003 9:34 am

the "110 watts" in a 110 watt Spectra is watts of RF OUTPUT. That number has nothing to do with INPUT.

Average loaded Lightbar: ~30 amps
8 lamp Traffic Advisor fully lit: ~18 amps
Remote Strobes: ~15 amps
Wig-Wags: ~5 amps
Keying up a two-way radio: ~15 amps (variable)
Mobile Repeater: ~2 amps?

That is an EASY 85 amps. 30 amps for the bar can easily be exceeded, as well as the remote strobes. 100 amps of just warning and radio stuff is very easy to do. One 10 gauge going to a "remote battery post" (Your own or one the vehicle already has) or a little bosch relay is not going to very happy with that. Flammbe De Pinto.

davkenrem · Post by **davkenrem** » Wed Jun 25, 2003 10:42 am

nmfire10 wrote:the "110 watts" in a 110 watt Spectra is watts of RF OUTPUT. That number has nothing to do with INPUT.

Hmmm, I'm not sure about that, but that sounds like saying same thing about a 100w lamp. Watts is a measurement of power usage. The amp must do some work to produce the out put power which is measured in watts.

But like I said, I don't have any radio specs here.

But you are so right that trying all the Items you listed on a #10 wire is a fire waiting to happen.

How did you put it?

Flammbe De Pinto

Oh my side hurts.

I think the the intial question was how much amperage can you run on #10 wire.

I answered too quickly, and you guys have answered corrctly stating that it isn't that simply as just knowing what the wire will handle. But more factors come into play when dealing with sizing wire.

I think I've said enough, thanks for the education guys.

nmfire10 · Post by **nmfire10** » Wed Jun 25, 2003 11:45 am

A 100 watt light bub is using the 100 watt electrical INPUT at 120vac as a name.

A 110 watt radio is talking about 110 watts RF Output.

davkenrem · Post by **davkenrem** » Wed Jun 25, 2003 12:33 pm

nmfire10 wrote:A 100 watt light bub is using the 100 watt electrical INPUT at 120vac as a name.

A 110 watt radio is talking about 110 watts RF Output.

No 100w is the power of the lamp at 120v.

At 120 volts the filament has 144 Ohms of resistance, creating 100watts of electric power.

E*E/w= R
120*120/100=144

mike m · Post by **mike m** » Wed Jun 25, 2003 2:05 pm

If I remember correctly the The 110 watt spectra VHF power amplifier is only about 40 percent efficient (.4) and the rest is heat dissipated in the radio chassis.

Ignoring the driver stages and just concentrating on the final RF stage: For 110 watts of RF output the total D.C. power needed to produce 110 watts of RF will be aproximately 110 watts/.4 or about 275 watts.

%eff = Rf output power/ DC supply power or 110watts/275watts = .4 times 100 equals 40% efficiency (just for a check).

275 watts/13.8 volts= 20 amps just for transmitting so lets say an even 20 amps which is just about what a 110 watt spectra needs during intermittant use.

Mike

jcobb · Post by **jcobb** » Wed Jun 25, 2003 2:21 pm

Well, I don't know about all you guys and your pocket computers.

My Spectra pulls 27 amps on transmit. 115w output. So if I put it in my vehicle, I need to plan on 27 amps.

Real world vs. paper.

Jack

mike m · Post by **mike m** » Wed Jun 25, 2003 2:34 pm

jack

Thats worse than I remember, is yours VHF or UHF ? I used to play with older Customs spectras from around 1995 with the HHCH and I remember a little over 22 amps on VHF.

Mike

007 · Post by **007** » Wed Jun 25, 2003 3:08 pm

davkenrem wrote:
Think about this too, I have a 12v power supply that provides 13.8 vdc at a max of 7amps surge. I can safely run a 45w Spectra without tripping it.

I'll pay to see that, because my 45w VHF Spectras draw 12.xx amps on transmit. Even the amateur radio riceboxes that are 50w draw bewteen 10-12 amps.

nmfire10 · Post by **nmfire10** » Wed Jun 25, 2003 3:30 pm

davkenrem wrote:
nmfire10 wrote:A 100 watt light bub is using the 100 watt electrical INPUT at 120vac as a name.

A 110 watt radio is talking about 110 watts RF Output.

No 100w is the power of the lamp at 120v.

At 120 volts the filament has 144 Ohms of resistance, creating 100watts of electric power.

E*E/w= R
120*120/100=144

Excuse me? What? What electrical class did you take? I wish I had these lightbulbs that could "create electrical power". It would save one the bills emensly. I suggest you re-learn some concepts before proceeding. I'll let you do the research, I don't feel like typing it all out here.

100 Watts of power at 120vac is what a "100 Watt Lightbulb" will use. That is a draw of about .83 or so amps.

There is absolutely no corolation between that and the reference to a "100 Watt Radio". When talking about a radio, it is NOT (repeating NOT talking about electrical power feeding the radio. Period. End of story. It is a totally different measurement of (once again) RF OUTPUT POWER COMING OUT OF THE ANTENNA JACK ON THE BACK OF THE RADIO..

Kabiesh?

jcobb · Post by **jcobb** » Wed Jun 25, 2003 4:40 pm

Mike

The Spectras are VHF. The one at 27 amps is putting out around 125 watts, though. I just checked it. It would probably run about 23-24 at 110w.

I have run about 15 thru testing/alignment/programming at my friend's shop - and they all run about what I have listed above.

A hell of a lot more than 7 amps......

My 800meg conventional draws 14 amps at 37 watts. So I doubt that the UHF D44 is drawing only 7 amps. Unless it is set up for "low power"........

My experience has been (although limited) that the higher the output freq, the more efficient the PA. Not linear of course......

Just my 2 pesos worth.

Jack

FMROB · Post by **FMROB** » Wed Jun 25, 2003 5:43 pm

Can't we all just get along!!!!!! In theory if you had a 100 watt appliance operatingin a 13.8 vdc atmosphere it would read somewhere in the 7 amp range draw....No anyone who installs radios knows that the average spectra tuned to almost its capacity 40 watts/100 watts (for hi/low power) will pull anywhere from as low as 6-30 watts. Sooooo, Matt is right, there is absolutely no correlation between the amp draw of a radio in respect to its RF power output...If it was an incadescent light bulb that would be a different story, Then the wattage of the buld would directly relate to the amp draw. What ever the specs are for the amplifier section (it's efficency rating) would be the current draw for the ass end of the radio, i.e. a 30 watt amplifier may draw 6 amps, then add other radio stuff such as the other front end electronics and the total sum of this would be the radios overall current draw. Also, There are many factors that are worked into a "factory specification" of amp draw... In other words of MOTO says X radio will draw 5 amps@30 watts in their techy lit, cable size, temperature, composition of wire, appliance grounding, kinking, efficiency all play a part in the total current draw of an appliance. Some of them may be an extremely small part, but they can add up.

davkenrem · Post by **davkenrem** » Wed Jun 25, 2003 6:04 pm

nmfire10 wrote:
davkenrem wrote:
nmfire10 wrote:A 100 watt light bub is using the 100 watt electrical INPUT at 120vac as a name.

A 110 watt radio is talking about 110 watts RF Output.

No 100w is the power of the lamp at 120v.

At 120 volts the filament has 144 Ohms of resistance, creating 100watts of electric power.

E*E/w= R
120*120/100=144

Excuse me? What? What electrical class did you take? I wish I had these lightbulbs that could "create electrical power". It would save one the bills emensly. I suggest you re-learn some concepts before proceeding. I'll let you do the research, I don't feel like typing it all out here.

100 Watts of power at 120vac is what a "100 Watt Lightbulb" will use. That is a draw of about .83 or so amps.

There is absolutely no corolation between that and the reference to a "100 Watt Radio". When talking about a radio, it is NOT (repeating NOT talking about electrical power feeding the radio. Period. End of story. It is a totally different measurement of (once again) RF OUTPUT POWER COMING OUT OF THE ANTENNA JACK ON THE BACK OF THE RADIO..

Kabiesh?

Hey cool colors. So what your saying if I understand you correctly, Is that the 110watts of RF power has nothing to do with the amperage draw created by the radio while in transmit. I guess I understand that, so the amplifier section of the radio creates a current draw by what means?
Hey I never claimed to be an electronics expert, just an electrician.
Please educate me a little.

I understand now that the RF wattage rating has nothing to do with the amperage draw of the radio.

What circuit in the radio is cause the resistance to raise the amperage. If it is the amplifier section, then there is something in there who's output is measured in wattage, right?

Like I said in my eariler post

If there are other factors to consider in the Spectra equation, I don't know what they'd be.

As for "getting along", I hope no one is getting angry at this topic, I think nmfire is just shouting cause I still havent grasped what he's teaching me.

Everything is amicable from my view and I'm really enjoying this conversation.

jcobb · Post by **jcobb** » Wed Jun 25, 2003 6:19 pm

You're talking apples and oranges.

The RF energy put out by the radio is the equivalent to "lumens" put out by the light bulb.

Just as there is no "formula" for computing lumen output of a lightbulb for voltage/watts rating, there is no set formula for computing amp draw for a given RF wattage output.

No radio PA is 100 per cent efficient, or even close, therefore some of the energy is dissipated via heat. That's what the heatsinks on the back of the radio PA is for.

Most of us go by the empirical data we gather from actual usage; the "laboratory" figures given by the manufacturers are just that - guidelines.

And if you are transmitting on the UHF Spectra, it must be set up for low power.

Jack

nmfire10 · Post by **nmfire10** » Wed Jun 25, 2003 6:35 pm

More RF OUTPUT wattage will create a need for more ELECTRICAL INPUT wattage. However, they are by no means equal, proportional, or consistant. They are totally seperate entities.

FMROB · Post by **FMROB** » Wed Jun 25, 2003 6:48 pm

Matt, You are correct again, However they are separate entites, but all are in some form equal, and proportinal, Otherwise would have no basis on which to rate our power comsumption, loss, gains, and otherwise. Just an observation....Not for nothing guys, but this isn't exactly the most intersting topic on the planet....So how about those Mets......Just kiddin..Later

nmfire10 · Post by **nmfire10** » Wed Jun 25, 2003 7:00 pm

I should re-phrase that. They are no consistantly and/or equally proportional. They are proportional to the extent that in general, higher output will draw a higher input. How much higher variers depending on a million different factors.

F1118 · Post by **F1118** » Wed Jun 25, 2003 8:06 pm

Ok, well than 10 guage will work fine for what im doing....Im running about 12 feet from the battery to a power distribution panel....than running power to a 45 watt spectra, a 50 watt icom, a scanner, and self contained strobes. Sounds like even for a 110 watt spectra I would need to run another line but I dont have one of those yet. How much will a 45-50 watt radio pull just powered on and recieving?

kf4sqb · Post by **kf4sqb** » Wed Jun 25, 2003 8:08 pm

Just my $0.02 worth: for any high-power mobile radio (or any load around 30 amps or so), I personally would not run anything under #8 copper (app. 40 amps up to app. 50') from under the hood to the trunk/rear of a vehicle. For 20 amps, #10. For 10 amps, #12. I realize that this is often times overkill, but these sizes will allow a generous margin for error. You get more voltage drop that you think from the battery to the trunk of a car, and voltage drop can sometimes cause strange problems (overheating of equipment, blowing of fuses due to excess current draw, overheated wire, fires, etc....).

FMROB · Post by **FMROB** » Wed Jun 25, 2003 8:19 pm

I wouldn't use 10ga. If you want to do it right, Bigger is Better,,,,Super Size It, With a Large Coke.....Go for nothing less than a 8 ga. cable. It may be overkill, and not required for your estimated current consumption, but why chance it. It will cost marginally more, but might save you money in the end by avoiding any damage to components (not saying anything would happen with the 10ga..)....Good Luck.

P.S. I have all undercover equipment as far as lights go, here it what my pov has with a 4/0 cable from battery, circuit breaker, then to a interior distribution block.
1- Whelen ISP188, 180 Watt Strobe Supply
2- Whelen LED Slim Lighters
2- Whelen LED 4E Series
1- Whelen HD Flasher UHF2150A
1- Motorola Siren Unit
2- 18" White Florescent Work Lights
2- Whelen Halogen HALGRL under Rear Bumper
1- UHF 40 Watt MCS2000
1- Low Band 100 Watt Syntor x9000
1- UHF VRS
1- 800 Mhz Spectra
1- 40 Watt VHF Spectra
1- Nextel Handsfree Kit
1- Sony XM Sat Radio

No problems at all,,,,,Works like a champ...I have let my vehicle idle with all of the lights on while using my Syntor VRS at brush fires and hazmat calls for hours on end....Not one hint of any overloading.

k4wtf · Post by **k4wtf** » Tue Jul 01, 2003 1:25 am

F1118 wrote:Ok, well than 10 guage will work fine for what im doing....Im running about 12 feet from the battery to a power distribution panel....than running power to a 45 watt spectra, a 50 watt icom, a scanner, and self contained strobes. Sounds like even for a 110 watt spectra I would need to run another line but I dont have one of those yet. How much will a 45-50 watt radio pull just powered on and recieving?

I'd go 8 guage minimum if I were you. You need to calculate what the max possible draw will be from your distribution panel. Either that or fuse the INPUT of the panel at the max rating of the wire you use. Also don't forget to fuse/breaker at the battery connection.

---
John

ricciticcitembo · Post by **ricciticcitembo** » Tue Jul 01, 2003 5:40 am

Oh my goodness gracious this thread is Hilarious, even by my standards.

I vote this one into the funniest threads of all time.

I tie my sneakers with 10 gauge.
That and Shoelaces have about the same electrical capacity when
talking about running multiple Items from the same 10 gauge wire.

Like Jim said any drop over a couple hundred millivolts is a No-No.

DUH.

But that must have flew over their heads like rocket. I guess it's
apparently Not that obvious.

And using a calculator to install your radios is another No-No, as
Jack pointed out already.

Why not just get it over with already and just use some 18 gauge
zip cord with a cigarette lighter plug on it??

That oughta run a couple of Spectras and a few scanners.
Plus you might be able to still light a cigarette when transmitting.
Now how cool would that be?

Use a lot of magnet mount antennas also. They're the best.

Just make it look like a ham radio mobile, and you'll be A-OK.

The Hard Truth is I've seen lots of them that have like one 10 gauge wire to a distribution block and about 8 radios. Oh Boy Oh
Boy does that ever work well. I'll tell you these ham radio geniuses
really know how to save. It's nice to see Public safety doing the same.

tiredfireman · Post by **tiredfireman** » Wed Jul 16, 2003 12:25 pm

Man oh Man, what a debate. Darn near busted a gut laughing at a couple of you duelers.

Seems here is a classic example of why "electricians" (120volt guys) don't play well with DC types.
See.. using 'tried + true' guidelines for 120v apps just doesn't cut it for 12. Acceptable losses in the 120 world are a couple of volts in a long line, like an extension cord (just check out the labels on the orange Homey Depot stuff -- 5volts). So we're in the neighborhood of 4-5% (don't yell, math is rusty - calculator dead) BUT 4-5% of 12 (really 14) volts is MUCH less. Losses of a couple of volts in the mobile world are not acceptable. Even if you manage to make it work while running, you may find stuff drops out (from low volts) with the key off, even tho your trusty voltmeter says 12 at the batt. Good grounding can't hurt, but is getting tough to find in plastic vehicles, which is why alot of stuff comes with its own heavy ground wire ( to be cut short and screwed to the plastic dash!)
The raging debate over lightbulbs vs radios is borderling hilarious.
The calculator types (yes I can spot youse) figure mathmatically that the 100W bulb works out to a fixed resistance -- nice in theory, but the filiment actually will change resistance (impedance, anyone?) with voltage changes - or, as it gets hotter or cooler. But it will consume roughly 100 watts of power fairly consistantly. HOWEVER, to produce 100 watts of radio frequency power (OUTPUT) a lot of power consuming 'magic' goes on in that little black box AND, as some pointed out, power conversion is NOT yet at the 100% perfect stage, so lots is wasted as heat.
So, whats the bottom line?? If your rig comes with a 20 amp fuse and a 12 ga. wire, if you've got a long run, up the size of the wire one notch to 10 -- and resist the urge to hang on options after the fact!! Read your specs section of your manual It'll tell you what the radio draws keyed. Lost it?... Beg, borrow, or otherwise obtain a 50 amp (DC!) ammeter and measure it at the posts.

I would strongly recommend searching out some AUTOMOTIVE wire guidelines to send you in the right direction. Also, WEST MARINE has a real good chart that includes your return (ground) lines in the mix to come up with a proper sized wire. Overkill to some, but it beats ripping out and re-installing, and with plastic car bodies wiring is getting to be damn near like a fiberglass boat anyway.

And another thing (you thought I wuz done?) BEWARE of using circuit breakers under the hood. My department had a "professionally done" installation of lights/sirens/radios in our chief's truck, with an HD marine circuit breaker protecting the feed to the console. Excellant idea you say.
Except that the day it was put into service was in August and the underhood temps approached that of the Sun. So, as I was motoring accross a 4 lane by 4 lane intersection against the red, I thought it was odd that I lost me siren when I keyed the radio. Guess what? Lost the siren, lights, radios, and everything not 'factory' in the gig. How I didn't get killed is still a mystery. Fortunately the trusty portable hit the repeater to code OOS. The installer's reply?? Wow, you're the 5th customer to have the same problem. Know what? All that neat paperwork that came with the circuit breaker listed the DERATINGS at various high temperatures

So, my 80 amp breaker was, at best, a 40 amp at underhood temps and wasn't even self resetting. I was not amused. But.. stuff happens, right. Peruse your paperwork, come to a sound conclusion, and add a wire size for a "fudge factor".

So what? Playing it safe has never hurt me (or anyone else) in some 20 years of wiring emergency vehicles (and no, I'm not a 'professional').
BUT, after you finish decking out your pride and joy, don't forget that fire extinguisher

HALON RULES, but a good 5 pound ABC is cheaper.
Stay safe. Thanks for the oppurtunity to 'spout'.

ssybert · Post by **ssybert** » Tue Dec 02, 2003 11:28 am

I know this is an old post, but I was searching for some info on Power limits for different guage wire and couldn't really find anything sold or useful here. I turned to google and found this. Maybe it'll help others in the future.

http://www.powerstream.com/Wire_Size.htm

key words: wire guage size power handling handle limit amp amps

apco25 · Post by **apco25** » Tue Dec 02, 2003 12:19 pm

THis sillyness is the reason my truck has 2 power feeds, front and rear rated at 100 and 250 amps to each.

Same reason I stayed away from circuit breakers this time and went with HI-AMP heavy duty fuses.

Tom in D.C. · Post by **Tom in D.C.** » Tue Dec 02, 2003 2:02 pm

RMS versus DC, anyone? (G)

Tech225 · Post by **Tech225** » Tue Dec 02, 2003 3:42 pm

See if this helps. If nothing else it is handy to have.

http://www.wranglernw.com/wire/

nmfire10 · Post by **nmfire10** » Tue Dec 02, 2003 4:20 pm

Oooh. The lightbulb vs Spectra thread. I remember this, that was funny. On that note...

My cat's breath smells like cat food.

ROSDJS · Post by **ROSDJS** » Wed Dec 03, 2003 3:51 pm

If I were going to be sending a battery to trunk run I would just make life easy and go overkill. When in doubt just go over. Try going to a place that sells stereo equipment and get a piece of 1 guague or 0 guage used for an amp kit and run it to the trunk. You've got plenty of room for additions in the future that way too....just my 2 cents.

Matt

Matt · Post by **Matt** » Wed Dec 03, 2003 6:41 pm

This site has a few tools (Calculators, Charts, Diagrams, etc...)

http://www.the12volt.com

10 Gauge Wire

10 Gauge Wire

10 ga wire

This here thread...