[HCARC] 12 Volt vs Wire Size Website

Wed Sep 19 17:18:49 EDT 2012

Dennis, et al

As I tried to explain before the radio is going to be served from two 6 volt 
deep cycle golf Cart batteries conneccted in series to give 12-14 volts. 
That is the power supply in question.  I don't know if Dealers Electric 
carries 12 volt fuses and fuse holders - I doubt it, but haven't checked. 
Currently there is no AC current involved in the project at all.  The radio 
has a max draw of 13.8 volts and 20 amps at full key down transmit. 
Elecraft says to protect the DC circuit from the battery to the radio with a 
25 amp DC fuse on both the positive and negative leads from the battery. 
Since I have about 1850 feet of #6 wire I'd like to be able to use some of 
it, and yes for up to 25 feet (12.5 on each leg) the #10 is rated as 
sufficient.  I was looking for a fuse that I could use with a holder that 
would accept the #6 wire.

The mat and the wrist strap both have a wire and an alligator clip to 
connect to ground.  I was just trying to assure myself that the 8 foot 
ground rod sunk in the wet ground next to my house would be an adequate 
ground to connect the clips to.  I was also wondering how or if it were 
possible to check and see how good the ground (or any ground for that 
matter) might be.

My service is connected and checked by Bandera Electric to be in compliance 
with their requirements.  Some guy from Comfort who apparently is on the 
Reflector, but not a club member tried to tell me that my system is not as 
it is.  Since I built my own home and did the wiring myself I know it is to 
code - in fact the wire is sized up in excess of code as I figure that in 
electricity larger wire is always better.

Gary J
N5BAA

----- Original Message ----- 
From: "Dennis Robertson" <robertson at ctesc.net>
To: "Gary and Arlene Johnson" <qltfnish at omniglobal.net>
Sent: Wednesday, September 19, 2012 3:47 PM
Subject: Re: [HCARC] 12 Volt vs Wire Size Website

> Gary,
>
> Several answers---
>
> Number 10 wire is rated to carry 30 amps or more depending on the type of 
> insulation on the conductor.  [think 30 a for DC use]
>
> Most DC power supplies that you might use are not rated much over 30 amps 
> with a little extra surge capacity so there is no need to
> oversize the wire beyond # 10 unless you are running a long distance.  If 
> that is the case, it would be better to move the power supply
> closer to the load and extend the 120vac service.
>
> You should be able to find commercial type fuse holders at Dealers 
> Electric in Kerrville.  Most fuses that fit these holders will carry a 
> 250vac
> rating in various amperage sizes.  The voltage rating relates to the 
> voltage that the fuse will clear in a fault condition [bigger is better].
>
> Also, most of the radio equipment that is commonly used today draws 
> between 20 to 25 amps so there is another reason not to oversize.
> It is not uncommon to have a seperate power supply for each radio.
>
> Your question concerning static discharge while working on circuit 
> boards--use the mat and wrist band to prevent and difference in voltage 
> between
> you and the radio.  An external connection to building ground can be used 
> if desired but is not necessary.
>
> Your question about ground rod--the 5/8" X 8' rod is the standard size rod 
> used in association with meter loops for commercial power.
> The National Electric Code requires a resistance of 25 ohms or less from 
> the new rod and some reference point.  That could be metal water pipe,
> the ground on your power pole, or any point that is known to be grounded. 
> High quality low range meters are used to check ground grids in power
> facilities because the resistance is typically fractions of an ohm.
>
> On your ac wiring in your house--the white wire [neutral] is a grounded 
> conductor that carries current and some voltage on a two wire circuit.
> In a multi-wire circuit where two hot conductors share a common neutral, 
> the neutral carries the unbalanced current.  Note that the two hot 
> conductors have to be on different phases such as L1 & L2 [240vac] from 
> your panel.  If the two hot conductors come from the same phase then the 
> neutral will carry the total
> current of the circuits.  This is a dangerous condition that could lead to 
> a fire.
>
> You will note that I called the neutral a grounded current carrying 
> conductor earlier.  The ground wire [green] in your house wiring is also a 
> grounded but does not carry current except under a fault condition.
> The only place where these wires are connected is on the center terminal 
> of the meter socket.  The neutral wire from the transformer, the neutral 
> going to the main disconnecting device, and the ground wire to the pole 
> ground or external ground rod are joined at this location and no where 
> else on the customer side of the meter.
>
> Hope this helps,
>
> 73's
>
> Dennis  KC5PQN
>
>
> ----- Original Message ----- 
> From: "Gary and Arlene Johnson" <qltfnish at omniglobal.net>
> To: <hcarc at mailman.qth.net>
> Sent: Wednesday, September 19, 2012 10:26 AM
> Subject: [HCARC] 12 Volt vs Wire Size Website
>
>
>> http://www.offroaders.com/tech/12-volt-wire-gauge-amps.htm
>>
>> As many of you know, I have been planning to run my new K3 off of battery 
>> power in order to become proficient at it so I can run a "Green Power" 
>> station at the next Field Day.  I have been looking for fuses and fuse 
>> holders in a large enough size to wire the station using 6 gauge wire 
>> that I have plenty of.  I have not been able to find the fuse holders 
>> capable of being wired into a 6 guage wire system.  My next thought was - 
>> how much overkill am I working with by going to 6 gauge wire??  I found 
>> this website that tells me I am overkilling the wire requirement by a 
>> lot. This website says I can safely use 10 gauge wire for 20 amps up to a 
>> 25 foot run.  That solves the problem as long as I am electrically safe, 
>> and fuse holders with 10 gauge wire leads are easily found.
>>
>> Gary J
>> N5"BAA"
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>
>
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