Seems a lot of folks have opinions and that is a good thing. Perhaps I
am just a little more anal about keeping wires cool (yes, I HAVE had a
house fire). Fortunately it wasn't caused by under sized electrical service.
Gudguyham@aol.com wrote:
>
> >In a message dated 10/18/2005 8:22:50 PM Eastern Daylight Time,
> >aa4lr@arrl.net writes:
>
> > >W4ZT wrote:
> > > Now let's try 240 volts
> > > which would give us 2944/240=12.3 amps. If your line voltage is
> > > low and
> > > you have 220 volts the current would be 2944/220=13.4 amps. From this
> > > example it is obvious you can't run a full legal limit amp on even
> > > a 20 amp, #12 wire, 120 volt circuit much less any 120/240 volt, 15
> > >amp #14 wire circuit.
> >
> >Seems to me that 12.3 A and 13.4 A are both less than 15 A. So a #14
> >circuit seems adequate for your example.
>
> FYI....An Ameritron AL-1500 will do 2300 watts output with 100 watts of
> drive. (FACT)
> The AL-1500 comes from the factory with a power cord with a 240V 15A
> power plug and is fitted with 15A fuses. A 240V circuit run to this
> amp using #12 wire will run this amp at 2300 watts out with no problems
> in SSB and CW modes. Surely a 15A circuit will suffice at legal limit.
> The important thing here is the length of the run from the service panel
> to the outlet for the amp. If your voltage is way low, the Ameritron
> has a low voltage tap you can use which ups the secondary voltage so
> that current again is not an issue. An amp such as an SB-220 can easily
> be run on a 240 line run with #14 wire.
If we use your factual example of 2300 watts OUTPUT, then using 60%
efficiency will give us 3833 watts input power, add a few amp pieces for
another 100 watts for 3933 watts. Use 90% efficiency for the power
supply and you've got 4370 watts. That's 18.21 amps at 240 volts. Add a
blower at an amp and you're up to 19.21 amps. #14 wire on a 15 amp
circuit wouldn't be the right choice for your example. Actually, neither
would #12 on a 20 amp circuit. Drop the mains voltage, change the tap in
your power supply to maintain your B+ and your mains current is even higher.
This is why I went through the exercise in the first place. There are
always a few hidden current consumers in the amp and if you then choose
to power the transceiver or other things from half that circuit you're
unbalanced and higher yet. I wasn't trying to start a high level debate
just a practical example of why a little larger wire is better.
Each of us has to decide how much risk we're willing to take.
73, Tony W4ZT
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