Hi Carl,
It appears there may be some confusion about what a neutral
and a ground are.
A neutral is a lead sized to carry return currents to the
mains box, and it is an insulated lead. In a consumer device
it carries current.
The ground is normally a bare conductor of smaller size, and
it also connects to the ground buss in the mains panel.
The difference is ALL wiring codes in the USA do not allow
the safety ground to be used for mains current return. They
must also be isolated, and connected ONLY at the mains box.
This is in sections 250-60 and 250-61 of the National
Electrical Code.
This is in sections NEC Sections 250-60 and 250-61
> So then you are trying to convince us that anyone who has
> a 240V dryer, range, AC, Air Compressor or similar device
> with the neutral tied to the ground at the wall outlet and
> at the device has a safety issue.
That's correct. If it has a current carrying neutral tied to
ground at the outlet it is illegal.
Only non-current carrying grounds for safety can connect to
the outlet ground.
> Sorry Tom, but the NEC manual disagrees with you and Id
> much rather follow what the experts say.
I suggest you read sections 250-60 and 250-61 of your
manual.
> And I have yet to see any 240V single phase ham amplifier
> manufacturer provide a 4 wire cable.
Well Carl, that's because they do NOT connect any current
carrying path back to the third wire. If the manufacturer is
stupid enough to tie a 120V filament transformer return to
the power neutral, then the amp would have to have a four
wire plug OR that neutral would have to float from the
chassis and meet voltage breakdown isolation requirements.
You won't find a properly designed for USA sales commercial
amp anywhere that ties a blower, control, or filament
transformer return to the chassis.
> In looking thru my amp manuals going back 40+ years I see
> that all 240V configurations show the neutral connected to
> chassis ground. This, strangely enough, includes Ameritron
> and verified with the AL-1200 on the bench for repairs.
You are wrong.
The AL1200 does not connect any part of any of the
transformer primary wiring to the chassis. There is NO
neutral to chassis connection. That center pin on the three
wire cord carries no current, and is a GREEN wire intended
to be a safety ground only. It is intended to be wired to
the safety ground of the outlet. You will not find a single
Heath or Ameritron amp that uses the chassis as a AC mains
return for any internal power. You will not find a dryer or
other device that meets UL or NEC specs that has power
returned through a connection that is common to the chassis
or the power mains safety ground.
That plug is a NEMA 6-15P plug Carl. You can find it at this
link:
http://www.levitonproducts.com/catalog/sort_NAME/dept_id_969.htm
Notice it says it is a TWO-POLE 3 wire grounding plug.
If you read this link:
http://en.wikipedia.org/wiki/NEMA_connector#NEMA_10
it will explain the proper use of power plugs.
I think the problem with the AL1200 is you don't fully
understand the difference between a mains neutral and a
safety ground. There is a direct connection to the chassis
of the third round pin on the cord, but operating current
exclusively passes between the two flat blades, the two hot
poles. If there was a blower or transformer inside the amp
connected to the chassis, it would fall out of code
compliance. It would require a NEMA 14 plug with THREE poles
and a ground.
Without the NEMA 14 plug, if the neutral would open in the
house wiring or cord the amplifier chassis would then have
120V on it, and if someone was hurt they would win a lawsuit
hands-down. Worse yet, if someone who doesn't understand the
difference between the safety ground and the power mains
neutral tied the two together and there was a neutral fault,
it could energize other complying devices.
Reading the wikipedia link above should clear this all up
for you.
73 Tom
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