> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
> Behalf Of Bill Turner
> Sent: Sunday, November 13, 2005 2:35 PM
> To: amps@contesting.com
> Subject: [Amps] Question about safety ground connection
>
> I have a question about how to connect the safety ground from the AC
> mains.
>
> I'm building a 1500 watt amplifier with a separate power supply. The
> power supply will connect to a 120-0-120 wall socket. My question is
> whether the "0" pin is considered a safety ground pin or a neutral
> pin. If it's neutral, then do I have to run a separate safety ground
> wire back to the AC mains entrance? Conversely, if it's a safety
> ground pin, am I allowed to connect a 120 volt load (blower motor)
> from it to one of the 120 wires? I suspect not, so does this mean the
> 120 volt load will need its own separate 120v circuit (with its own
> ground), and is it ok to connect the two grounds together?
>
> Comments appreciated.
>
> 73, Bill W6WRT
>
Hi Bill,
At the risk of starting another AC ground / neutral war,, it is always ok
to connect any grounds together. It is not ok to connect a neutral and
ground together except at one place, the main service disconnect box.
If you are going to run a power line to your amp run 4 wires from the power
panel. If you are going to use an existing 240 outlet it depends on what it
was installed for as to how it is wired.
If it is an electric stove outlet with 3 wires it will be 2 hot and a
neutral. A stove outlet must be a dedicated circuit so that means that the
neutral is also tied to ground at the service panel. So you could use it as
either a neutral or as a ground, but shouldn't use it as both even though
the stove does. A stove was one of those "special exceptions" in the nec
code. The new code now requires 4 wires for the stove.
If it is an existing 240 volt air conditioner outlet it will most likely be
2 hot and a ground. No neutral.
If your amp is going to run on 240 volts you do not need to wire a neutral
to the power supply. Some amplifiers run the fan motor from one hot leg to
the center tap of the primary of the power transformer. This provides 120
volts via auto transformer action of the transformer primary. This works
fine if the 120 volt load is not too great as in running a fan. Otherwise
you need to run a neutral wire for the fan and then use one of the hot lines
from the 240 for the other leg for the fan. This would require 4 wires.
Safety ground should never carry current.
73
Gary K4FMX
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