Hi All,
John is correct. See NEC 250.138 and 250.140. It was common in old
equipment (my Heath SB220 is a good example) to have the control
circuits (PTT Relay) use the grounding (green) conductor for a
return. No longer permitted.
4 conductor plug/receptacle required. The green wire (grounding
conductor) is just that - grounding. Referencing the dryer example,
for old dryers, NEC says you must disconnect the bonding between
neutral (the 120V stuff) and the cabinet grounding conductor within
the dryer even with the 4 prong plug.
Basically the green wire is only a safety ground. There should never
be any circuit current flowing through that conductor.
Hope that helps.
Regards,
Larry
At 08:50 PM 10/30/2006, you wrote:
Hi Jim,
I understand that the update to the National Electrical Code now dictates
that all NEW work 220V outlets have a neutral in addition to the ground. This
makes good sense, especially in light of your email. Buy the way,
legal or not,
The Collins 30S-1 amp had an internal 120V outlet under a shelf in the power
supply. This was to facilitate installing the power supply for a
KWM-1 within
the amplifier PS cabinet. I don't doubt that other manufacturers and
homebrewers do similar things with blowers, relays and control
circuits. Dangerous? I
suppose under the right circumstances it could be. For once, I can go along
with the NEC folks.
73 and stay safe,
John, W4AWM
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