This discussion brings up a related issue: what's the best choice for a
220VAC outlet for an amplifier and how should it be wired?
Locally, I've been able to find two surface-mount NEMA outlet boxes for
220VAC: the 4-blade type (two flat blades, one angled blade and one curved
blade ), and the three-blade type (two blades at an angle to each other and
one angled blade.) So far, I've been able to find a separate plug for the
four-blade type, but only complete cable assemblies with a molded plug for
the 3-blade type (I live in the boonies, folks.)
Both of my amps (87A and SB-221) are set up for 220VAC and have three wires:
two black hots and one green ground. Best I can determine from the
schematics, the green ground wire is connected to the chassis on both amps
and functions as a safety ground only. I also have a ground strap running
from the ground lug on each chassis to the station single-point ground
(lightning and so-called RF grounding). The 20A 220VAC service to the shack
has four #10 wires: black and red for hot, white for neutral and bare for
ground.
I'd like to use the four-blade box for one amp and the three-blade box for
the other. It seems to me that I should connect all four service wires to
the 4-blade box, but for the amp connected to that outlet I should connect
the amp's ground line (green wire) inside the plug to the ground blade (the
angled one?) and *not* the neutral blade (the curved one?) -- effectively
leaving the service neutral wire in the outlet box unused. For the 3-blade
box, I think I should run three wires to it from the 4-blade box, connecting
the black and red wires to the flat blades and the bare wire to the angled
blade. Then I should connect the second amp's green wire to the angled
ground blade on the plug.
Bottom line, the service neutral won't be used at all (it wouldn't even be
run from the 4-blade box to the 3-blade box.) It seems to me that if I did
connect the neutral wire to the amp green wires, then the neutral and house
ground would be connected through the equipment cabinets in the shack. Since
this is a point other than the service entrance, the outlet wiring would
violate the code.
Is this correct and are my wiring plans OK?
73, Dick, WC1M
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