Ken and the group,
I subscribe to "ECM", an Electrical Contractors' magazine. It has a
monthly feature on Electrical Code application. Generally, in something
like an existing electrical dryer installation with 3 wires; one being
the combined neutral/ ground; the installation would be grandfathered.
Only if the whole house was being remodeled and major changes being made
to the electrical system requiring a local authority inspection would it
possibly have to be changed. And even so, the local authority having
jurisdiction can adopt all or part of either the newest electrical code,
or a prior issue of the code. (I think there is a limit on how far back
a code edition can be used.) The code is always changing, usually to
clarify contradictions and add useful new developments, such as some
years ago when GFI technology was introduced to protect outlets in at
risk areas. (Ground Fault Interrupter detects current flow exceeding
safe limits on the green wire, and trips out that outlet and any beyond
it on the same circuit.)
If you were to hook up a new 240 volt appliance that does not use direct
connection of 120 volts to the incoming line, you would have no current
in the third wire. Since the safety ground is bonded at the main panel
to the Neutral bus even if you have an older appliance using half of the
240 Volt feed for motors, you are still safe.
-Stuart Rohre
K5KVH
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