Hi I have NM Romex 12/2 with ground currently running from my panel to
a wellhouse and it's setup for 110 which is running one outlet for a
light and the well pump. I need to install a new pump but it requires
220v. Assuming I convert my breaker to 220, can I use the existing
12/2 romex for the new outlet in the wellhouse or do I need to run
You can use the existing 12/2, but you'll have to dump the outlet /
light since you won't have a valid neutral, just two hots (marking the
white wire with red tape as the other hot) and a ground. You could
potentially use a 220V light, such a commercial fluorescent or HID unit.
He could also use a transformer to derive enough 110V for a lightbulb.
Or, a two-lamp fixture could be rewired in series; the white wire from
each lampholder tied together would float, so the two bulbs would need
to be the same wattage. (UL might not approve of this.)
Putting a 220V ballast in a fluorescent shop light might be the best option.
But in this case, you wouldn't have 2 hots and a neutral, he'd have 2
hots and a ground and no neutral. The existing neutral wire is being
converted to a hot wire. With a few *very* specific (and obsolete but
still grandfathered) exceptions, a grounding wire and a grounded wire
(neutral) are not the same thing.
Salvaging the 12/2wg cable (are you sure it's NM and not UF?) is not
worth doing the job wrong. Now if it was 10 gauge cable and there's a
metal well casing in the pumphouse, it would be tempting to put in a
little 30A service entrance rated subpanel and overlooking the bare wire
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