- Q.How do you wire a four-wire
240-volt appliance (kitchen range or dryer) if there
used to be a three-wire appliance there?
A. You’re probably
better off calling an electrician; but if you plan
to do the work yourself, first determine if the
appliance is fed from a main panel or a subpanel.
If the feed is from a subpanel, you must install a
new four-wire circuit to the appliance to comply
with code. Bonding the neutral (grounded circuit
conductor) and the ground wire anywhere but at the
main panel is a big no-no. If the feed is from the
main panel, you can connect the ground wire
attached to the frame of the unit (green or bare)
to the neutral terminal on the terminal block and
change the pigtail to a three-wire type. But when
possible, installing a four-wire circuit is still
preferable.
Here in the Southwest, most houses are built
slab-on-grade and have flat roofs. If you
don’t have an attic or crawlspace, and the
appliance is on or near an exterior wall, you can
install new conduit on the exterior. Between the
exterior wall and the appliance, there are often
cabinets behind which you can hide conduit, with
little intrusion or patching. Flexible conduit can
be helpful here.