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Correcting Multi-wire Branch Circuit Wiring
976-0043-01-02 F–5
Correcting Multi-wire Branch Circuit Wiring
Acceptable options Correcting multi-wire branch circuit wiring is not easy. Two options
which will correct multi wiring branch circuit wiring are:
• Rewire existing multi-wire branch circuits to conventional “home
run” wiring. This requires a qualified electrician (knowledgeable
about multi-wire branch circuit wiring) and is expensive. There may
be multiple multi-wire branch circuits located throughout the
structure, requiring complete rewiring.
• Add a second inverter in a “series stacked” arrangement. This is an
expensive solution, but would restore the original 240 Vac split-phase
configuration. This solution may actually be less expensive than
having an electrician re-wire the multi-wire branch circuits. It also
provides increased power backup protection and can power 240 Vac
loads.
Recommended
option
Add a step-down autotransformer to the output of the inverter to restore
the split-phase configuration. This is the least expensive and easiest
method to correct for multi-wire branch circuit wiring. Refer to Figure F-
5. Using this method, half of the current is supplied to one leg of the
circuit and half to the other in a split-phase arrangement (180° out-of-
phase). This will restore the original functionality and safety to the multi-
wire branch circuit.
WARNING: Fire Hazard
Until one of the solutions above is implemented, a stand-alone 120 Vac inverter
(or generator) must not be installed where multi-wire branch circuits exist.