Correcting Multi-wire Branch Circuit Wiring
975-0012-01-02 Rev A C–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 C-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.