Emergency Circuit Isolation; Total Circuit Isolation - Generac Power Systems GR-210 Operation And Maintenance Manual

DANGER! A hazard exists during a power out-
age if the generator is connected to building cir-
cuits and no method of positively isolating the
generator from the utility supply is provided.
Power company workers attempting to restore
utility power will open a switch between the
main power supply and the spot where they are
working. If the home or building electrical cir-
cuits are not isolated from the utility supply,
generator AC output will backfeed through the
building electrical circuits and up the power line.
A power company worker may be electrocuted.
If utility and generator power are not isolated
and utility power is suddenly restored while the
generator is powering load circuits, the genera-
tor can be severely damaged.

EMERGENCY CIRCUIT ISOLATION

One isolation method is to have emergency circuits
(important or essential items to be powered during a
utility outage) grouped together and rewired into a sep-
arate "emergency distribution panel" (Figure 3). Using
this method helps prevent accidental overloading of the
generator or the specific generator receptacle in use.
Loads fed by this emergency distribution panel must
not exceed the wattage/amperage rating of the generator
or the specific receptacle in use.
A transfer switch having an ampere rating equal to or
exceeding the ampere rating of the emergency circuit
should be connected between the building's main elec-
trical distribution panel and the emergency distribution
panel.
6 Generac Power Systems, Inc.
®
General Information
GR-210 Generator Set
Figure 3 - Emergency Circuit Isolation
*Ampere rating must be equal to or exceed the ampere rating of the emer-
gency distribution panels.
**Ampere capacity not to exceed the alternator rating. Only these items will be
powered by the standby alternator. If the electrician sizes the load properly, the
alternator cannot be overloaded.
All wiring must conform to the United States National Electrical Code (NEC)
and all state and local codes. Consult a qualified licensed electrician.
The above illustration assumes the utility is supplying 120/240 volt single phase
electric service.

TOTAL CIRCUIT ISOLATION

If the emergency circuits (Figure 4) are not or cannot be
wired together in a separate emergency distribution
panel, you will have to select the circuits and specific
appliances to be powered by the generator during a util-
ity power failure. When this is done, take care to avoid
overloading the generator or generator receptacles.
When using the total circuit isolation method, the
ampere rating of the transfer switch must equal the rat-
ing of the normal incoming utility service.