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2012 Magnum Energy, Inc. Page 36
Installation
2.10.2 Equipment Grounding Conductor
The MMP enclosure and all other noncurrent-carrying exposed metal surfaces in the entire electrical
system that may be accidentally energized must be grounded. The equipment-grounding conductor
must be sized to safely carry the maximum ground-fault current likely to be imposed on it from
where a ground-fault may occur.
AC Side – When the AC circuit breaker provided in the MMP enclosure is being used as the
inverter’s AC overcurrent protection device, the AC Equipment Grounding Conductor (EGC–AC)
for the inverter is based on the AC breaker size provided (#10 AWG for all MMP models). Connect
the AC equipment-grounding conductor from the inverter’s AC ground connection to the Ground
Busbar (GBB) in the MMP enclosure (Item 8 in Figure 1-2 or 1-4).
DC Side – When the DC circuit breaker provided in the MMP enclosure is being used as the
inverter’s DC overcurrent protection device, the DC Equipment Grounding Conductor (EGC–DC) for
the inverter is based on the DC breaker size provided (#6 AWG for MMP175 models, #4 AWG for
MMP250 models). Connect the DC equipment-grounding conductor from the inverter’s DC ground
connection to the Ground Busbar (GBB) in the MMP enclosure (Item 20 in Figure 1-2 or 1-4).
If you are using AC or DC overcurrent protection that is different than that provided in the MMP
enclosure, or installing optional DC breakers inside the MMP enclosure, in accordance with the
NEC/CEC you must determine your equipment-grounding conductors based on the ampere rating
of the overcurrent device protecting the circuit conductors. Use Table 2-7 to help determine the
equipment-grounding conductor. If the circuit conductors are oversized to compensate for voltage
drop, the equipment-grounding conductor must also be oversized proportionally.
Table 2-7, Equipment Grounding Conductor Sizing
Rating of Overcurrent
Device
Minimum Size of Copper
Ground Wire
15 amp #14 AWG
20 amp #12 AWG
30-60 amp #10 AWG
100 amp #8 AWG
200 amp #6 AWG
300 amp #4 AWG
400 amp #3 AWG
2.10.3 System Bonding Jumper
The MMP enclosure provides the single point of ground [System Bonding Jumper (SBJ)] for the
AC and DC system. If the MMP enclosure is the central connection point for all ground wiring
(usually in an off-grid system) and there is no other connection from AC neutral or DC negative
to ground in the AC or DC system, then leave the ground bond connections in place. Remove any
other neutral-ground connection in the AC system, such as in other electrical sub-panels; or, any
negative-ground connection in the DC system.
For utility connected systems where the neutral and ground are already bonded in the main utility
circuit breaker box (AC distribution panel), the GREEN GROUND/NEUTRAL bonding wire MUST BE
REMOVED from the MMP enclosure. See Section 2.11 to remove this neutral-ground connection.
Info: Inverters and portable generators that have electrical outlets usually have the
neutral and ground bonded internally. These types of devices are not recommended to
be connected to the MMP/inverter system as they would fi rst need to be modi fi ed to
separate the neutral and ground bonding internally.
For systems or devices that connect the DC negative to ground independently (i.e., separate
DC main electrical distribution panel or PV-GFP device), the Negative to Ground busbar (Item 1,
Figure 1-2 or 1-4) MUST BE REMOVED inside the MMP enclosure. See Section 2.12 to remove this
negative-ground connection.