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04
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4. DESIGN
Microinverter technology greatly simpli
fi
es the design process compared to
conven
�
onal string inverter systems. The BD-500 allows for the PV modules to be
placed with di
ff
erent azimuths and orienta
�
ons to maximize site genera
�
on. In
addi
�
on to the layout con
fi
gura
�
on, a successful design needs to take into account
two other considera
�
ons: branch circuit sizing and voltage rise calcula
�
on.
Layout
: Since the BD-500 is a single input device. A layout map showing the
loca
�
on of each PV module and its corresponding microinverter should be
fi
rst
constructed. Care should be taken to review the DC lead length of the PV modules
to see if addi
�
onal jumpers are required to reach the DC input of the BD-500. Each
microinverter comes with a number of peelable serial number s
�c
kers. Remove a
s
�c
ker and a
�
ach them to the corresponding modules on the site map.
Branch Circuit Sizing
: Since the BD-500 uses #12 AWG cabling, NEC code speci
fi
es a
maximum breaker size of 20A. This limits the branch size to a maximum of seven
(7) devices for a 240V system and six (6) devices for a 208V system.
Voltage Rise Calcula
�
on
: The addi
�
on of daisy chained, current producing
microinverters on the AC bus results in a sequen
�
al rise in voltage along the bus,
with the highest at the furthest device. Care must be taken that the resul
�
ng
voltage doesn’t exceed the maximum permissible by code. For a 240 V system, this
is 264V and 229V for a 208V system. Please contact NEP technical support should
you need more informa
�
on on this subject.
5. PARTS NEEDED
5.1 NEP Parts
You will need the following parts from NEP:
●
Microinverters (one per every 2 modules)
●
Protec
�
ve end cap (one per branch circuit)
●
Tail cable (one per branch circuit- 16’ long)
●
Male connector (op
�
onal)
Used to make extension cables
●
BDG-256 (or BDG-256P3)
5.2 Additional Parts and Tools Required
In addi
�
on to the PV modules, racking, and associated hardware, you’ll need the
following parts:
●
MLPE rail or frame a
�
ach clamps (2 per microinverter)
• AC junc
�
on boxes (mul
�
ple op
�
ons possible)
• Cordgrip with locknut or strain relief
fi�
ng (one per branch circuit)
• A subpanel may be required for systems with mul
�
ple branch circuits
• Cable clips
• Sockets, wrenches, torque wrench, mul
�
meter, small
fl
at head screwdriver,
and mirror with extension rod
• Lightning and surge suppressor (recommended)
5.3 Lightning and Surge Suppression
Since the NEP Limited Warranty does not cover “acts of God”, such as lightning
strikes or grid irregulari
�
es, NEP strongly recommends inclusion of a surge
protec
�
on device in all systems. Lightning does not actually need to strike the
equipment or building where PV system is installedto cause damage. O
�
en, a
strike nearby will induce voltage spikes in the electrical grid that can damage
equipment. Addi
�
onally, many areas can experience irregulari
�
es in electrical
grid that can generate similar voltage spikes. While the BDM-500 includes
integrated surge protec
�
on circuitry, if the surge has su
ffici
ent energy the
protec
�
on circuitry can be exceeded and the equipment can be damaged.
Installa
�
on of a suitable surge protector signi
fi
cantly increases the protec
�
on
against such events.
5.4 Shipping Information
The BDM-500 Ships six (6) to a box with each box measuring approximately 18” x
13.5” x 16”and weighing 57 lbs. A typical pallet contains 27 boxes.
6. INSTALLATION
6.1 Pre
-
installation
Prior to installa
�
on, use the mul
�
meter to check the electrical panel to con
fi
rm
the correct service voltage per the below table. If this voltage is too high it can
prevent proper opera
�
on of the microinverters. If this is the case, the u
�li
ty
should be no
�fi
ed. However, an NEP technical representa
�
ve may be able to
adjust microinverter opera
�
onal parameters to accommodate the situa
�
on.
Residen
�
al
L1 to L2
240 Vac
Commercial
L1 to L2 to L3
208 Vac
Also, please check all microinverters and cabling for any poten
�
al damage prior
to site deployment. Remember to
fi
rst create and bring a copy of the layout
map.This map should show the physical loca
�
on of each BDM-500and their
associated PV modules in your installa
�
on.
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