MidNite Solar MNDC125 User manual

14000 Burn Rd
Arlington, WA 98223
USA
Ph [phone]
www.midnitesolar.com
MNDC Instructions
Rev: New Page 1 of 7
Model: MNDC125, MNDC175, MNDC250
Shown with 250 amp sized breaker MNDC closed
The Mini-DC was designed to take into account many different types of renewable energy
installations. These installation instructions will describe and show some of the more common
possibilities.
Features:
•Aluminum chassis. (no rust in the tropics or around salt water)
•Hinged door for easy access to electrical circuits
•Inverter breaker included (125, 175 or 250 amp)
•Din rail for DC circuits such as PV in, Chg Cntrl out, DC-GFP, DC loads, PV combiner
•Ground bus bar with 14 poles
•Six mounting spots for 500 amp, 50mV shunt
•Mounting spot for insulated bus bar (for PV negative connection point)
•Knock outs for inverter and battery cables, charge control mounting, DC & PV in & out
•5/16” diameter stud for battery negative tie point

MNDC Installation Instructions
Rev: New Page 2 of 7
Dimensioned drawing showing conduit locations and sizes
Wire type
Due to the small size of this box and limited wire bending room, it is required that the super
flexible type battery cable be utilized. Cobra Cable X-Flex is one approved type of cable.
Welding cable although not listed for use in residential wiring will also meet the flexibility
requirement. Wiring for the din rail mount breakers such as 6AWG for PV circuits may be the
stiff THHN or similar type of wire.
Top view showing three 1” knockouts. The left
two knockouts fit charge controllers such as the
Classic, MX60, C-40 and Tristar controllers
The left side of the
MNDC chassis has
three 2” knockouts
and two ½”
knockouts. The 2”
knockouts are
intended for inverter
DC cables. If
installing to a Trace
or Xantrex SW
inverter, use a 2”
offset nipple to
attach to the SWCB
conduit box.
If routing cables
directly through the
hole with no
conduit, make sure a
plastic grommet is
installed to avoid
chafin
g
.
The bottom surface is normally where the
battery cables will enter. The 1” knockout can be
increased in size to accommodate a second 2”
conduit opening if required. This is one way to
hook up to a Trace or Xantrex DR Series conduit
b
ox.

MNDC Installation Instructions
Rev: New Page 3 of 7
Wiring diagram supplied on the door of MNDC
Grounding
There are various ground circuits that need to be considered in the renewable energy system. The
MNDC chassis should be grounded to your earth ground rod through a 6AWG wire connected to
the ground bus bar located in the top left section of the MNDC chassis. The MNDC ground bus
bar will then become your primary system DC ground. The ground bus bar is also where DC
lightning arrestors get grounded. It is advisable to use one of the ½” conduit knockouts to mount
a DC lightning arrestor to the MNDC box. It is also common to have a DC lightning arrestor out
at the PV Panels that are grounded through their own ground rod. In dry climates it is advisable
to also run a ground wire from the PV panels to the MNDC ground. The MNDC ground bus bar
is an ideal place to ground a DC-GFP when installed as well as the inverter chassis and the
charge control chassis. Do the grounds first since they normally lie in the bottom of the chassis.
Ground Bus Bar

MNDC Installation Instructions
Rev: New Page 4 of 7
Battery Negative connection
The wiring diagram shows a 500 amp shunt. This is used to measure voltage drop across the
shunt to aid in calculating battery state of charge. The shunt does not ground the battery negative
circuit. If this shunt is not installed, then you may use the 5/16” stud directly above the shunt
area as a battery negative tie point. Using this tie point will ground the battery negative to the
chassis. Grounding the battery negative is not allowed when employing a DC-GFP device. The
inverter side of the shunt or the 5/16” stud are also an ideal tie point for PV negative or other DC
negative circuits.
Battery status monitor systems such as the Trimetric, E-Meter, Trace Meter etc are available with
or without the 500 amp 50mV shunt. The MNDC does not come with this shunt, so you will
need to order the shunt.
Shunt mounted horizontal on bottom dimples Shunt mounted vertical on bottom dimples
5/16” stud for battery negative tie point
Battery Positive connections
DC positive from the battery bank connects to the lower section of the large DC inverter breaker.
The lower inverter breaker stud is also the common point for connection of additional DC
circuits such as from the output of a charge controller. Do not connect other charging sources to
the top of the inverter breaker as this would apply power to the inverter even when the inverter
breaker is turned off. The top section of the inverter breaker connects to the inverter positive
battery terminal post. The following photo shows the inverter breaker wired with an additional
charging source connected to the bottom section of the breaker.
The hardware kit bag contains a 5/16”
kepnut for use with this grounding battery
negative stud.

MNDC Installation Instructions
Rev: New Page 5 of 7
Battery Positive connections and shunt wiring
Wire exit to inverter
Din Rail mounted breakers
There are three 2” conduit
knock outs for inverter wire
exit. Carefully analyze the
possible wire exit paths to
the inverter. Six different
shunt placement options
have been provided in order
to better accommodate a
wide range of inverter
options. Cables may also
exit the bottom in order to
reach an inverter not
mounted to the left of the
MNDC enclosure.
Note the 6AWG wire
connected to the lower
section of the inverter
battery breaker. This
comes from the output
breaker from a charge
controller.
The inverter negative
shunt connection has the
corresponding negative
circuit from the charge
controller and negative
from the DC-GFP.
Din Rail mount breakers
shown are for a solar charge
controller and a DC-GFP.
PV in is entering the MNDC
from the bottom in this photo.

MNDC Installation Instructions
Rev: New Page 6 of 7
DC Breakers and Cover
MNDC uses for various different inverter installations.
Remove the DC
breaker cover to install
din rail mount
breakers. Insure the
yellow tab snaps into
place to secure the
breakers. Strip wires
3/8” and bend at ¾”
from end. This section
is very tight so pay
close attention to wire
routing. Use cable ties
to secure wires in a
neatly routed bundle.
Lat the cover plate on
a flat scrap wood
surface and using a
flat screw driver blade
and hammer, cut the
tabs.

MNDC Installation Instructions
Rev: New Page 7 of 7
MNDC fully wired