JOHNSON CONTROLS
25
Section 3 - Installation
Form 160.00-N6
Issue date: 08/27/2021
3
Figure 9 -
Motor lead connections
LD12225
Grounding
The enclosure lineup must be grounded in accordance
with the requirements of the NEC. Correct equipment
grounding must be established before making any in-
coming power connection. The enclosure sections that
are shipped separately must be connected in such a
way as to ensure a continuous grounding path, using
the ground bus located along the bottom of the enclo-
sures.
Figure 10 -
Ground bus splice connection
LD12174
Each section contains a vertical ground bus extending
from the main ground bus or ground pad to each con-
troller compartment.
Special attention must be paid to protection for operat-
ing personnel, to protection of the equipment itself, and
protection of sensitive transducers or control devices
that are electronic in nature.
The following may be used as a general guide with re-
gard to equipment grounding.
• MVVSD used as service equipment for a ground-
ed system or as a main section for separately de-
rived system.
1. The grounding electrode conductor (ground
wire) sized in accordance with NEC must be
run from the grounding electrode to the MV-
VSD ground bus or ground terminal.
2. If not already provided by the factory, a main
bonding jumper must be installed from the
incoming grounded connector bus (neutral)
to the ground bus or designated grounding
point. If a jumper is not furnished, one hav-
ing size in accordance with NEC must be se-
lected.
3. No connection must be made to ground on the
load side of any neutral disconnecting line or
any sensor used for ground fault protection.
No connections must be made between out-
going grounding connectors and the neutral.
4. In
no
case must there be a second source of
power to the MVVSD. The only source of
power must be the three-phase incoming wir-
ing to the main isolation switch
• MVVSD used as service equipment for an un-
grounded system or as a main section for a sepa-
rately derived system.
1. A grounding electrode conductor (ground
wire) sized in accordance with NEC must be
run from the controller ground bus or ground
terminal. Refer to NEC
Article 250 - Ground-
ing and Bonding
.
2. If the system is grounded at any point ahead
of the controller, the grounded conductor
must be run to the controller in accordance
with NEC
Article 250
and connected to the
ground bus or ground terminal.
At least three conduits must be run be-
tween the MVVSD and the chiller: motor
power wiring, oil pump, and control and
Modbus together, or with Modbus in a
fourth conduit.
