Advanced Protection XDS - Manual (Page 4)

Article 285. As a generalization, it is more practical
to install on load side of main overcurrent device
for maintenance reasons.
When connected on load side of main disconnect,
we suggest connecting via a 50-30A circuit
breaker. The circuit breaker is the intended
disconnect switch and provides short circuit
protection to the connecting conductors. The XD
Series has internal overload protection elements
within the product. A breaker or disconnect is not
required for the SPDs overcurrent protection. XD
SPDs have demonstrated 200kA Short Circuit
Current Ratings (SCCR). 120V and 120/240V
XDs have demonstrated 100kA SCCRs. Confer
to label on unit.
Terminals
Terminals will accept 14 - 8 AWG conductor and
are provided for line (phase), neutral (if used),
and equipment safety ground connections.
8 AWG is the minimum recommended wire
size because UL testing and evaluation was
performed using 8 AWG.
Wire Size and Installation Torque
This is a parallel-connected SPD; it is not
series-connected. The size of the SPD wiring is
independent of the ampere rating of the protected
circuit. Recommended wire is 8 AWG for
phase, neutral and ground connections. Torque
connections to 18 inch-pounds. Conductor length
should be as short as possible.
If other wire sizes are used, we recommend that
all conductors be the same gauge. Note that
larger conductor might appear to be beneficial;
however, it tends to have the same inductance
as smaller conductor and is more difficult to work
with. Terminals accept 14 - 8 AWG conductor with
8 AWG being preferred. Coordinate conductor size
and overcurrent protection per applicable codes.
System Grounding
An equipment grounding conductor must be used
on all electrical circuits connected to the SPD.
For the best performance, use a single point
ground system where the service entrance
grounding electrode system is connected to
and bonded to all other available electrodes,
building steel, metal water pipes, driven rods, etc.
(for reference see: IEEE Std 142-2007).
For sensitive electronics and computer systems,
we recommend that the ground impedance
measurement be as low as possible. When
metallic raceway is used as an additional
grounding conductor, an insulated grounding
conductor should be run inside the raceway and
sized per the NEC ® . Adequate electrical continuity
must be maintained at all raceway connections.
Do not use isolating bushings to interrupt a
metallic raceway run.
A separate isolated ground for the SPD is NOT
recommended. Proper equipment connections
to grounding system and ground grid continuity
should be verified via inspections and testing
on a regular basis as part of a comprehensive
electrical maintenance program.
On 4-Wire Power Systems, neutral to ground
bonding (Main Bonding Jumper) must be installed
per the NEC ® . Failure to do so WILL damage SPDs.
Voltage Rating
Before installing SPD, verify that it has the same
voltage rating as the power distribution system.
Compare the SPD’s nameplate voltage or model
number and ensure that SPD configuration
matches the intended power source. See Table 1.
The specifier or the user of the device should be
familiar with the configuration and arrangement of
the power distribution system in which any SPD
is to be installed. The system configuration of
any power distribution system is based strictly on
how the secondary windings of the transformer
supplying the service entrance main or load are
configured. This includes whether or not the
transformer windings are referenced to earth via a
grounding conductor. The system configuration is
not based on how any specific load or equipment
is connected to a particular power distribution
system.
480V System Example: SPDs should be installed
per the electrical system, not per a load or motor’s
wiring connection. For example, a 480V three
phase motor might appear to be connected as a
480V Delta. In actuality, the serving distribution
system might be a 480Y/277V grounded Wye,
with or without a neutral pulled to the motor or
MCC. The system is still a 480Y/277V Wye,
even though the load is connected as a Delta.
A grounded Wye has a defined reference to
ground (i.e., neutral is bonded to ground).
Some Delta systems are ungrounded, which
have no reference to ground and are known to
become unstable in certain situations. Such
instability can cause line to ground voltage
fluctuations that may prematurely fail SPDs. For
this reason, the NEC ® Article 285 has placed
SPD restrictions on ungrounded systems. As
generalizations, SPDs for ungrounded systems
can be installed on grounded systems with a
clamping performance penalty. However, SPDs
for grounded systems installed on ungrounded
systems are almost certainly destined for
premature failure. Call APT Tech Support at
(800) 237-4567 for further information.
Dry Contact Option
One set of Form C Dry Contacts are included
with the Dry Contact option. Dry Contacts change
state during inoperative conditions, including loss
of power. Any status change can be monitored
elsewhere via Dry Contacts.