Advanced Protection XRL - Manual (Page 5)

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and ensure that nearest breaker positions are used. If new
construction, adjust breaker locations as appropriate.
Tip: Voltage drops for normal 120V or 277V lines might be 2-3V
per hundred feet. In surge applications, voltage drops might
be 100-150V per foot. These voltage drops add to clamping
voltage, thus hurting performance. Make every effort to keep
leads short and straight.
As distribution gear becomes larger, shorter leads are more
difficult to accomplish. When longer leads are unavoidable,
gently twist leads together (one to two twists per foot), or
tie-wrap leads together.
Tip: surges create magnetic fields per the ‘right-hand rule’.
When current goes in direction of thumb, magnetic field is
in direction of curl of fingers. As surge current goes to SPD,
fields are created in one direction. When the SPD sends those
currents to neutral and/or ground, current goes in the opposite
direction. If ‘coming & going’ are on the same axis, the magnetic
fields can be cancelled, thus avoiding performance decrease.
Gentle twists, bundling & tie-wraps accomplish this.
Shortest Leads Possible
▪
Leads must be as short and straight as possible -
See NEC ® Art. 285.12
▪
Pretend wire is $1000 per foot coming out of your pocket.
▪
No long leads
▪
No sharp bends
▪
No wire nuts
▪
How short is short enough? As short as you can make it.
▪
How long is too long? If anyone else can make it shorter.
Overcurrent Protection
SPDs draw very little current under normal conditions and
conduct for a brief duration upon encountering a transient
surge current. This SPD contains internal overcurrent and
overtemperature protection to protect against abnormal
voltage conditions.
Supplemental overcurrent protection is not required to protect
this SPD. However, connecting conductors require protection
in Type 2 or 4 applications. Follow applicable codes.
Voltage Rating
Before installing SPD, verify that it has the same voltage
rating as the power distribution system. Compare the SPDs
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.
Circuit Breaker and Disconnect Switch
The XA & XB family SPDs are tested and qualified as a Type
1 SPD per UL 1449 Third Edition and 2008 NEC ® . This SPD
can be installed on the line side of the service overcurrent
device per 2008 NEC ® 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 60A circuit breaker. The circuit breaker is
the intended disconnect switch and provides short circuit
protection to the connecting conductors. These SPDs have
internal overload protection elements within the product. A
breaker or disconnect is not required for the SPDs overcurrent
protection. These SPDs have demonstrated 200kA Short
Circuit Current Ratings (SCCRs). 120V & 120/240V models
have demonstrated 100kA SCCRs. Refer to label on unit.
Terminals
Terminals will accept 14 - 2 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 6
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, large conductor
tends to have the same inductance as smaller conductor,
thus netting limited improvement in exchange for being more
difficult to work with. Terminals accept 14 - 2 AWG conductor
with 6 AWG being preferred. Coordinate conductor size and
overcurrent protection per applicable codes.
If equipped, Disconnect Switch will accept 6 AWG to 1/0
AWG, with 6 AWG preferred. Torque connections to 18
inch-pounds. Do Not overtorque connections on Disconnect
Switch as it Will Break the Disconnect Switch and will not
be covered by warranty.
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).