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Parallel Connection
When making a parallel type of connection (Figure 1), the length of the wiring to the Surge Protection Device (SPD)
must be kept as short as possible to substantially enhance the performance. Long wire runs are to be avoided if the
unit is to perform as intended.
To reduce the impedance the wire displays to surge currents, the phase, neutral (if used), and ground conductors are to
be routed within the same conduit and should be tightly bundled or twisted together to optimize performance of the
unit. Sharp bends in the conductors are to be avoided.
Wire Size
With a parallel connection, the size of the wiring to the SPD is independent of the ampere rating of the circuit to be
protected. The recommended wire size is based on the unit’s transient surge current capabilities. #6 AWG is the rec-
ommended wire size for phase, neutral, and ground.
**Surge Protection Devices are designed for use on the load side
of the service entrance disconnect only**
Typical Unit Installation - Three Phase WYE, 4 Wire, plus Ground
This section provides basic installation instructions for the PM3 and PM4 SPDs. Per UL 1449 Paragraph 1.4, SPDs
"are intended for installation on the load side of the main overcurrent protection". Locate the SPD as close as possible
to the circuit to be protected to minimize the wire length. This will optimize SPD performance.
Note that these instructions are not intended to supercede local or national codes. The installation should be per-
formed by a licensed electrician. To install a PM3 or PM4 SPD, refer to Figure 2 and proceed as follows:
1. Unpack and inspect the unit for signs of damage. If the unit is damaged, contact APC Customer Service (see Page
17 for the APC Customer Service phone number, as well as obtaining service under the Warranty.
2. Locate where the unit is to be installed. Ensure wire lengths between the SPD and the service panel are kept to a
minimum.
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Interconnecting Wiring
* Minimize Length
* Avoid Sharp Bends