Advanced Protection TWL - Manual (Page 8)

Figure 3
Page 5
PHOTOCELL SPD (FIGURE 3, 4 & 5)
• Identify an appropriate mounting location for the photocell SPD
• We suggest the less-populated area of DIN Rail opposite the intended connection of the AC voltage SPD (because there
will be more space) (Figure 3)
• Identify the SPD’s Unprotected and Protected ends. This SPD is directional. The Unprotected side needs to be wired to
the photocell. The Protected side needs to be wired to the tower light controller. Reversal will result in ineffective surge
protection. (Figure 4) Also see Alternate Installation below.
• Note that this is a series, in-line connected SPD. The signal goes through the SPD. Connection of this SPD will not
consume any of the existing feed-through terminal blocks.
• Mount the SPD on the DIN Rail
• Connect Unprotected side of SPD to photocell in appropriate conduit
• Connect Protected side of SPD to tower light controller in appropriate conduit
• Make sure SPD is properly secured to DIN Rail as that connection is the ground path for this SPD. A secondary ground
connection may be added from the SPD’s ground terminal to the aluminum backplane.
Alternate Installation (Figure 5): The APT SPD includes surge protection for two (2) different sets of conductors. If you only
have one (1) set of conductors, the SPD can be wired in a manner that provides redundant or cascade protection through
the second surge suppression path. (There is a remote possibility that the impedance of the second suppression path can
interfere with the signal. If this occurs, revert to standard installation above.)
APT DIN rail SPDs are actually two separate SPD circuits in the same package. Rather than use one circuit and abandon
the other circuit, you can use both of them in a cascade manner. This provides redundancy at no extra cost – surge goes
through the two suppression circuits within the one SPD. (This is usually a good idea for any circuit!)
There is an ‘Unprotected’ side and a ‘Protected’ side. (The ‘Unprotected’ side has the ground lug)
1.) Wire from the Photocell into either Unprotected side,
2.) Loop from one Protected side to the other Protected side,
3.) Wire to the tower light controller from the other Unprotected side.
Note schematic on SPD
Do Not reverse the Unprotected & Protected sides or you will hurt performance.
Photocell SPD can be mounted
on any open DIN rail area
Photocell SPD Mounting Location