Advanced Protection TWL - Manual (Page 6)

• Presumed indoor use: If outdoor, need appropriately sized outdoor rated enclosure to house TWL and all SPDs.
• Anticipate wiring and conduit into and out of TWL
• AC Power – Intended to come from upstream service entrance SPD, enter TWL hub, connect to TWL-housed AC power
SPD, and conductors exit TWL to Tower Light Controller.
• Photocell – Intended for lead from photocell to enter Unprotected side of DIN Rail mounted SPD. This is a series SPD.
The load travels through this SPD, which is different than the other SPDs, which are parallel-connected. This SPD is
‘directional’. If the Unprotected and Protected ends are miss-connected, the SPD will provide decreased surge protection.
Direction is important!
• Uptower loads: Leads are intended to enter the TWL at the bottom, connect to appropriate SPDs within the TWL, then
the leads exit at the top of the TWL to uptower. Other orientations are possible depending on situation. For example, the
TWL can be mounted sideways if required. The proposed APT SPDs are not direction or orientation sensitive.
• Anticipate ground conductor path to ground grid or ground. Intended to use 4” copper ground strap to connect to existing
grounding grid. This path needs to be straight, no bends or kinks.
• It is physically possible to use large gauge ground wires. However, traditional round wire has much more inductance than
flat strap. This hurts performance in surge & lightning protection scenarios. Given a choice, using round wire would be a
mistake. If round wire is unavoidable, we recommend multiple, exactly-parallel ground wires of equal length to minimize
inductive losses.
3. Mount TWL to Wall
• Consider mounting the 4” copper ground strap to an appropriate location on the backside of the TWL before mounting
the TWL to the wall. This may be easier, see #4 below.
• Mount TWL to wall using the four attachment holes on the aluminum baseplate. Use appropriate attachment hardware
(not included).
• Ensure that 4” copper ground strap is installed and robustly connected to ground system. Failure to provide reliable
ground will defeat the purpose of the TWL and associated SPDs.
4. Connect 4” copper ground strap to TWL (Figure 2)
Four sets of predrilled holes are provided; one on each side of the TWL. This maximizes effectiveness, eases installation,
and also allows bonding to other equipment if desired. If required, these can be used to bond two TWL’s side by side.
The 4” copper ground strap is intended for installation directly under the aluminum backplane with robust bolts (included).
The aluminum backplane is tin-plated to prevent dissimilar metal cathodic interaction (prevent corrosion).
The backplane is elevated approximately 7/8” to provide working access. Torque connections to 7 lb-ft. Ensure that ground
strap is not ripped or torn during installation.
5. Run wire bundles into TWL, MARKING ALL conductors
• Use appropriate care to separate wires into separate conduit(s). Use appropriate conduit and connectors to the TWL.
• It may be appropriate to provide separate conduit(s) for AC power and/or the photocell (if equipped).
6. Connect individual SPDs
• We suggest installing SPDs in the following order:
- 1. Photocell – do this first to get it out of the way
- 2. Individual light SPD(s) (there may be several)
- 3. AC power SPD – do this last because it will cover the work area making work on other units more difficult
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