EDCO TECHNICAL BULLETIN 10390

ISOLATED LOOP CIRCUIT PROTECTORS


Configuration Selection

The COHP SERIES surge protectors can be ordered in two basic configurations. The COHP (FS), failsafe products are designed for both PRIMARY PROTECTOR (UL497) and ISOLATED LOOP CIRCUIT PROTECTOR (UL497B) applications, The COHP products, without failsafe, are intended only for UL497B applications. These requirements state that the circuit is isolated both from (1) direct metallic connection to the telephone network, and (2) from exposure to high voltage power cross. This will be explained in detail later.

Voltage Selection

The COHP SERIES surge protectors are available in four standard voltage ratings. To properly select a COHP for a given application, one must FIRST know the maximum peak operational voltage on the pairs to be protected. Next, ADD four volts to that number, and then SELECT the COHP with a voltage suffix equal to or higher than the calculated number. An example: We deterrmine that the maximum peak operational voltage is 24 volts. Then, adding four to that number yields a selection voltage minimum of 28 volts. The proper COHP would be either a COHP-030 or COHP-030FS.

Dual Listing

As you have observed, the COHP (FS) SERIES surge protectors have a dual UL listing. This enhances the flexibility and cost economy available to the user. Site-related parameters called out in Article 800-30 of the NEC (National Electrical Code) govern whether the protectors are to be installed as PRIMARY PROTECTORS (UL497) or as ISOLATED LOOP CIRCUIT PROTECTORS (UL497B). This section of the code is printed herein for your convenience. Also examples of both types of installations are shown.

INSTALLATION INSTRUCTIONS

1. Protocols must be keyed properly on the 66 block. This is accomplished during initial installation by placing the grounding bar (MGB) on the OUTSIDE PLANT (unprotected) side of the 66 block.

Position the MGB parallel to the outside plant side of the M block.

2. Insert end hook around outside fanning strip of M block and gently pull into place, aligning angle brace as shown in Fig. 1.

3. Using mounting hardware provided, attach other end of MGB to M block mounting tab.

4. Tighten mounting screw once MGB is aligned parallel to M Block.

5. Connect ground wire to ground lug. Use at least a #10 gauge wire. Bond protection ground according to recognized procedures.

6. Simply plug in the COHP module on M block and MGB. The module replaces the T & R bridging clips. It is suggested to line up the ground rail connector clip first.

National Electric Code Wording


800-30. Protective Devices

(a) Application. A listed protector shall be provided on each circuit run partly or entirely in aerial wire or aerial cable not confined within a block. Also, a listed protector shall be provided on each circuit, aerial or underground, so located within the block containing the building served as to be exposed to accidental contact with electric light or power conductors operating at over 300 volts to ground. Installation of protectors shall also comply with Section 110-3 (b).

(FPN No. I): The word "block" as used in this article means a square or portion of a city, town, or village enclosed by streets and including alleys so enclosed but not any street.

(FPN No.2): The word "exposed" as used in this article means that the circuit is in such a position that, in case of failure of supports or insulation, contact with another circuit may result.

(FPN No.3): On a circuit not exposed to accidental contact with power conductons, providing a listed protector in accordance with this article will help protect against other hazards such as lightning and above-normal voltages induced by fault currents on power circuits in proximity to the communications circuit. When protecting a circuit run within the block between two buildings on the same premises, providing a listed protector on each cod of the circuit affords protection for both buildings.

SPECIFIC INSTRUCTIONS FOR UL-COMPLIANT LOOP CIRCUIT PROTECTOR INSTALLATION

Either COHP SERIES or COHP (FS) SERIES protectors can be installed as shown in Figures 2, 3 and be compliant with UL497B if requirements in Article 800.30 of the NEC are met at the site. The basic requirement in the NEC code is that accidental exposure to continuous voltages in excess of 300 volts to ground be eliminated and that the cable plant be entirely located on the property (campus) without crossing any public street or alleyway (within the same block). In addition, no direct metallic connection can exist between said cable pairs and the telephone network. Extension pairs originating at local CPE can be considered an ISOLATED LOOP CIRCUIT if it is within the block described above.



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