COHP (FS) Primary Protectors (UL 497)


Configuration Selection

The COHP (FS) SERIES protectors have a dual UL listing. This enhances the flexibility and cost economy available to the user. Site-related paranieters 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. This instructional booklet describes PRIMARY PROTECTOR (UL497) installation only.  Refer to TB 13090 for installation as an ISOLATED LOOP CIRCUIT PROTECTOR (UL497B).

Voltage Selection

The COHP (FS) SERIES 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 sulfix equal to or higher than the calculated number. An example: we determine 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 a COHP-O3OFS as a PRIMARY PROTECTOR.

Basic Requirements

*For Effective Protection

1. Protectors 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 block.

2. A local (at protected equipment) single point ground must be established. This is illustrated later in detail.

*Protectors are installed in place of bridging clips on a standard split 66M1 -50 block. One ground rail (MGB) is required for each

*Never install telephone wiring during a lightning storm.

*When used as PRIMARY PROTECTORS: protectors must be installed in a UL recognized housing in order to be considered a UL-Compliant installation.



1. 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

3. Using mounting hardwdare 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. Thc module replaces the T & R bridging clips. It is suggested to line up the ground rail connector clip first.

National Electric Code Wording


a) Application. A UL 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 I 10-3 (b).

(PPN 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 conductors, 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 end of the circuit affords protection for both buildings.


Mounting and Housing

For use as a UL-compliant primary protector, a mounting and housing arrangement described below is mandatory. The protectors must be mounted on a UL recognized 66 type block (ref: Siemon S66M1-50) inside a UL recognized enclosure (ref: Square'D type 12124B or equal) for indoor or outdoor use. Note that two 66 blocks are used for each group of 25 cable pairs so that the required fusible wire link can be installed between the blocks as shown in Figure 2. INPUT cable using 22 or 24 AWG solid conductors, which meet local code requirements, and OUTPUT cable using 24 AWG solid conductors, also meeting local code requirements must be used as cabling termination to box. INPUT cable is that which enters from outside building. OUTPUT cable is that between protector box and protected equipment. If the INPUT wire size is 22 AWG, then 24 or 26 AWG solid copper wire with thermoplastic insulation may be used as the fusible wire link. If the INPUT wire size is 24 AWG, then 26 AWG copper wire (ref: Belden #9976) with thermoplastic insulation must be used as the fusible link. UL recognized bushings (ref: Heyco #2119) must be used at the two cable entry and exit holes in the protector enclosure.

Grounding Requirements

The INPUT cable sheath and the MGB grounding bar lug must be connected to a ground wire (6 AWG preferred) and run to the single point ground referenced in Figure 3. Grounding wires should not be run in metal conduits.



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