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standards and guidelines for communication sites - Radio And ...

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AC POWER SPD REQUIREMENTS CHAPTER 7: SURGE PROTECTIVE DEVICES<br />

To Alarms Panel<br />

(Recommended)<br />

Equipment room or area.<br />

SPD<br />

(Surge Suppressor)<br />

Type 1 SAD/MOV<br />

To Alarms Panel<br />

Electrical meter <strong>and</strong><br />

disconnect are located<br />

outside the equipment<br />

room or area within<br />

another structure.<br />

UPS<br />

Utility<br />

Panelboard<br />

with a main<br />

breaker<br />

Step Down or<br />

Isolation<br />

Trans<strong>for</strong>mer<br />

Circuit<br />

Breaker<br />

Main Disconnect<br />

Switchgear or<br />

Distribution<br />

Panelboard<br />

Type 3 SPD<br />

optional<br />

Meter<br />

FIGURE 7-9 SPD INTERCONNECT BLOCK DIAGRAM ‘H’<br />

NOTES: 1. The main service disconnect is located outside the equipment room or area within another structure.<br />

2. The service to the equipment room or area is 3 conductors with ground <strong>for</strong> single phase or 4<br />

conductors with ground <strong>for</strong> 3 phase.<br />

3. The step-down or isolation trans<strong>for</strong>mer creates a separately derived system where the neutral <strong>and</strong> ground conductors are<br />

bonded together within the trans<strong>for</strong>mer <strong>and</strong> bonded to the equipment room MGB. The main disconnect ground <strong>and</strong> the MGB<br />

shall be bonded to the site grounding electrode system at the same point.<br />

4. The Utility panelboard shall use a main disconnecting device to serve the equipment area.<br />

5. The Type 1 SPD shall be installed per the manufacturer’s installation instructions.<br />

6. All conductors between the SPD <strong>and</strong> the associated disconnecting device shall be as short as possible <strong>and</strong> routed<br />

together with a minimal number of bends or angles of less than 90 degrees.<br />

7. The SPD disconnecting device should be installed in the topmost space available in the Utility Panelboard.<br />

8. Installation of Type 3 SPDs on each critical load is recommended where the level of exposure is high.<br />

9. Installation of Type 3 SPDs on each non-critical load that is located greater than 3 m (10 ft.) of conductor length from the<br />

panelboard is recommended where the level of exposure is high.<br />

7-18 68P81089E50-B 9/1/05<br />

UPS<br />

Panelboard<br />

Non-Critical<br />

Loads<br />

Type 3 SPD optional<br />

when greater than<br />

10 conductor feet<br />

from panelboard.<br />

Critical<br />

Loads<br />

Utility Feed<br />

AC<br />

240/120 Single Phase<br />

208/120 3 Phase<br />

480/277 3 Phase

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