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Quizzes on the Code

Oct 1, 1998 12:00 PM, By Fred Hartwell, Senior Editor

Give the best answer:

1. Assume the total size of the load is appropriate, and the transfer switch feeds a single fused switch ahead of a panelboard. If a hospital below 150kVA in total essential system load has just one such transfer switch, which loads can be connected to that panelboard?

1. Surgical compressed air systems

2. Elevator cab lighting

3. Nurse call systems

4. Two of the above

5. All of the above

2. Which of the following locations/methods could support a feeder to a remote panelboard supplying emergency lighting in a high-rise hotel?

1. EMT with structural beam spray

2. Rigid metal conduit in a 2-hr-rated chase

3. EMT above a suspended ceiling with full-coverage sprinklers for the rooms below

4. d. None of the above

5. e. More than one of the above

3. Which of the following is true concerning unit equipment used as a source of emergency illumination in a typical hallway?

1. Equipment must be hard wired.

2. The circuit feeding it must be specifically identified as such in the panelboard circuit directory.

3. It must always be supplied by a local branch circuit that supplies loads such as receptacles in that hallway.

4. Two of the above

4. A local regulation requires the lift pumps at a sewage treatment plant have standby power. Any outage would be a critical, particularly during peak flow periods. Which requirements must be adhered to on this system?

1. Branch circuits to the pumps must not run in the same raceways with non-critical loads.

2. The system must connect to standby power if the event of an outage within 10 sec.

3. The feeder must have sprinkler protection or be an electrical circuit protective assembly.

4. Two of the above

5. None of the above

5. Emergency systems must always be suitable for their intended function. Which of the following would not be a code requirement to assure this capability on a large 480Y/277V system with a 1600A main disconnect?

1. The AHJ must conduct or witness periodic system tests.

2. Automatic ground-fault protection must be provided so the system won’t create its own hazard.

3. Use system for emergencies only.

4. The equipment must be suitable for the maximum fault current available at its terminals.

Answers and Discussion

1. d, Sec. 700-9(a) Ex. 1. Emergency system transfer switches are only permitted to supply emergency load. The compressed-air system in response “a” is on the equipment system of the hospital, which although part of the essential system, is not part of the emergency system. The other loads, being part of the life safety and critical branches, are emergency system loads.

2. d, Sec. 700-9(c). As presently written, the sprinkler has to protect the actual feeder and not just the occupied space of the building, and no external construction method creates an electrical circuit protective system. Beam sprays have been commonly seen in an attempt to comply with these rules after the completion of installation. They’re relatively inexpensive, and they don’t work. They’re designed to prevent steel structural members from softening, which occurs at about 1000°F to 1200°F. At those temperatures, an electrical circuit will survive only a matter of seconds, not hours.

3. b, Sec. 700-12(e). Flexible cord can be used, provided it isn’t over 3 ft in length, and remains permanently fixed in place. The branch circuit supplying it must be so identified. This makes it more obvious if the equipment is improperly connected to a local receptacle circuit, for example. It has to go on the local lighting circuit, ahead of local switching.

4. e, Sec. 701-10, 701-11. This question describes a legally required standby system, not an emergency system, and the minimum time for connection is extended from 10 sec. to 60 sec. Note that this is conditional on 60 sec. being “within the time required for the application.” If a shorter time were required, then that restraint would have to be met. Legally required standby system circuits may run in the same enclosures with other circuits. The new rule in Sec. 700-9(c) for enhanced protection of emergency systems in large buildings doesn’t apply in Art. 701. Furthermore, the treatment plant wouldn’t be likely to meet the size or height requirements to invoke that rule, even if these circuits were emergency in character.

5. c. Sec. 700-5(b). The use of an emergency system for other purposes, such as load shedding, is allowable— provided automatic controls assure that when the system is called upon for emergency circuits, the other loads are disconnected as required to allow the emergency loads to function as intended. The testing is required in Sec. 700-4(a) and (b), and the fault duty is required by Sec. 700-5(a). Although Sec. 700-7(d) requires an alarm for a ground-fault condition which would otherwise initiate a system trip for conventional feeders and services, in this case the alarm can be substituted, per Sec. 700-26.

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