Automatic Transfer Switches
Cross-references point to the standards that now own the topic after the October electrical rewrites: MV cable to medium-voltage-cables, energy storage to battery-energy-storage-systems, service grounding to grounding-and-bonding, lightning to lightning-protection.
Showing changes from Rev 8
to Rev 9
in Automatic Transfer Switches.
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title: Automatic Transfer Switches
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When to use: Automatic transfer switches rated 1000 V and below, listed to UL 1008, that move a load between a normal source and an alternate source without operator action. Covers the switching mechanism, transition type, bypass-isolation construction, neutral treatment, the controller and its sensing, time delays, exerciser, load management and communications provisions, ratings including withstand and closing and short-time ratings, service-entrance construction, enclosures, identification, factory and field testing, installation, warranty, and spare parts, for switches serving emergency, legally required standby, optional standby, critical operations, and health care essential electrical system loads.
− Not intended for: The system-level design of the emergency and standby power system, including load classification, source selection, transfer scheme, and selective coordination ([[sync/emergency-and-standby-power]]); the engine-generator set and its controls ([[sync/generators]]); the branch topology of a health care essential electrical system ([[sync/healthcare-essential-electrical-systems]]); manual and non-automatic transfer switches; medium-voltage transfer switches and source-transfer schemes above 1000 V; static transfer switches and the transfer of a UPS between its bypass and inverter ([[sync/uninterruptible-power-supply-systems]]); paralleling switchgear with more than one generator on a common bus; and utility-owned switching at the service point.
+ Not intended for: The system-level design of the emergency and standby power system, including load classification, source selection, transfer scheme, and selective coordination ([[sync/emergency-and-standby-power]]); the engine-generator set and its controls ([[sync/generators]]); the branch topology of a health care essential electrical system ([[sync/healthcare-essential-electrical-systems]]); manual and non-automatic transfer switches; medium-voltage transfer switches and source-transfer schemes above 1000 V; static transfer switches and the transfer of a UPS between its bypass and inverter ([[sync/uninterruptible-power-supply-systems]]); paralleling switchgear with more than one generator on a common bus ([[sync/generator-paralleling-switchgear]]); and utility-owned switching at the service point.
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- the short-circuit, coordination, and arc-flash studies that establish the ratings and settings the switch is ordered to ([[sync/short-circuit-study]], [[sync/protective-coordination-study]], [[sync/arc-flash-study]])
- the room the switch occupies ([[sync/electrical-rooms]]) and the concrete pad as a structure ([[sync/concrete-pads]])
−- manual and non-automatic transfer switches, medium-voltage transfer schemes, static transfer switches, and paralleling switchgear
+- manual and non-automatic transfer switches, medium-voltage transfer schemes, static transfer switches, and paralleling switchgear ([[sync/generator-paralleling-switchgear]])
## The location of each transfer switch shall be as indicated on [[drawing: the electrical plans]].
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### The system bonding jumper and grounding electrode connection of the alternate source shall be installed, or omitted, in accordance with the neutral treatment selected under this standard, and the Contractor shall record the as-installed condition on the as-built one-line diagram.
−### Where the switch is service equipment, the grounded conductor and the grounding electrode connections shall comply with NEC 250.24 and [[sync/electrical-service-entrance]].
+### Where the switch is service equipment, the grounded conductor and the grounding electrode connections shall comply with NEC 250.24 and [[sync/grounding-and-bonding]].
## Wiring Separation {toc}
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constraint: min
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