Backfeed Protection
 DANGER |
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Hazard of electric shock, explosion, or arc flash
In systems where backfeed protection is not part of the
standard design, an automatic isolation device (backfeed protection
option or other device meeting the requirements of IEC/EN 62040–1)
must be installed to prevent hazardous voltage or energy at the input
terminals of the isolation device. The device must open within 15
seconds after the upstream power supply fails and must be rated according
to the specifications.
Failure to follow these instructions will result in death or serious injury.
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When the UPS input is connected through external isolators that, when opened, isolate the neutral or when the automatic backfeed isolation is provided external to the equipment or is connected to an IT power distribution system, a label must be fitted at the UPS input terminals, and on all primary power isolators installed remote from the UPS area and on external access points between such isolators and the UPS, by the user, displaying the following text (or equivalent in a language which is acceptable in the country in which the UPS system is installed):
| DANGER |
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Hazard of electric shock, explosion, or arc flash
Risk of Voltage Backfeed. Before working on this circuit:
Isolate the UPS and check for hazardous voltage between all terminals
including the protective earth.
Failure to follow these instructions will result in death or serious injury.
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An additional external isolation device must be installed in the UPS system. A contactor can be used for this purpose. In the shown examples, the isolation device is a contactor (marked with a MC1 for single mains systems and marked with a MC1 and MC2 for dual mains systems).
The isolation device must be able to withstand the electrical characteristics as described in the input specifications.
Single Mains UPS and External Isolation Device
Single Mains UPS with Backfeed Box
Dual Mains UPS and External Isolation Device
Dual Mains UPS with Backfeed Box
