hb719 bypass schematic - 3 position

This set of pictures shows the functional arrangement of Advance 3 position bypass switches as used with UPS systems

The bypass switch must be correctly sized in terms of current capacity (Amps) for the UPS 

Installers should be aware that the bypass must be installed in compliance with all relevant codes.

The input, UPS and output EARTH connections to the switch must ALL be made and tested for continuity

In normal use the switch is switched to `NORMAL' which provides the critical load with UPS protection. When the UPS is to be tested, the critical load is operated from the main supply via the bypass switch in the `TEST' position. When the UPS is to be disconnected, the switch is put in the `BYPASS' position

switch position




supply to UPS input and UPS supplies output

supply load

UPS & BYPASS (older units TEST)

supply to UPS input  and supply to load

supply load


supply to load via switch UPS isolated

supply load

Switch type

Switched connections

Single phase 

Live and neutral

Three phase

L1,L2,L3 and neutral

These notes are provided to assist trained electricians in the principle of operation and are not intended for use by unskilled personnel

part of the AEL technical handbook return to hb000 Handbook Index