-Bypass/Isolation Switches- Russelectric Builds Two Types: Failsafe & Maintenance

A Bypass/Isolation switch (switch within a switch)… Benefits and main purpose of a bypass/isolation switch Bypass switching section ATS switching section (mounted in a draw-out assembly) A Bypass/Isolation switch (switch within a switch)… Power can be maintained to load during ATS failure and until the ATS is repaired. Provides a means of bypassing the ATS for maintenance Unit can be operated as a manual transfer switch until the automatic portion is serviced and/or repaired

Bypass/Isolation Functions Variations on the Theme Russelectric offers the most variations, beginning with 2 major considerations: 1. Bypass feature used mainly for maintenance of the automatic transfer switch portion of the unit (Maintenance bypass) 2. Bypass feature used mainly in emergency situations (Failsafe bypass) ATS Portion of unit may be open transition or closed transition, regardless of Maintenance or Failsafe bypass

Maintenance Bypass (All manufacturers offer this type) Advantages: Disadvantages: Can bypass the ATS portion of the unit without disturbing the load Cannot bypass the ATS portion of the unit to the alternate source. RTB(D) - Load Break design (Break-Before- Make Bypass) NORMAL LOAD EMERGENCY NORM ISOLATE ATS BPN BPE AUTO Design relies on both electrical and mechanical interlocking, arguably reducing reliability. (This interlocking cannot be isolated, so unit must be taken completely off line for servicing.) Routine maintenance on ATS portion of units is possible with by no interruption to the load. X

Maintenance Bypass design Handle LOAD BYPASSED TO NORMAL ATS ATS Contacts are electrically interlocked to prevent bypassing to the alternate source, thus connecting normal and emergency sources together. NORM NORM NORM NORM ISOLATE Load Break Contacts Load Break Contacts Load Break Contacts Load Break Contacts Load Break Contacts Load Contacts Overlap Bypass Handle Bypass Handle AUTO AUTO BPN BPE Load Momentarily Disconnected Load Momentarily Disconnected Load Momentarily Disconnected BPN BPN BPN BPE BPE Bypass Handle Bypass Handle Bypass Handle Bypass Handle Bypass Handle Bypass Handle Bypass Handle Bypass Handle Emergency Power Available LOAD LOAD LOAD LOAD BYPASSED TO NORMAL LOAD BYPASSED TO NORMAL LOAD BYPASSED TO NORMAL Switch Bypassed to Emergency Maintenance Bypass design NORMAL EMERGENCY EMERGENCY EMERGENCY

X Bypass Handle LOAD BYPASSED TO NORMAL Load Break Contacts Load Break ATS ATS X NORM NORM NORM NORM ISOLATE Load Break Contacts Load Break Contacts Load Break Contacts Load Break Contacts Load Break Contacts Bypass Handle Bypass Handle AUTO AUTO BPN BPE Load Momentarily Disconnected Load Momentarily Disconnected Load Momentarily Disconnected BPN BPN BPN BPE BPE Bypass Handle Bypass Handle Bypass Handle Bypass Handle Bypass Handle Bypass Handle Bypass Handle Bypass Handle Emergency Power Available LOAD LOAD LOAD LOAD BYPASSED TO NORMAL LOAD BYPASSED TO NORMAL LOAD BYPASSED TO NORMAL Switch Bypassed to Emergency NORMAL EMERGENCY EMERGENCY EMERGENCY

Failsafe Bypass Switches (Where simplicity of operation is critical during an emergency condition) Load Contacts Diagram showing a normal operating state.

Failsafe Bypass Switches Bypass operation Load Contacts Bypass Handle

Failsafe Bypass Switches Bypassing to normal Load Break Contacts Bypass Handle Load Momentarily Disconnected

Failsafe Bypass Switches NORMAL LOAD EMERGENCY NORM ISOLATE ATS BPN BPE AUTO Isolating the ATS Portion LOAD BYPASSED TO NORMAL

Failsafe Bypass Switches NORMAL LOAD EMERGENCY NORM ISOLATE ATS BPN BPE AUTO LOAD BYPASSED TO NORMAL NORMAL LOAD EMERGENCY NORM ISOLATE ATS BPN BPE AUTO Isolating the ATS Portion LOAD BYPASSED TO NORMAL

Failsafe Bypass Switches NORMAL LOAD EMERGENCY NORM ISOLATE ATS BPN BPE AUTO LOAD BYPASSED TO NORMAL NORMAL LOAD EMERGENCY NORM ISOLATE ATS BPN BPE AUTO If the transfer switch portion is bypassed & isolated to normal. If the normal power fails an engine start signal will initiate... LOAD BYPASSED TO NORMAL

Failsafe Bypass Switches NORMAL LOAD EMERGENCY NORM ISOLATE ATS BPN BPE AUTO LOAD BYPASSED TO NORMAL NORMAL LOAD EMERGENCY NORM ISOLATE ATS BPN BPE AUTO If the transfer switch portion is bypassed & isolated to normal. if the normal power fails an engine start signal will initiate... LOAD BYPASSED TO NORMAL

Failsafe Bypass Switches NORMAL LOAD EMERGENCY NORM ISOLATE ATS BPN BPE AUTO Emergency Power Available LOAD STILL BYPASSED TO NORMAL

Failsafe Bypass Switches NORMAL LOAD EMERGENCY NORM ISOLATE ATS BPN BPE AUTO Switch Bypassed to Emergency

Failsafe Bypass Switches Should Normal Source return switch can still be racked in…

Failsafe Bypass Switches ATS RTB(D) - Load Break design (Break-Before- Make Bypass) NORM ISOLATE AUTO BPN BPE BPN BPE Should Normal Source return switch can still be racked in… LOAD NORMAL EMERGENCY