Eaton EPCT Fire Series Installation Manual

20Automatic transfer switch (ATS)EPCT FirE sEriEs FirE PumP ConTrollEr MN124016EN August 2019 www.eaton.com6.0 Automatic transfer switch (ATS)6.1 GeneralTransfer switches are used to protect critical electrical loadsagainst loss of power. The load’s Source 1 power source isbacked up by a Source 2 power source. A transfer switchis connected to both the Source 1 and Source 2 powersources and supplies the load with power from one of thetwo sources. In the event that power is lost from Source1, the transfer switch transfers the load to the Source 2power source. Once Source 1 power is restored the load isautomatically transferred back to the Source 1 power source.The transfer switch will transfer to the backup source whenthe Source 1 power falls below or rises above a pre-setvoltage, frequency, or in the event of a phase reversal. Ifthe Source 2 power source is a standby generator the ATSwill initiate a generator start up. It will then transfer to theSource 2 power source once sufficient generator voltageis available. When Source 1 power is restored the ATSautomatically transfers back to the Source 1 and will initiatea generator engine shutdown.The transfer switch has four basic elements:1. Main contacts that connect and disconnect the loadfrom the Source 1 and Source 2 supplies.2. The ATS electrical control circuit that energizes thetransfer mechanism to switch the main contacts.3. The mechanical transfer mechanism that switchesthe main contacts.4. The ATS control board and touchscreen displaythat monitor the condition of the power sources andprovide intelligent decisions for the the operation ofthe transfer switch.6.2 Main contactsThe connection of the ATS load to either of the two sourcesupplies is managed through a pair of isolation switches.The normal isolation switch controls Source 1 while theemergency isolation switch controls Source 2. The mechanicalassembly that operates the isolation switches is designed toprevent both sources from feeding the load at the same time.The fire pump controller I/O board and the ATS control boardmonitor the source 1 and source 2 voltages at the line sideof the isolation switches. A set of auxiliary switches installedin each of the isolation switches provide positional feedbackto the ATS controller on which source is currently supplyingthe load. These auxiliary switches are connected to terminal68 (common), 70 (ATS Normal), and 71 (ATS Emergency). Ifthe ATS is in the Source 1 position then terminal 68 and 70will be closed and 68 and 71 will be open. If the ATS is in theSource 2 position then terminal 68 and 71 will be closed and68 and 70 will be open.6.3 ATS electrical control circuitWhen the ATS control board initiates a transfer to Source2 or Source 1 it will energize the 9CR relay located onthe ATS control board. Energizing this relay will result inclosure of the contact between terminals 72 & 73 on theATS board. Closing this contact will energize the ATS motorand the motor brake. The motor is supplied power fromone of two 120Vac secondary control power transformerssupplied by Source 1 and Source 2. The control powertransformer primary voltage is derived from the line side ofthe ATS isolation switches. The transformers provided in theassembly will depend on the line voltage of the customer’sapplication. To prevent the transformers from back feedingone another a factory supplied relay (KV) is used to isolatethe transformers from each other. This KV relay will energizewhenever Source 2 is present.6.4 Mechanical transfer mechanismThe smaller transfer switch controllers that use theF-Frame (150A) isolation switches have the fire pumpcontroller and transfer switch located in the sameenclosure. The transfer switch portion of the controller isseparated from the rest of the fire pump controller usinga white, metal barrier. A beam mechanism connects theisolation switch handles and the motor operator arm. Thebeam attaches to a mounting plate at a pivot point locatedbetween the isolation switches. The motor operator armrides in a track at the other end of the beam. As the motorarm rotates the beam pivots on its mount causing thenormal and emergency isolation switch handles to moveup or down. This will connect or disconnect Source 1 and2. At no time will both the normal and emergency sourcesbe connected at the same time. To manually rotate themotor, you must first de-energize the controller. The motoris located behind the operator arm on the mechanismmounting plate. Locate the clutch plate on the bottomof the motor towards the back of the enclosure. It is arectangular, gold coloured plate that has a small amount ofmovement. Press and hold the clutch plate to the motorframe. You will now be able to rotate the motor arm tomove the position of the beam.The larger transfer switch controllers that use the K-Frame(300A or 400A), L-Frame (600A), or N- Frame (800A or1200A) isolation switches have the transfer switch locatedin a separate enclosure. The separate enclosure is bolteddirectly to the fire pump controller enclosure. The transferswitch has a rotating metal handle and an arrow whichindicates the position of the transfer switch (normal/emergency/neutral). The ATS motor operator mechanism islocated behind the manual operator handle and cover plate.The motor operator mechanism connects to the handles ofthe isolation switches. As the motor operator mechanism ormanual operation handle rotates the normal and emergencyisolation switches connect and disconnect. At no time willboth the normal and emergency sources be connected atthe same time. To manually operate the transfer switch, youmust first de-energize the controller. After it is de-energizedyou may manually rotate the handle until the arrow aligns tothe desired transfer switch position.