![Figure 1-11_thumb[1]](http://machineryequipmentonline.com/electric-equipment/wp-content/uploads/2020/06/Figure-1-11_thumb1.jpg "Figure 1-11_thumb[1]")
Shown in Fig. 1-11:
Line 6 The first element is a Normally Open contact of R1 which will be closed if the panel has power. The next element is a Normally Open contact of R2. The next element is time delay relay R4. The logic is that if the panel has power and the R2 relay is latched, then the timer will start. R4 has a Normally Open contact on lines 9 and 13. The Normally Open, time-closed contact is on line 8.
![Figure 1-12_thumb[1]](http://machineryequipmentonline.com/electric-equipment/wp-content/uploads/2020/06/Figure-1-12_thumb1.jpg "Figure 1-12_thumb[1]")
Shown in Fig. 1-12:
Line 7 The first element is the Selector switch. The OXO indicates that the contact is closed in the test mode. The next element is the R5 relay. The R5 relay has Normally Open contacts in lines 14, 15, and 21 and a Normally Closed contact in line 9. The logic is that when the Selector switch is in the center position, test mode, relay R5 will be energized. The 3-Cont, SS-Cont, and 2-Cont indicate that the number 3 and 2 wires and Selector switch mechanical operator continue to the next page.
![Figure 1-13_thumb[1]](http://machineryequipmentonline.com/electric-equipment/wp-content/uploads/2020/06/Figure-1-13_thumb1.jpg "Figure 1-13_thumb[1]")
In Fig. 1-13, the 3-Cont, SS-Cont, and 2-Cont indicate that the number 3 and 2 wires and the Selector switch mechanical operator continue from the previous page.
Line 8 The first element is a Normally Open, time-closed contact from relay R4. The next element is relay R6. The logic is that after relay R4 has timed out, the contact will close, and relay R6 will be energized. Relay R6 has a Normally Open contact on line 9 and a Normally Closed contact on line 9.
![Shown in Fig. 1-14_thumb[1]](http://machineryequipmentonline.com/electric-equipment/wp-content/uploads/2020/06/Shown-in-Fig.-1-14_thumb1.jpg "Shown in Fig. 1-14_thumb[1]")
Shown in Fig. 1-14:
Line 9 The first element is a Normally Open contact of relay R4. The next element is a Normally Closed contact of relay R5. The next element is a Normally Closed contact of relay R6. In the next line down, the first element is a Normally Open contact of relay R2. The next element is a Normally Open contact of relay R6. The next element is a Normally Closed time-open contact of time delay relay R10. The logic is that if relay R4 is closed and relay R5 is closed and relay R6 is closed or relay contact R2 is closed and relay contact R6 is closed and relay contact R10 is closed, then relay R7 will be energized. Relay R7 is the main alarm relay and triggers the output contacts. Relay R7 has Normally Open contacts on lines 10, 12, 16, and 22. Three Normally Open output contacts are on terminals 48 to 53. These contacts are for the CPC shunt trip cir- cuits. One Normally Open contact is on terminals 54 and 55, a fire alarm system monitoring circuit.
![Figure 1-15_thumb[1]](http://machineryequipmentonline.com/electric-equipment/wp-content/uploads/2020/06/Figure-1-15_thumb1.jpg "Figure 1-15_thumb[1]")
Shown in Fig. 1-15:
Line 10 The first element is a Normally Open contact of relay R7, and the next element is relay R8. The logic is that when R7 closes, relay R8 will be energized. This relay is needed to give more contacts 8 to the function of the R7 relay. Relay R8 has Normally Open contacts on line 26. Three Normally Open output contacts are on terminals 58 to 63. These contacts are for the CRAC shunt trip circuits. One Normally Open contact is on terminals 64 and 65, a fire alarm system damper shutdown.
![Figure 1-16_thumb[1]](http://machineryequipmentonline.com/electric-equipment/wp-content/uploads/2020/06/Figure-1-16_thumb1.jpg "Figure 1-16_thumb[1]")
Shown in Fig. 1-16:
Line 11 The first element is a Normally Open contact of the Selector switch. The OOX indicates Selector switch maint (maintenance) mode. The next element is relay R9. The logic is thus: When the Selector switch is in the maint mode position, then relay R9 will be energized. Relay R9 has a Normally Open contact on lines 18 and 23 and a Normally Open contact on terminals 66 and 67. The Selector switch is in the maint position, all controls are inactive, and the pilot light will be energized. Also, the Modbus module will be altered.
![Figure 1-17_thumb[1]](http://machineryequipmentonline.com/electric-equipment/wp-content/uploads/2020/06/Figure-1-17_thumb1.jpg "Figure 1-17_thumb[1]")
Shown in Fig. 1-17:
Line 12 The first element is a Normally Open contact of relay R7. The next element is the time delay relay R10. The logic is thus: When the panel is in alarm, relay R7 will be energized and start the timer R10. Relay R10 has a time-open contact in line 9.
![Figure 1-18_thumb[1]](http://machineryequipmentonline.com/electric-equipment/wp-content/uploads/2020/06/Figure-1-18_thumb1.jpg "Figure 1-18_thumb[1]")
Shown in Fig. 1-18:
Line 13 The first element is a Normally Open contact of relay R1. The next element is a Normally Open contact of relay R4. The next element is a white pilot light. The logic is that when the panel has control voltage and the time delay relay R4 closes, the alarm pilot light will be illuminated.
![Figure 1-19_thumb[1]](http://machineryequipmentonline.com/electric-equipment/wp-content/uploads/2020/06/Figure-1-19_thumb1.jpg "Figure 1-19_thumb[1]")
Shown in Fig. 1-19:
Line 14 The first element is a Normally Open contact of relay R5. The next element is a Normally Open contact of relay R8. The next element is a white pilot light. The logic is that when relay R5 is ener- gized in test mode, and relay R8 is energized, the Test Complete pilot light will be illuminated.
![Figure 1-20_thumb[1]](http://machineryequipmentonline.com/electric-equipment/wp-content/uploads/2020/06/Figure-1-20_thumb1.jpg "Figure 1-20_thumb[1]")
Shown in Fig. 1-20:
Line 15 The first element is a Normally Open contact of relay R5. The next element is an amber pilot light. The logic is that when the relay R5 is energized in test mode, the Test Mode pilot light will be illuminated.
![Figure 1-21_thumb[1]](http://machineryequipmentonline.com/electric-equipment/wp-content/uploads/2020/06/Figure-1-21_thumb1.jpg "Figure 1-21_thumb[1]")
Shown in Fig. 1-21:
Line 16 The first element is a Normally Open contact of relay R7. The next element is a red pilot light. The logic is that when the relay R7 is energized in alarm mode, the Alarm Active pilot light will be illuminated until the time delay of relay R10.
The 3-Cont and 2-Cont indicate that the number 3 and 2 wires con- tinue to the next page.
![Figure 1-22_thumb[1]](http://machineryequipmentonline.com/electric-equipment/wp-content/uploads/2020/06/Figure-1-22_thumb1.jpg "Figure 1-22_thumb[1]")
In Fig. 1-22, the 3-Cont and 2-Cont indicate that the number 3 and 2 wires continue from the previous page.
Line 17 The first element is a Normally Open contact of latching relay R2. The next element is a red pilot light. The logic is that when the latching relay R2 is energized in alarm mode, the Critical Power Lost pilot light will be illuminated.
![Figure 1-23_thumb[1]](http://machineryequipmentonline.com/electric-equipment/wp-content/uploads/2020/06/Figure-1-23_thumb1.jpg "Figure 1-23_thumb[1]")
Shown in Fig. 1-23:
Line 18 The first element is a Normally Open contact of relay R9. The next element is a white pilot light. The logic is that when the Selector switch is in the maint mode position, the relay R9 is ener- gized. The Maintenance Mode pilot light will be illuminated.
![Figure 1-24_thumb[1]](http://machineryequipmentonline.com/electric-equipment/wp-content/uploads/2020/06/Figure-1-24_thumb1.jpg "Figure 1-24_thumb[1]")
Shown in Fig. 1-24:
Line 19 Power for the Modbus unit. The Modbus unit allows an interface to the control and monitoring system.
![Figure 1-25_thumb[1]](http://machineryequipmentonline.com/electric-equipment/wp-content/uploads/2020/06/Figure-1-25_thumb1.jpg "Figure 1-25_thumb[1]")
Shown in Fig. 1-25:
Line 20 The first element is a Normally Open contact of relay R3. The next element is the Modbus EPO Reset input. The logic is that when the system has been reset using the reset push button, the Modbus will receive the indication that this event has accorded and can be reported to the monitoring system.
![Figure 1-26_thumb[1]](http://machineryequipmentonline.com/electric-equipment/wp-content/uploads/2020/06/Figure-1-26_thumb1.jpg "Figure 1-26_thumb[1]")
Shown in Fig. 1-26:
Line 21 The first element is a Normally Open contact of relay R5. The next element is the Modbus EPO test input. The logic is that when the system has been put in the test mode using the Selector switch, the Modbus will receive the indication that this event has accorded and can be reported to the monitoring system.
![Figure 1-27_thumb[1]](http://machineryequipmentonline.com/electric-equipment/wp-content/uploads/2020/06/Figure-1-27_thumb1.jpg "Figure 1-27_thumb[1]")
Shown in Fig. 1-27:
Line 22 The first element is a Normally Open contact of relay R7. The next element is the Modbus EPO armed input. The logic is that when the system has been put in the armed mode using the Selector
switch and the system is alarmed using any of the devices, the Modbus will receive the indication that this event has accorded and can be reported to the monitoring system.
![Figure 1-28_thumb[1]](http://machineryequipmentonline.com/electric-equipment/wp-content/uploads/2020/06/Figure-1-28_thumb1.jpg "Figure 1-28_thumb[1]")
Shown in Fig. 1-28:
Line 23 The first element is a Normally Open contact of relay R10. The next element is the Modbus EPO maint mode input. The logic is that when the system has been put in the maint mode using the Selector switch, the Modbus will receive the indication that this event has accorded and can be reported to the monitoring system.
![Figure 1-29_thumb[1]](http://machineryequipmentonline.com/electric-equipment/wp-content/uploads/2020/06/Figure-1-29_thumb1.jpg "Figure 1-29_thumb[1]")
Shown in Fig. 1-29:
Line 24 The first element is a Normally Open contact of relay R1. The next element is the Modbus EPO power on input. The logic is that when the system has been put in control power, the Modbus will receive the indication that this event has accorded and can be reported to the monitoring system.
![Figure 1-30_thumb[1]](http://machineryequipmentonline.com/electric-equipment/wp-content/uploads/2020/06/Figure-1-30_thumb1.jpg "Figure 1-30_thumb[1]")
Figure 1-30 shows that R1 will close when there is power to the system panel circuit.
![Figure 1-31_thumb[1]](http://machineryequipmentonline.com/electric-equipment/wp-content/uploads/2020/06/Figure-1-31_thumb1.jpg "Figure 1-31_thumb[1]")
Figure 1-31 shows that R7 and R8 will close when there is an alarm. This will energize the shunt trip breakers and turn off all power to the CRAC units.
![Figure 1-32_thumb[1]](http://machineryequipmentonline.com/electric-equipment/wp-content/uploads/2020/06/Figure-1-32_thumb1.jpg "Figure 1-32_thumb[1]")
Figure 1-32 shows that R8 will close when there is an alarm, and R9 will close when the system is in the maint mode.
![Figure 1-33_thumb[1]](http://machineryequipmentonline.com/electric-equipment/wp-content/uploads/2020/06/Figure-1-33_thumb1.jpg "Figure 1-33_thumb[1]")
A notes section such as the one shown in Fig. 1-33 will have informa- tion that you cannot perceive by looking at the ladder diagram.
![Figure 1-34_thumb[5]](http://machineryequipmentonline.com/electric-equipment/wp-content/uploads/2020/06/Figure-1-34_thumb5.jpg "Figure 1-34_thumb[5]")
A bill of materials is useful if you need to replace a device or get the specifications for a device (Fig. 1-34).
![Figure 1-35_thumb[2]](http://machineryequipmentonline.com/electric-equipment/wp-content/uploads/2020/06/Figure-1-35_thumb2.jpg "Figure 1-35_thumb[2]")
To locate the devices on the panel, refer to the front panel display (Fig. 1-35).