Applications Guide Tracer Graphical Programming - Trane
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Applications Guide Tracer Graphical Programming - Trane

Applications Guide Tracer Graphical Programming - Trane Applications Guide Tracer Graphical Programming - Trane

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28.09.2014 Views

® Chapter 4 Cooling tower with two-speed fan example • Alarms related to monitoring the sump temperature require timebased control. How is time-based control implemented in graphical programming? • All temperature sensors must be monitored for failure. • How is an alarm-reset function incorporated in a program? Adding the input blocks Begin by adding blocks to represent the inputs to this part of the program. To add the input blocks: 1. Place four Input (Hardware) blocks in the design space and assign the following analog inputs to them: • Sump Temp • Supply Temp • Return Temp • Outdoor Air Temp 2. Place three Variable blocks in the design space and assign the following variables to them (Figure 50): • Sump Alarm Setpoint (analog, sourced from the operator display/ service tool) • Pump Fail (binary, sourced from the program) • Alarm Reset (binary, sourced from the operator display/service tool and the program) Figure 50: Input blocks for the alarms module 54 CNT-APG001-EN

® Writing the alarms module Adding the output block ◆ Place an Output (Hardware) block in the design space and assign the binary output Alarm to it (Figure 51). Figure 51: Alarms module output Monitoring the sump temperature First, focus on the requirement dealing with monitoring the sump temperature.Besuretopayattentiontothekeywordsshowninitalics. They help indicate which blocks to use. If the sump temperature remains below 36°F (this value is adjustable at the operator display) for 15 minutes, or if the sump temperature falls below 32°F, indicate an alarm at the operator display and turn on the alarm output. Comparing the sump temperature with the sump alarm setpoint and the freezing point Apply a Less Than block to determine if the Sump Temperature is less than the Sump Alarm Setpoint. And apply a Less Than or Equal block to compare the Sump Temperature to the freezing point, 32°F. Use a Constant block to represent the freezing point. To compare the sump temperature with the sump alarm setpoint and the freezing point: 1. Add a Constant block to the design space and assign the value 32.0 to it to represent the freezing point. 2. Add a Less Than block and a Less Than or Equal block to the design space. CNT-APG001-EN 55

®<br />

Chapter 4 Cooling tower with two-speed fan example<br />

• Alarms related to monitoring the sump temperature require timebased<br />

control. How is time-based control implemented in graphical<br />

programming?<br />

• All temperature sensors must be monitored for failure.<br />

• How is an alarm-reset function incorporated in a program?<br />

Adding the input blocks<br />

Begin by adding blocks to represent the inputs to this part of the program.<br />

To add the input blocks:<br />

1. Place four Input (Hardware) blocks in the design space and assign the<br />

following analog inputs to them:<br />

• Sump Temp<br />

• Supply Temp<br />

• Return Temp<br />

• Outdoor Air Temp<br />

2. Place three Variable blocks in the design space and assign the following<br />

variables to them (Figure 50):<br />

• Sump Alarm Setpoint (analog, sourced from the operator display/<br />

service tool)<br />

• Pump Fail (binary, sourced from the program)<br />

• Alarm Reset (binary, sourced from the operator display/service<br />

tool and the program)<br />

Figure 50: Input blocks for the alarms module<br />

54 CNT-APG001-EN

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