Applications Guide Tracer Graphical Programming - Trane
Applications Guide Tracer Graphical Programming - Trane
Applications Guide Tracer Graphical Programming - Trane
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Chapter 5 Cooling tower with variable-speed fan example<br />
Reviewing the sequence of operation<br />
In this scenario a cooling tower with a variable-speed fan delivers condenser<br />
water to a small chiller plant. The following specifications apply to<br />
control of the cooling tower.<br />
Condenser water pump<br />
When condenser water is requested by the chiller plant, command the<br />
condenser water pump to start. If condenser water flow fails to be confirmed<br />
within 30 seconds, command the pump to stop and indicate a<br />
pump failure at the operator display and turn on the alarm output. A user<br />
must be able to reset the alarm at the operator display.<br />
Cooling tower fan<br />
Upon successful confirmation of condenser water flow, and when the cooling<br />
tower supply water temperature exceeds the setpoint by 2.5°F, turn<br />
on the fan. Modulate the fan to maintain the condenser water supply temperature<br />
according to setpoint. When the cooling tower supply water temperature<br />
is 2.5°F below the setpoint, turn off the fan. Note that the<br />
setpoint is adjustable from the operator display and that it is limited to a<br />
minimum of 65°F and a maximum of 95°F.<br />
Sump heater<br />
Cycle the sump heater if the sump temperature falls below 40°F (this<br />
value is adjustable at the operator display). If the outdoor air temperature<br />
falls below 32°F, turn on the sump heater continuously. If the sump<br />
temperature remains below 36°F (this value is adjustable at the operator<br />
display) for 15 minutes, or if the sump temperature falls below 32°F, indicate<br />
an alarm at the operator display and turn on the alarm output.<br />
Alarms<br />
In addition to the alarm requirements mentioned above, indicate an<br />
alarm at the operator display and turn on the alarm output when any<br />
sensor, including temperature and humidity, fails. Alarms must be resettable<br />
at the operator display.<br />
Calculations<br />
Calculate and display the change in water temperature across the cooling<br />
tower, the ambient wet-bulb temperature, and the approach temperature.<br />
(The approach temperature is defined as the difference between the ambient<br />
wet-bulb temperature and the condenser water supply temperature.)<br />
Thespecificationsforthepumpandthefanhavechanged.Thealarms<br />
have changed a little bit with the addition of the humidity sensor failure.<br />
The calculations section is completely new.<br />
80 CNT-APG001-EN
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