Honeywell HVAC400x Applications Manual page 154

HVAC400X – APPLICATION MANUAL
To adjust the intervals of the autochange, use P3.15.5 Autochange Interval. You can set the maximum number of
motors that can operate with parameter Autochange: Motor Limit (P3.15.7). You can also set the maximum
frequency of the regulating motor (Autochange: Frequency Limit P3.15.6).
When the process is in the limits that are set with parameters P3.15.6 and P3.15.7, the autochange occurs. If the
process is not in these limits, the system will wait until the process is in the limits, and do the autochange after that.
This prevents sudden pressure drops during the autochange when a high capacity at a pump station is necessary.
EXAMPLE
After an autochange, the first motor is put last. The other motors move up one position.
The start sequence of the motors: 1, 2, 3, 4, 5
--> Autochange -->
The start sequence of the motors: 2, 3, 4, 5, 1
--> Autochange -->
The start sequence of the motors: 3, 4, 5, 1, 2
P3.15.5 AUTOCHANGE INTERVAL (ID 1029)
You can use this parameter to adjust the autochange intervals.
This parameter defines how often to rotate the starting order of the motors/pumps. The autochange is done when
the number of running motors is below the autochange motor limit and the frequency is below the autochange freq
limit.
When the autochange interval has elapsed, the autochange occurs if the capacity is below the level set with
P3.15.6. and P3.15.7.
P3.15.6 AUTOCHANGE: FREQUENCY LIMIT (ID 1031)
You can use this parameter to set the autochange frequency limit.
An autochange is done when the autochange interval has elapsed, the number of running motors is less than
autochange motor limit and the controlling drive is running below autochange frequency limit.
P3.15.7 AUTOCHANGE: MOTOR LIMIT (ID 1030)
You can use this parameter to set the number of pumps used in Pump and Fan Cascade function.
An autochange is done when the autochange interval has elapsed, the number of running motors is less than
autochange motor limit and the controlling drive is running below autochange frequency limit.
P3.15.8 BANDWIDTH (ID 1097)
You can use this parameter to set the bandwidth area around the PID setpoint for starting and stopping of the
auxiliary motors.
When the PID feedback value stays in the bandwidth area, the auxiliary motors do not start or stop. The value of
this parameter is given as a percentage of the setpoint.
P3.15.9 BANDWIDTH DELAY (ID 1098)
You can use this parameter to set the duration before the auxiliary motors start or stop.
When the PID feedback is not in the bandwidth area, the time that is set with this parameter must go before the
auxiliary motors start or stop. The number of pumps that operate increases or decreases, if the PID controller
cannot keep the process value (feedback) in the specified bandwidth around the setpoint.
The bandwidth area is specified as a percentage of the PID setpoint. When the PID feedback value stays in the
bandwidth area, it is not necessary to increase or decrease the number of pumps that operate.
When the feedback value goes out of the bandwidth area, the quantity of time specified by parameter P3.15.8 must
go before the number of pumps that operate increases or decreases. More pumps must be available.
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