Ramp Loading; Surge Correction Control - Carrier SmartVu Control Manual

SRDC-UG-2-14-000 REVISION DATE PAGE
19 Series Carrier®
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TM
SmartVu 2.3 Dec 4, 2020 75 OF 168
Controls IOM
When chiller is running normally, the control will get input from capacity control to see whether to change
VFD TARGET SPEED and how much to change.
When chiller is in shut down process, VFD TARGET SPEED will be set to minimum VFD speed.
Af ter the compressor relay is cut off, VFD TARGET SPEED will be set to 0.

5.9. Ramp Loading

The ramp loading control slows down the rate at which the compressor loads up. This control can
prevent the compressor from loading up during the short period of time when the chiller is started and
the chilled water loop has to be brought down to CONTROL POINT (Setpoint Table). This helps reduce
electrical demand charges by slowly bringing the chilled water to CONTROL POINT. The total power
draw during this period remains almost unchanged.
There are two methods of ramp loading:
Temperature ramp loading shall limit the rate at which the controlled water temperature decreases for
cooling and increase for heating during ramping by reducing on cooling mode and increasing on heating
the Pulldown Set Point (Maintenance Menu - Capacity) at the configured rate until the pulldown setpoint
is less than for cooling mode Control point or greater than Control point for heating mode
Pull down ramp type shall be configured to 0 for temperature ramping.
Motor load ramp loading shall limit the rate at which either the percent load current or motor percent
kilowatts increases by incrementing the ramp demand limit at the configured rate.
Pull down ramp type shall be configured to 1 for load ramping.
PULLDOWN RAMP TYPE (Configuration Menu – General Configuration) is configured to 1 then motor
load shall determine the ramp rate. If DEMAND LIMIT SOURCE (Configuration Menu – General
Conf iguration) is set to AMPS then PERCENT LOAD CURRENT shall be used as motor load. If
DEMAND LIMIT SOURCE is set to kW then MOTOR PERCENT KILOWATTS shall be used as motor
load
The motor load ramp algorithm shall be deactivated when the Ramp Demand Limit is greater than or
equal to the ACTIVE DEMAND LIMIT (General Parameters). It shall also be deactivated when Ramp
Demand Limit is greater or equal to 80%. There shall be one minute delay for the compressor to be
uploaded to target load after ramping load demand limit is set to 80%.
If the power outage more than 3 hours, then Temperature Ramp Loading will be used regardless user
conf iguration. And the minimum loading rate (1^F/min) will be used.
5.10.

Surge Correction Control

There are two stages for surge correction, surge prevention control and surge protection control.
Lif t is defined as the difference between the saturated temperature at the impeller eye and at the
impeller discharge. The maximum lift a particular impeller wheel can perform varies with the gas flow
across the impeller and the size of the wheel.
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