Ramp Loading; Temperature Reset - Carrier AquaForce B Series Controls, Start-Up, Operation, Service And Troubleshooting Instructions

DISPLAY NAME
Master/Slave Select
Master Control Type
Slave Address
Lead Lag Select
Lead/Lag Balance Delta
Lead/Lag Start Timer
Lead Pulldown Time
Start If Error Higher
Lag Minimum Running Time
Lag Unit Pump Control
Chiller In Series
NOTES:
1. If pump control is configured to OFF (Master), then LAG UNIT (Slave) PUMP
SELECT (page 3 of the Master/Slave Config menu) = 1. If pump control is
set to any other value, then LAG UNIT (Slave) PUMP SELECT = 0. This con-
figuration must be set consistently for both master and slave chillers.
2. For Master/Slave Series Chiller Application, Master Chiller should always be
downstream of Slave.
DUAL CHILLER PUMP
CHILLER APPLICATIONS
Pump control for series chiller applications is controlled by the
master chiller only. The control of the slave chiller is directed
through commands transmitted by the master chiller. The slave
chiller has no action in master/slave operations. The slave
chiller only verifies that CCN communication with the master
chiller is present. See the Dual Chiller Sequence of Operation
section on page 55. Figure 36 shows a typical pump arrange-
ment for dual chiller series applications.

Ramp Loading

The Ramp Loading function limits the rate of change of the leav-
ing fluid temperature. The minimum compressor speed is calculat-
ed based on saturated condensing temperature and saturated suc-
tion temperature. To enable the Ramp Loading sequence:
DISPLAY NAME PATH

Main Menu
Ramp Loading
Configuration Menu
Enable
General Configuration

Main Menu
Cooling Ramp
Setpoint Table
Loading

Temperature Reset

The temperature reset function will determine the cooling con-
trol point. This control point is the active set point adjusted
with the current reset value:
Control Point = Setpoint + Reset
The purpose of this reset value is to decrease the required ca-
pacity if it is allowed by unit load operating conditions. When
a non-zero temperature reset is applied, the chiller controls to
the new control point instead of the set point. The type of tem-
perature reset is configured with the Cooling Reset Select vari-
able. Four types of temperature reset are available: Outdoor Air
Temperature, Return Water Reset (Delta T), 4 to 20mA control,
and Space Temperature control:
Table 29 — Slave Chiller Configuration in Series Applications

Main Menu Configuration Menu
CONTROL FOR SERIES
VALUE
Yes

Range: 0.2 to 2.0°F/min (0.1 to
1.1°C/min)
Default: 1.0°F/min (0.5°C/min)
PATH

Master/Slave Config
DISPLAY
NAME
Cooling Reset
Select
Under normal operation, the chiller will maintain a constant
entering or leaving fluid temperature, based on the configura-
tion, approximately equal to the chilled fluid set point. As the
evaporator load varies, the evaporator fluid temperature differ-
ence will change in proportion to the load. For example, if the
chiller was selected for an entering to leaving water tempera-
ture difference of 10°F (5.5°C) at full load, at 50% load the
temperature difference would be 5°F (2.2°C). See Fig. 37. Be-
cause the change in temperature through the evaporator is a
measure of the building load, the temperature difference reset
is the average building load. Usually the chiller size and fluid
temperature set point are selected based on a full load condi-
tion. At part load, the fluid temperature set point may be lower
than required. When the fluid temperature is allowed to in-
crease at part load, the efficiency of the machine will increase.
The chiller can also be set for return water temperature control.
See Fig. 38.
Other indirect means of estimating building load and con-
trolling temperature reset are also available and are discussed
below.
To verify that reset is functioning correctly, subtract the Cur-
rent Setpoint (Main Menu
Setpoint) from the Control Point (Main Menu

rameters Control Point) to determine the degrees reset.
38
VALUE
2 (Slave)
Default: 0 (Disable)
1=Local Control
2=Remote Control
3=CCN Control
Default: 1(Local)
Configure for proper control type.
Must be set to the Slave Chiller's address.
The master and slave chiller must have
different addresses and be on the same
Bus Number
Default: 2
0 (Master Always Leads)
1 (Lag Once Failed Only)
2 (Lead/Lag Runtime Select)
Default: 0 (Master Always Leads)
Range: 40 to 400 hours
Default: 168 hours
Range: 2 to 30 minutes
Default: 10 minutes
Range: 0 to 60 minutes
Default: 0 minutes
Range: 3.0 to 18°F (1.7 to 10.0°C)
Default: 4.0°F (2.2°C)
Range: 0 to 150 minutes
Default: 0 minutes
0 (Stop If Unit Stops)
1 (Run If Unit Stops)
Default: 0 (Stop If Unit Stops)
Yes (In Series)
Default: No
PATH

Main Menu 0 = None

Configuration Menu 1 = OAT
Reset Configuration 2 = Delta T
3 = 4 to 20 mA Control
4 = Space Temp

General Parameters
VALUE

Current

General Pa-