Percent Capacity Output Option - Trane CGAM Installation & Operation Manual

Installation - Electrical
Chilled Water Reset (CWR)
CH530 resets the chilled water temperature set point
based on either return water temperature, or outdoor air
temperature.
The following shall be selectable:
• One of three ResetTypes: None, Return Water
Temperature Reset, Outdoor AirTemperature Reset, or
Constant Return WaterTemperature Reset.
• Reset Ratio Set Points.
• For outdoor air temperature reset there shall be both
positive and negative reset ratio's.
• Start Reset Set Points.
• Maximum Reset Set Points.
The equations for each type of reset are as follows:
Return
CWS' = CWS + RATIO (START RESET - (TWE -TWL))
and CWS' > or = CWS
and CWS' - CWS < or = Maximum Reset
Outdoor
CWS' = CWS + RATIO * (START RESET -TOD)
and CWS' > or = CWS
and CWS' - CWS < or = Maximum Reset
where
CWS' is the new chilled water set point or the "reset CWS"
CWS is the active chilled water set point before any reset
has occurred, e.g. normally Front Panel,Tracer, or ECWS
RESET RATIO is a user adjustable gain
START RESET is a user adjustable reference
TOD is the outdoor temperature
TWE is entering evap. water temperature
TWL is leaving evap. water temperature
MAXIMUM RESET is a user adjustable limit providing the
maximum amount of reset. For all types of reset, CWS' -
CWS < or = Maximum Reset.
Reset
Reset Ratio Start Reset
Type Range Range
4-30°F
10-
Return
120%
(2.2-16.7°C) (0.0-11.1°C)
50 - 130°F
80-
Outdoor
-80%
(10-54.4°C) (0.0-11.1°C)
In addition to Return and Outdoor Reset, the MP provides
a menu item for the operator to select a Constant Return
Reset. Constant Return Reset will reset the leaving water
temperature set point so as to provide a constant entering
water temperature.The Constant Return Reset equation is
76
Maximum Increment Factory
Reset Default
Range IP SI Value
0-20°F
1% 1% 50%
0 - 20°F
1% 1% 10%
the same as the Return Reset equation except on selection
of Constant Return Reset, the MP will automatically set
Ratio, Start Reset, and Maximum Reset to the following.
RATIO = 100%
START RESET = Design DeltaTemp.
MAXIMUM RESET = Design DeltaTemp.
The equation for Constant Return is then as follows:
CWS' = CWS + 100% (Design DeltaTemp. - (TWE -TWL))
and CWS' > or = CWS
and CWS' - CWS < or = Maximum Reset
When any type of CWR is enabled, the MP will step the
Active CWS toward the desired CWS' (based on the above
equations and setup parameters) at a rate of 1 degree F
every 5 minutes until the Active CWS equals the desired
CWS'.This applies when the chiller is running.
When the chiller is not running the CWS is reset
immediately (within one minute) for Return Reset and at a
rate of 1 degree F every 5 minutes for Outdoor Reset.The
chiller will start at the Differential to Start value above a
fully reset CWS or CWS' for both Return and Outdoor
Reset.

Percent Capacity Output Option

CH530 provides an optional percent capacity output for
those customers without a communicating BAS interface.
The active unit capacity (AUC) is provided through a 2-10
VDC analog output at 1A25 terminals J2-4 and J2-6 (GND).
The active unit capacity value (in %) can be derived from
the 2-10 VDC output voltage (OV) using the following
calculation:
AUC = 100*(OV - 2.0V)/(10.0V - 2.0V)
Note: The percent capacity output is based on the
number and size of compressors energized, and is
not adjusted for operating conditions.This value
cannot be used as an accurate measure of total unit
current, power or cooling capacity.
CG-SVX17E-EN