106
RTAA-IOM-3
Chilled Water Reset (CWR)
As an option, the UCM will reset the
chilled water temperature setpoint,
based on either the return water
temperature, zone air temperature, or
outdoor air temperature. The following
are selectable:
1. One of four RESET TYPEs, from top
to bottom in order of reset:
no CWR
RETURN WATER
TEMPERATURE RESET ZONE
TEMPERATURE RESET
OUTDOOR AIR TEMPERATURE
RESET
The UCM will not permit more than
one type of reset to be selected in
Menu 3.
2. RESET RATIO Setpoints. For
OUTDOOR AIR TEMPERATURE
RESET, there are both positive and
negative reset ratios.
3. START RESET Setpoints.
4. MAXIMUM RESET Setpoints. The
maximum resets are with respect to
the chilled water setpoint.
No matter which type of reset is
selected, all parameters are factory set
to a predetermined set of values. Field
adjustment of 2, 3, or 4, above, is
usually not required.
The equations for each type of reset
are:
RETURN WATER TEMPERATURE
RESET
CWS’= CWS + RESET RATIO
[START RESET - (TWE - TWL)]
and CWS’> or = CWS
and CWS’- CWS < or = MAXIMUM
RESET
ZONE TEMPERATURE RESET
CWS’= CWS + RESET RATIO
[START RESET - TZONE]
and CWS’> or = CWS
and CWS’- CWS < or = MAXIMUM
RESET
OUTDOOR AIR TEMPERATURE RESET
CWS’= CWS + RESET RATIO
[START RESET - TOD]
and CWS’> or = CWS
and CWS’- CWS < or = MAXIMUM
RESET
CWS’ is the new chilled water setpoint.
CWS is the active chilled water setpoint
before any reset has occurred.
RESET RATIO is a user adjustable gain.
START RESET is a user adjustable
reference.
TZONE is the zone temperature.
TOD is the outdoor temperature.
TWE is the entering evaporator water
temperature.
TWL is the leaving evaporator water
temperature.
MAXIMUM RESET is a user adjustable
limit, providing the maximum amount
of reset.
Note:
When any type of CWR is
enabled, the UCM will step the CWS
toward the desired CWS’ (based on the
above equations and setup
parameters) at a rate of 1 F every 5
minutes. This applies when the chiller
is both running and off. Normally the
chiller will start at the Differential-to-
Start value above a fully reset CWS or
CWS’.
The values for RESET RATIO for each type of reset are:
Reset
Increment
Factory
Reset
Ratio
English
Increment
Default
Type
Range
Units
Sl Units
Value
Return
10 to 120%
1%
1%
50%
Zone
50 to 300%
1 %
1 %
100%
Outdoor
80 to -80%
1 %
1 %
10%
The values for START RESET for each type of reset are:
Start
Increment
Factory
Reset
Reset
English
Increment
Default
Type
Range
Units
Sl Units
Value
Return
4 to 30 F
1 F
0.1 C
10 F (5.6 C)
(2.2 to 16.7 C)
Zone
55 to 85 F
1 F
0.1 C
78 F (25.6 C)
(12.8 to 29.4 C)
Outdoor
50 to 130 F
1 F
0.1 C
90 F (32.2 C)
(10 to 54.4 C)
The values for MAXIMUM RESET for each type of reset are:
Maximum
Increment
Factory
Reset
Reset
English
Increment
Default
Type
Range
Units
Sl Units
Value
Return
0 to 20 F
1 F
0.1 C
5 F (2.8 C)
(-17.8 to -6.7 C)
Zone
0 to 20 F
1 F
0.1 C
5 F (2.8 C)
(- 17.8 to -6.7 C)
Outdoor
0 to 20 F
1 F
0.1 C
5 F (2.8 C)
(- 17.8 to -6.7 C)
Summary of Contents for RTAA-130
Page 2: ... American Standard Inc 1991 ...
Page 8: ...8 RTAA IOM 3 ...
Page 24: ...24 RTAA IOM 3 ...
Page 50: ...50 RTAA IOM 3 Figure 30 Refrigerant Circuit Identification ...
Page 52: ...52 RTAA IOM 3 Figure 31 Remote Evaporator Piping Example ...
Page 59: ...59 RTAA IOM 3 Continued from Previous Page See Notes on Next Page ...
Page 63: ...63 RTAA IOM 3 Continued from Previous Page See Notes on Page 61 ...
Page 65: ...65 RTAA IOM 3 Continued from Previous Page See Notes on Page 61 ...
Page 76: ...76 RTAA IOM 3 ...
Page 92: ...92 RTAA IOM 3 Figure 51 Operator Interface Controls ...
Page 120: ...120 RTAA IOM 3 ...
Page 127: ...127 RTAA IOM 3 Continued from Previous Page 2307 1566C ...
Page 128: ...128 RTAA IOM 3 Figure 57 Unit Sequence of Operation RTAA 130 to 200 Tons 2306 9122A ...
Page 132: ...132 RTAA IOM 3 Figure 58 Operator s Log ...
Page 138: ...138 RTAA IOM 3 ...