RT-SVX34C-EN 59
Startup
1. The zone temperature minus the economizer setpoint, and
2. The zone temperature minus the outdoor air temperature.
Note: Tabl e 19 lists the percentages the dampers will open based on these conditions.
While economizing, if the supply air temperature falls below 50°F, the damper will not be allowed
to open any further until the supply air temperature rises above 50°F. If the supply air temperature
falls below 45°F, the dampers will be driven to minimum position and held there until the supply
air temperature rises above 50°F.
The mechanical cooling is disabled while in an economizing state until two conditions are met;
1. The economizer dampers have been fully open for three minutes, and;
2. The calculated rate of change in the zone temperature is less than 12° F per hour.
If the economizer is disabled due to unsuitable conditions, the economizer is at the selected
minimum position when the supply fan is "On", and is closed when the supply fan is "Off". The
mechanical cooling will cycle as though the unit had no economizer.
Modulating Power Exhaust
If the unit is equipped with the modulating power exhaust option, the power exhaust actuator will
follow the position of the economizer actuator.
Mechanical Cooling without an Economizer (CV only)
Mechanical cooling is used to maintain the zone temperature. The RTRM is designed to limit the
compressor cycle rates to within 10 cycles per hour based on the minimum compressor "on" and
"off" times.
It stages the mechanical cooling to control the zone temperature to within +/- 2° F of the sensor
setpoint at the sensed location. Tab l e 2 0 lists the compressor stepping sequence.
Table 19. Percent of Damper Travel
Zone Temp - Econ Setpoint °F
Zone - ODT
0.0 - 0.5 0.5 - 1.0 1.0 - 2.0 2.0 - 3.0 3.0 - 5.0 > 5.0
0 - 7 F 0% 3% 9% 30% 90% 100%
7 - 14 F 0% 2% 6% 20% 60% 100%
> 14 F 0% 1% 3% 10% 30% 100%
Table 20. Compressor Staging with Lead/Lag Disabled
"ON" "OFF"
Unit Model Step 1 Step 2 Step 3 Step 3 Step 2 Step 1
27.5 - 35 CPR 1
1
CPR 1, 2 N/A N/A CPR 1, 2 CPR 1
1
40 CPR 1
2
CPR 2
3
CPR 1, 2 CPR 1, 2 CPR 2
3
CPR 1
2
50 CPR 1
2
CPR 2,3
4
CPR 1, 2, 3 CPR 1, 2, 3 CPR 2, 3
4
CPR 1
2
Notes:
1. Single circuit, dual manifolded compressors
2. Number one refrigeration circuit, Standalone compressor, is "On".
3. First stage is off. Number two refrigeration circuit, standalone compressor, is "On"
4. First Stage is "Off", Number two refrigeration circuit, manifolded compressor pair operating simultaneously, is "On".
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