Modulating Power Exhaust; Mechanical Cooling Without An Economizer (Cv And Sz Vav) - Trane Voyager Commercial Installation, Operation And Maintenance Manual

S S t t a a r r t t u u p p
Because of the spread between the heating and cooling
setpoints, the control will choose to control the
economizer at an offset temperature of 1.5°F below the
cooling setpoint. This will be the highest resulting
control setpoint temperature while maintaining the
least amount of offset.
The percentage that the economizer dampers open is
based on two factors:
• The zone temperature minus the economizer
setpoint, and,
• The zone temperature minus the outdoor air
temperature.
N N o o t t e e : : The following table lists the percentages the
dampers will open based on these conditions.
Table 22. Percent of damper travel
Zone Temp - Econ Setpoint °F
Zone - 0.0- 0.5-
ODT 0.5 1.0
0 - 7°F 0% 3%
7 - 14°F 0% 2%
> 14°F 0% 1%
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:
• The economizer dampers have been fully open for
three minutes, and;
• 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 " " O O n n " " , and is closed
when the supply fan is " " O O f f f f " " . The mechanical cooling
will cycle as though the unit had no economizer.
46
>-
1.0- 2.0- 3.0-
2.0 3.0 5.0 5.0
10-
9% 30% 90%
0%
10-
6% 20% 60%
0%
10-
3% 10% 30%
0%

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 and SZ VAV)
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. Table 23, p. 46
compressor staging sequence for standard efficiency
units.
For high efficiency units there are three separate
staging sequences which determine the staging of 3
compressors within each sequence. Each call for cool
will operate within a given sequence and the next call
for cool will operate in the next sequence. Lead/Lag
operation is taken into consideration with these 3
staging sequences and will be active when Lead/Lag is
configured. Table 24, p. 47
sequence for high efficiency units.
Table 23. Compressor staging with lead/lag disabled
- std efficiency units (excluding 40–50T CV
units)
"ON"
Unit Step Step
Model 1 2
CPR 1 CPR
27.5 - 35
(a) 1, 2
CPR 1 CPR 2
40
(b) (c)
CPR 1 CPR
50
(b) 2,3 (d)
(a) Single circuit, dual manifolded compressors
(b) Number one refrigeration circuit, Standalone compressor, is "On".
(c) First stage is off. Number two refrigeration circuit, standalone
compressor, is "On"
First Stage is "Off", Number two refrigeration circuit, manifolded
(d)
compressor pair operating simultaneously, is "On".
lists the
lists the compressor staging
"OFF"
Step Step Step Step
3 3 2 1
CPR
N/A N/A CPR 1
1, 2
CPR CPR CPR 2 CPR 1
1, 2 1, 2 (c) (b)
CPR CPR
CPR CPR 1
1, 2, 1, 2,
2, 3 (d) (b)
3 3
RT-SVX34R-EN