General Information
16
RT-SVX24J-EN
Supply Air Temperature Low Limit
Uses the supply air temperature sensor input to modulate
the economizer damper to minimum position in the event
the supply air temperature falls below the occupied
heating setpoint temperature.
Discharge Line Thermostat for Evaporative
Condensers
The first compressor on each circuit is equipped with a
Discharge Line Thermostat. If the temperature of the line
exceeds 210°F the thermostat interrupts the 115V circuit for
the compressors and both of the compressors on that
circuit will be de-energized. Once the temperature drops
below 170°F the thermostat will close and allow the
compressor to be energized.
Freezestat
A binary input device used on CV and VAV units with
Hydronic Heat. It is mounted in the heat section and
connected to the Heat Module. If the temperature of the air
leaving the heating coil falls to 40°F, the normally open
contacts on the freezestat closes signalling the Heat
Module and the Rooftop Module (RTM) to:
f. drive the Hydronic Heat Actuator to the full open
position
g. turn the supply fan “Off”
h. closes the outside air damper
i. turns “On” the SERVICE light at the Remote Panel
j. initiates a “Low Temp Limit” diagnostic to the
Human Interface
Compressor Circuit Breakers
The Scroll Compressors are protected by circuit breakers
which interrupt the power supply to the compressors if the
current exceeds the breakers “must trip” value. During a
request for compressor operation, if the Compressor
Module detects a problem outside normal parameters, it
turns any operating compressor(s) on that circuit “Off”,
locks out all compressor operation for that circuit, and
initiates a manual reset diagnostic (compressor trip).
Constant Volume (CV) Units
Zone Temperature—Cooling
Relies on input from a sensor located directly in the space,
while a system is in the occupied “Cooling” mode. It
modulates the economizer (if equipped) and/or stages the
mechanical cooling “On and Off” as required to maintain
the zone temperature to within the cooling setpoint
deadband.
Zone Temperature—Heating
Relies on input from a sensor located directly in the space,
while a system is in the occupied “Heating” mode or an
unoccupied period, to stage the heat “on and off” or to
modulate the heating valve (hydronic heat only) as
required to maintain the zone temperature to within the
heating setpoint deadband. The supply fan will be
requested to operate any time there is a request for heat.
On gas heat units, the fan will continue to run for 60
seconds after the furnace is turned off.
Figure 5.
Transducer voltage output vs. pressure input for supply, return and building pressure
-0.75 to 9.0 Iwc Pressure Transducer Voltage Output vs. Pressure Input
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
-0.
75
-0.
25
0.
25
0.
75
1.
25
1.
75
2.
25
2.
75
3.
25
3.
75
4.
25
4.
75
5.
25
5.
75
6.
25
6.
75
7.
25
7.
75
8.
25
8.
75
Pressure (inches w.c.)
Vo
lts
