RT-SVX34C-EN 57
Startup
Important: In order to avoid nuisance trips, the overload setpoint dial must be adjusted to the
following calculated value: Overload Setting = (Motor FLA) x 1.12
Overload Setting = (Compressor RLA) x 1.12
System Operation
Economizer Operation with a Conventional Thermostat (CV only)
If the ambient conditions are suitable for economizer operation, the economizer is activated as the
1st step of cooling from Y1. The dampers are controlled to provide a supply air temperature of 50°
F +/- 5° F. If the economizer is disabled due to ambient conditions, the 1st stage of mechanical
cooling is activated.
While economizing, if an additional stage of cooling is activated from Y2, the 1st stage of
mechanical cooling is activated. If the economizer is disabled due to ambient conditions, the 2nd
stage of mechanical cooling is activated.
The supply fan is activated from the G terminal and will cycle with a call for heat or cooling if in
the "Auto" mode. It will run continuously in the "On" mode regardless of any other system demand.
On gas heat units, first and second stages are activated by the W1 and W2 terminals on the CTI.
On electric heat units, only two stages of heat are available. If the W2 terminal is activated without
activating the W1 terminal, the RTRM will bring on both stages of electric heat.
The Conventional Thermostat connections can also be utilized as a generic building automation
system interface for constant volume ICS applications. Due to the limited heating and cooling steps
when using a conventional thermostat, compressor staging will vary on units with three
compressors.
Note: If a conventional thermostat is used with a unit that has modulating gas heat, the unit will
control to the Discharge Air SP potentiometer on the RTOM when heating with a W1 call
only. The unit will go to high fire with W1 + W2.
Microelectronic Control Features
1. Anti short cycle timer (ASCT) function. Compressor operation is programmed for 3 minutes of
minimum “ON” time, and 3 minutes of minimum “OFF” time. Enhances compressor reliability,
and ensures proper oil return.
Figure 38. Manual Motor Protectors
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