64 RT-SVX34C-EN
Startup
Two of the three methods for determining the suitability of the outside air can be selected utilizing
the potentiometer on the Economizer Actuator, as described below:
1. Ambient Temperature - controlling the economizing cycle by sensing the outside air dry bulb
temperature. Table 22 lists the selectable dry bulb values by potentiometer setting.
2. Reference Enthalpy - controlling the economizer cycle by sensing the outdoor air humidity.
Ta b le 22 lists the selectable enthalpy values by potentiometer setting. If the outside air enthalpy
value is less than the selected value, the economizer is allowed to operate.
3. Comparative Enthalpy - By utilizing a humidity sensor and a temperature sensor in both the
return air stream and the outdoor air stream, the economizer will be able to establish which
conditions are best suited for maintaining the zone temperature, i.e., indoor conditions or
outdoor conditions.
Gas Heat Control
The ignition sequence and timing are provided by a separate heat control module. The RTRM only
provides the heating outputs to initiate 1st and 2nd stages and control the combustion blower
relays. Both stages of the furnace, when initiated after each cycle, will start and operate for one
minute then cycle back if only one stage is required. Units with modulating heat capabilites will
light on high fire for one minute and then modulate to the appropriate heating rate for the building
load present.
When the fan selection switch is in the "AUTO" mode, the fan will be delayed from coming on for
approximately 30 seconds after a call for heat has been initiated. The fan will remain on for
approximately 90 seconds after the heating setpoint has been satisfied.
Electric Heat Control
The RTRM provides two heating outputs for 1st and 2nd stages with a 10 second delay between
each stage. When the fan selection switch is in the "AUTO" mode, the fan will start approximately
1 second before the 1st heater stage is activated. The fan and heater will cycle off after the heating
setpoint has been satisfied.
Clogged Filter Option
The unit mounted clogged filter switch monitors the pressure differential across the return air
filters. It is mounted in the filter section and is connected to the RTOM. The switch is adjustable and
Table 21. Economizer Effectiveness
Method used to determine econmizer
effectiveness Required
Comparative Enthalpy OAT, OAH, RAT, RAH
Reference Enthalpy OAT, OAH
Reference Dry Bulb OAT
Unable to determine effectiveness OAT data is invalid or unavailable
Table 22. Economizer Configuration
Selection Dry Bulb Enthalpy Value
A 73°F 27 BTU/LB Air
B 70 25 BTU/LB Air
C 67 23 BTU/LB Air
D 63 22 BTU/LB Air
E 55 19 BTU/LB Air
To Next Page
Loading...
