58 RT-SVX34C-EN
Startup
2. Delay between stages timer function. When combined with a standard Zone Sensor Module,
the Reliatel Refrigeration Module (RTRM) provides a 10 second minimum “ON” delay for
compressor staging.
3. Built in Fan Delay Relay function for Constant Volume Units. When the fan mode switch on the
Zone Sensor Module is set in the auto position, the RTRM provides individual supply fan timing
sequences for each system in heating and cooling. The RTRM provides different timing
sequences for Gas Heat units and Cooling only units.
4. Low ambient cooling to 0° F with Frostat™.
5. Built in electric heat staging, provides a 10 second “ON” delay between resistance heat stages.
6. Compressor cycle rate minimization, extends compressor life expectancy. Minimizes
damaging compressor inrush current, and guards against short cycling.
7. Economizer preferred cooling allows fully integrated economizer operation with mechanical
cooling if actually needed.
On constant volume applications, a 3 minute delay allows the RTRM to evaluate the rate of
change in the zone. If the zone temperature is dropping faster than acceptable parameters, the
compressor(s) will not be allowed to operate.
8. Free night setback allows the unit to enter an unoccupied mode by simply shorting across
terminals RTRM J6-11 and J6-12. The short can be achieved by a set of dry contacts or a time
clock. Once this short has been made the unit will close the economizer dampers, go from
continuous fan to auto fan operation, and:
CV Unit w/Mechanical ZSM
If the unit has a valid cooling and heating setpoint, the setup/setback is a minimum of 7°.
If the unit does not have both setpoints, the setup/setback is 0°.
If the unit has neither setpoint, the unoccupied cooling/heating setpoints will be 74°F/71°F.
This input is ignored if a conventional thermostat is used.
VAV unit w/o ICS or NSB engerizes heating if the space temperature drops to 10° F below the MWU
setpoint but not less than 50° F
This option can not be used with programmable ZSM or with an ICSTM system.
9. Low pressure cutouts on all compressors have been added to insure compressor reliability in
low refrigerant flow situations. The compressor(s) will lockout after four consecutive low
pressure control trips during the compressor minimum 3 minute "on" time. The lockout will
have to be manual reset as explained in this document.
Economizer Operation with CV Controls
The control point for the economizer is designed to control at least 1.5° F below the cooling setpoint
or 1.5° F above the heating setpoint, whichever produces the highest economizer control setpoint.
Example:
Heating Setpoint = 68°
Cooling Setpoint = 70°
The control temperature for the economizer will be 1.5° above the heating setpoint
due to it producing the least amount of offset.
Heating Setpoint = 55°
Cooling Setpoint = 75°
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:
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