Orion System RNE Modular Controller - Manual (Page 65)

RNE Modular Controller Field Technical Guide
SEQUENCE OF OPERATION
65
Outdoor Air Lockouts
The Outdoor Air Cooling and Heating Lockouts Setpoints are designed
to prevent unwanted Mechanical Heating or Cooling operation during
certain Outdoor Ambient Temperature conditions.
When the Outdoor Air Temperature is below the Cooling Lockout
Setpoint, no Mechanical Cooling can operate. However, if the unit is
equipped with an Economizer and the RNE is confi gured to use the
Economizer, it can be used to provide free Cooling when the Mechani-
cal Cooling is locked out. For Heat Pumps, the Cooling Lockout also
applies to Compressor Heating, which means it usually will be a lower
setting than on Cooling units that are not Heat Pumps.
The Outdoor Air Heating Lockout operates so that when the Outdoor
Air Temperature is above the Outdoor Air Heating Lockout Setpoints,
no Mechanical Heating can operate. This applies to any type of Heating
except Compressor Heating as used on Heat Pumps. The lockout for
Compressor Heating is explained in the previous paragraph regarding
Cooling Lockout Setpoints.
Outdoor Air Lockouts & Supply Air Cutoffs
Supply Air Cutoffs
The Supply Air Temperature Cutoffs are designed to prevent extremely
High and Low Temperature Supply Air from entering the building.
High Supply Air Temperature Cutoff
High Supply Air Temperature Cutoff is initiated when the Supply Air
Temperature rises above the HI SAT Cutoff Setpoint. When this occurs,
Heating stages will be deactivated until the Supply Air Temperature falls
5°F below the HI SAT Cutoff Setpoint. Also, the Outside Air Damper
will move to its Minimum Economizer Position.
Low Supply Air Temperature Cutoff
Low Supply Air Temperature Cutoff is initiated when the Supply Air
Temperature falls below the LO SAT Cutoff Setpoint. If the RNE is in
Economizer Operation, Vent Mode, or Heating Mode and the Supply
Air Temperature falls below the LO SAT Cutoff Setpoint for 10 minutes,
it is assumed a Mechanical Failure has occurred and all Heating will
be deactivated, the Supply Air Fan will shut off, and the Outdoor Air
Dampers will close. If the RNE is in the Cooling or Dehumidifi cation
Mode and the Supply Air Temperature falls below the LO SAT Cutoff
Setpoint, the Cooling Signal or Cooling Stages will immediately begin
deactivating.
To restore normal operation, one of the following three things must occur:
1. The Supply Air Temperature rises above the LO SAT
Cutoff Setpoint by 5°F.
2. The RNE goes from Occupied to Unoccupied or
from Unoccupied to Occupied Mode.
3. The RNE’s power is cycled.