Form CP-MAPS-D12 with FX05, Page 8
After the rst 180 seconds from the 1st stage activating, if the discharge air
temperature does not increase above ½ of the band (HPP), the controller will
turn on the 2nd stage. The 2nd stage closes (DO-3), and the 1st stage (DO-2)
remains ON for 20 seconds. The system uses the 1st stage to ignite the 2nd
stage and vice versa. After twenty seconds, stage 1 will turn OFF.
The 2nd stage has a minimum run time of 100 seconds. If the discharge air
temperature is still less than 1/2 of HPP after 100 seconds, then the system will
activate the 3rd stage. Stage 3 heating is stage 1 and 2 combined (DO-2 and
DO-3 closed), providing 100% heating.
If the discharge air temperature increases above 75ºF, then the stages start
turning OFF in the reverse sequence. If the dAt remains between the propor-
tional band (HPP = 10, 65ºF to 75ºF), the unit will not add or subtract a stage
of heating. Stage 3 does not have a minimum run time.
For optional modulating gas heat units, the same sequence applies with the
following addition. When the unit is in any stage of heating other than OFF, the
gas modulating value will vary from 100% open to 50% open based upon the
heating discharge air proportional band (HPP).
Example: If the discharge air temperature (dAt) is 4.9ºF above the setpoint,
AO-1 output will provide 50% gas. If the dAt is 4.9ºF below the setpoint, the
gas value will modulate to provide 100% gas. When heating is not required,
the analog output will be 10V, 50% open. (The gas valve converts the con-
trol signal voltage: 10V - 0V = signal at the valve = 3 VDC = 100% open, 7
VDC = 50% open).
Heating Mode Lockout
If the Discharge Air Temperature (Point AI-4), does not rise above LSP (36ºF)
in 600 seconds after blower enables, the unit will shut down. Upon a rise in
discharge air temperature (LSP + 30ºF = 66ºF), the unit is enabled. Three
consecutive lockouts within one hour will result in a continuous lockout state
(24 VAC power must be cycled to reset the controller). If the Outdoor Air Tem-
perature sensor fails, the blower will operate without cooling, reheat, or heating
equipment active. If the Outdoor Air Temperature rises above the oH1 heating
lockout (62ºF), the heating equipment will be turned OFF after the minimum
run times.
Heating Mode
(cont’d)
Heating and
Cooling Control
Modes (cont’d)
Heat Staging (cont’d)
Cooling Mode
When the unit is in cooling mode, the unit will discharge air based upon the
neutral air cooling setpoint point (dCH) and the room discharge air cooling set-
point (rCP). If the space sensor is not installed, the unit will operate to provide
neutral air only.
If a space sensor is installed, the unit will change from the neutral discharge
air temperature setpoint to the room discharge air heating setpoint (rCP) value
whenever the space requires cooling. Whenever the space temperature is
above the setpoint by a value greater than the space cooling proportional band
(SCP), the space will call for space cooling to be ON. The SCP default value
is 1.8ºF.
Example:
Space cooling setpoint SSP = 75°F (Default)
Space cooling proportional band (SCP) = 1.8ºF (adjustable 1 to 8ºF)
Space cooling active above: (SSP + SCP) = 75ºF + 1.8ºF = 76.8ºF
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