Siemens 125-1957 - Manual (Page 18)

APOGEE Unit Vent Controller
⎯
0 to 10 V Output Owner’s Manual
8 Siemens Building Technologies. Inc.
Cooling Loop – maintains room temperature setpoint by turning valves on and off and using
free cooling (mixed air control) when available.
Auxiliary Loop – modulates the auxiliary loop using the auxiliary setpoint and discharge
setpoint (2284).
Mixed Air Loop – modulates the mixed air loop using the mixed air setpoint and mixed air
temperature (2283).
DX Loop – modulates the cooling loop using the control setpoint and room temperature
(2284).
Morning Warm-up/Cool-down
Morning warm-up or cool-down occurs after the controller switches from night mode to day
mode, upon power-up, or if the controller is reset. During morning warm-up or cool-down, the
controller provides maximum heating or cooling with the outdoor air damper closed until the
temperature of the space reaches setpoint.
ON/OFF Coil Valve Control
When a face-bypass configuration is used, the coils may be turned on and off with two-
position valves using DOs.
Electric Heat
If electric heat is used, it is controlled as follows:
HTG OUTPUT
(Point 60)
Stage 1 Stage 2 Stage 3
0% to 33% ON OFF OFF
34% to 66% ON ON OFF
67% to 100% ON ON ON
In addition, no stage may turn on or off until the time delay has elapsed. Stage one will
always be the first stage to turn on and the last stage to turn off.
Fan Operation
Day Mode – The fan is on all the time.
Night Mode – The fan only operates when required for heating or cooling.
Fail-safe Operation
A low temperature detection thermostat (LTDT) can be used to signal the controller when the
temperature drops below the low temperature limit.