User Manual

Sequence of Operation
Electric Heat (Optional)
13
Siemens Industry, Inc.
Application Note, App 14900
140-1231
2020-02-11
● An Inter-stage Delay timer must be enforced between the second cooling stage
OFF and the first cooling stage OFF to ensure that the first compressor will not be
turned off until the second compressor has been turned off for the time set in the
Inter-stage Delay.
If CoolStg = 3, the application controls COMPRESSOR 3 (O/B or AuxOut1) as
follows:
● If IndoorTmpEff is greater than the switching on point of the third cooling stage
(CoolingSp + 1/2 CoolingDB + StgDifCl*2), the third compressor has been OFF
for at least the time set in MIN OFF, and the Inter-stage delay timer has expired,
COMPRESSOR 3 (O/B or AuxOut1) is turned ON.
● If IndoorTempEff is less than the switching off point of the third cooling stage
(CoolingSp – 1/2 CoolingDB + StgDifCl*2), and the third compressor has been
ON for at least the time set in MIN ON, COMPRESSOR 3 (O/B or AuxOut1) is
turned OFF.
● An Inter-stage Delay timer must be enforced between the third cooling stage OFF
and the second cooling stage OFF to ensure that the second compressor will not
be turned off until the third compressor has been turned off for the time set in the
Inter-stage Delay.
Electric Heat (Optional)
When the HVAC Mode is in heating mode, and the heating staging logic controls the
electric heater, Parameter P105 (HTG FAN) in the Installer Setup Menu, Fan
Operation, FanOpr must be set to ELE.
If a heating stage has been ON, it will not shut OFF until its minimum ON timer has
expired. Likewise, if a heating stage has been OFF, it will not turn ON until its minimum
OFF timer has expired.
In addition to above rules, a time-based separation of heating stages -- Heating Inter-
stage Delay applies to the unit with multiple heating stages.
The following paragraphs explain the electric heater staging.
If HeatStg = 0, the application does not control HTG STG 1 (W1).
If HeatStg ≥ 1, the application controls HTG STG 1 (W1) as follows:
● If IndoorTmpEff is less than the switching on point of the first heating stage
(HeatingSp – 1/2 HeatingDB), and the first heating stage has been OFF for at
least the time set in MIN OFF, HTG STG 1 is turned ON.
● If IndoorTmpEff is greater than the switching off point of the first heating stage
(HeatingSp + 1/2 HeatingDB), and the first heating stage has been ON for at least
the time set in MIN ON, HTG STG 1 (W1) is turned OFF.
If HeatStg ≤ 1, the application does not control HTG STG 2 (W2).
If HeatStg ≥ 2, the application controls HTG STG 2 (W2) as follows:
● If IndoorTmpEff is less than the switching on point of the second heating stage
(HeatingSp – 1/2 HeatingDB – StgDifHt), the second heating stage has been
OFF for at least the time set in MIN OFF, and Inter-stage Delay timer has expired,
HTG STG 2 (W2) is turned ON.
● If IndoorTmpEff is greater than the switching off point of the second heating stage
(HeatingSp + 1/2 HeatingDB – StgDifHt), and the second heating stage has been
ON for at least the time set in MIN ON, HTG STG 2 (W2) is turned OFF.