User Manual

Sequence of Operation
Ambient Heat Pump Lockouts
16
Siemens Industry, Inc.
Application Note, App 14901
140-1230
2020-02-11
Figure 4: Ambient Heat Pump Lockouts.
● If Parameter P105 (HTG FAN) FanOpr = gAS, then Parameter P206 (HP COMP
LO) HPCompLock is not visible, and Parameter P207 (HP AUX LO) HpAuxLock
is defined as the balance point. If the outdoor temperature is above P207, the
compressor operates exclusively. If the outdoor temperature is below P207,
auxiliary heat operates exclusively.
● There must be at least 5°F deadband between the Compressor Lockout SP and
the Auxiliary Heat Lockout SP. When one setpoint changes, the other may also
change to maintain the 5°F deadband.
● A 10-minute confirmation timer is enforced when in enter/exit lockout. In
trigger/perish lockout, dropping multiple stages is allowed (with a tiny separation
timer), an Inter-stage Delay timer must be enforced for rising multiple stages.
● If the unit starts when compressors have been locked out, auxiliary heat stages
ascend to fill the vacancy left by the compressors. For example, when compressor
lockout (Parameter P206 [HP COMP LO]) occurs, Aux1 and Aux2 should be
treated as Stage1 and Stage 2 Heat.