Carrier TP-NHP - Manual (Page 44)

42
Ten−Minute Staging Timer
In multistage heating or cooling, this timer prevents any higher stage from
turning on until preceding stage has been on for 10 minutes. When staging
between compressor and electric heat or between compressor and furnace heat,
the time is configurable. The timer is configurable via Option 17. This timer is
overridden if temperature error is greater than 5 _ (usually due to a large change
in desired temperature) and equipment stages up in 60 second intervals.
The ten−minute staging timer does not require the thermostat to change to a
higher stage after 10 minutes. If the system is able to meet the demand (maintain
setpoint) it may not change stages after the 10 minute timer has expired. If there
is sufficient demand for a higher stage at the end of 10 minutes or at any time
after the 10 minute timer has expired, the thermostat will energize the next higher
stage.
Defrost
Detection of defrost will not work properly if the installer has configured the
O/W2/B output to function as a B output. During heat pump heating, a defrost
signal shall be considered valid if the compressor output is energized and the
defrost signal has been active for less than 15 consecutive minutes. Any defrost
signal present for longer than 15 minutes shall be considered invalid.
Heat pump/fan coil systems shall use this input to:
S Detect that defrost is in progress and energize the auxiliary heat to
provide homeowner comfort during the defrost cycle
S Allow a defrost cycle to run to completion regardless of the system
demand