User's Manual

33
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
SW17. 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
When defrost occurs in a Hybrid Heat system, the furnace will operate during the defrost cycle.
At the end of the defrost cycle, the furnace and heat pump will be de-energized while the fan is
energized for 2 minutes allowing the heat exchanger to cool down. If SW34, Hybrid Heat
Furnace Latch is set to Off, at the end of the 2 minute time, the heat pump will be re-energized if
a call for heat still exists. If SW34 is set to On (default), the furnace will remain on until the end
of the heating cycle.
Defrost detection is not available 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 and Hybrid Heat systems shall use this input to:
 Detect that defrost is in progress and energize the auxiliary heat to provide homeowner
comfort during the defrost cycle
 Allow a defrost cycle to run to completion regardless of the system demand
Three--Minute Minimum on Time
In normal operation, when a stage turns on, it will not turn off for a minimum of 3 minutes. In
Hybrid Heat systems, the minimum on time for the furnace is 5 minutes. If the setpoint is
changed, this timer is canceled, allowing the equipment to turn off immediately when the
demand is removed. The 3 minute minimum on timer applies to all stages of heating and cooling,
except Hybrid Heat. A stage will run for a minimum of 3 minutes before the thermostat will be
allowed to stage to a lower stage.
Heat/Cool Setpoints (Desired Temperature)
A minimum difference of 1 and maximum of 6 is enforced between heating and cooling
desired temperatures. This is done by allowing 1 setting to “push” the other, to maintain this
difference. This difference is adjustable via Configuration SW11.
Equipment On Indicators
When cooling equipment is on, a COOL icon is displayed. While cooling equipment operation is
delayed by the time guard or cycle timer, COOL will flash. The same is true for HEAT icon.