Page 51
XP25
Unit Sequence of Operations
The following figures illustrate the overall unit sequence of operation along with the operation of various pressure switches and
temperature sensors. The figures also illustrate the use of the compressor anti-short-cycle function in relation to unit Status,
unit Fault and lock out LED Codes and unit system operation interactions.
No
On 24 VAC power-up or outdoor reset, the outdoor control shall perform the follow
ing tasks:
1.
Start the anti-short cycle 3-minute delay in the outdoor control.
2.
Check status of the temperature sensor and pressure devices.
3.
If the outdoor control does not detect any error codes, outdoor control sends 24 volts
out on the CNTCTR terminals to pull in the contactor coil.
(
Note
- These checks take about 60 seconds.
)
4.
The contactor contacts pull IN and main power is applied to the compressor inverter.
System
Idle
Room
Thermostat
Demand
Heating or
Cooling
All
switches
closed and
sensors in
operating
range?
Heating
Cooling
No
Yes
No
Yes
Yes
Yes
No
Below Low
BP
Above the Low BP
or Not Applicable
Emer
gency
Heat Se
lected?
Go To Auxiliary
Heating
Balance
Point
Region
Go To Primary
Heat Pump
Heating
Go To
Modulat
ing Heat
Pump
Heat
Go To
Modu
lating
Cooling
All
switches
closed and
sensors in
operating
range?
Check for status or
fault codes in outdoor
control or room ther
mostat (Note - Refer to
low pressure and high
pressure switch flow
charts for sequence of
operation).
Figure 29.
24 VAC Power-Up or Outdoor Reset
