2-Stage Heat Pump Defrost Options

1
2-Stage Heat Pump Defrost Options

• Defrost options
• 30, 60, 90, 120 or Auto (Infinity/Evolution only)
• Defrost initiate temp 32 F
• Defrost terminate temp 65 F
• Lower defrost noise
• Normal defrost only occurs below 50 F outdoor
  temperature

2
Ideal/Perfect Defrost Infinity/Evolution Set as
Default in UI
3
2- Stage Heat Pump Forced Defrost

• Forced defrost pins provided on board
• Command also available at User Interface
• Short pins for 5 sec and release or UI command
• If coil temp is below initiate and outdoor temp
  is below 50 full defrost cycle
• If coil temp is above initiate temp OR outdoor
  temp is above 50 30 second defrost cycle occurs

4
Time Delays

• One minute off between stages Bristol only
• 5 minute mandatory high Stage on power up or 12
  hours of standby Bristol only
• Auxiliary heat remains energized for 15 seconds
  after defrost completion

5
Time Delays

• 20 second outdoor fan delay after defrost
• Reduces fog effect
• 1 minute delay in cooling mode before turning
  outdoor fan off if outdoor temp is 100 deg F or
  higher
• For easier starting

6
Time Delays

• 2 minute to return to standby from last valid
  communication
• 5-minute time guard between compressor cycles
• Can be defeated by shorting forced defrost pins
  for 1 second and releasing
• Can also be sped up by pressing fan and temp up
  together

7
Outdoor Thermistors Verification

• Considered open if resistance is reads 500K Ohms
  or higher (-50ºF or below)
• Considered shorted if resistance reads 1K ohms Or
  lower (188ºF or higher)
• Coil and Outdoor temp thermistors are compared to
  verify proper range
• If thermistors are failed, system reverts to
  default operation

8
Outdoor Thermistors Comparison

• Begins 20 min after defrost termination
• Ignored during low ambient cooling
• Ignored until unit as run for 5 consecutive
  minutes

9
Outdoor Thermistors ComparisonRange Error
Heating Might Change

• If the outdoor thermistor indicates
• ? 30?F warmer than the coil thermistor
• OR
• If the outdoor thermistor indicates ? 10?F cooler
  than the coil thermistor

10
Outdoor Thermistors ComparisonRange Error
CoolingMIGHT CHANGE

• If the outdoor thermistor indicates ? 10?F warmer
  than the coil thermistor
• OR
• If the outdoor thermistor indicates ? 20?F cooler
  than the coil thermistor

11
Thermistor Failure Default Operation