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

Ideal/Perfect Defrost Infinity/Evolution Set as Default in UI

DEFROST TIME NEXT DEFROST INTERVAL

< 3 minutes 120 minutes

3 to 5 minutes 90 minutes

5 to 7 minutes 60 minutes

> 7 minutes 30 minutes

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

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

• 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

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

Time Delays

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

• Begins 20 min after defrost termination

• Ignored during low ambient cooling

• Ignored until unit as run for 5 consecutive minutes

Outdoor Thermistors Comparison

• If the outdoor thermistor indicates

30F warmer than the coil thermistor

OR• If the outdoor thermistor indicates

10F cooler than the coil thermistor

Outdoor Thermistors ComparisonRange Error – Heating Might Change

• If the outdoor thermistor indicates 10F warmer than the coil thermistor

OR• If the outdoor thermistor indicates 20F

cooler than the coil thermistor`

Outdoor Thermistors ComparisonRange Error – Cooling

MIGHT CHANGE

Thermistor Failure Default OperationFAILED COMPONENT FUNCTION

DEFAULT OPERATION

Low Ambient Cooling

No function

Defrost Inhibit

Defrost will be initiated based on

coil temperature and time

One minute fan off delay on COOL

mode

No delay functions if failure is open or short. Continue

function for a thermistor range

error.

Defrost Initiate and Terminate

Defrost will occur at each time interval, but will terminate

after 5 minutesLow

Ambient Cooling

No function

Outdoor Sensor (OAT)

Coil Sensor (OCT)