Aprilaire 8551 User Manual
Page 16
Optional Settings For
Additional Thermostat Features
The Model 8551 thermostat is equipped with 2 DIP switches located inside the thermostat on the
printed circuit board. These switches are preset by the factory to typical home air conditioning system
requirements. The installing contractor also reviewed the settings during installation to be sure the
thermostat will operate properly with your air conditioning system.
The DIP switches can however be changed to customize the thermostat’s operation to your particular
needs. This should only be done after consulting with your contractor.
The Model 8551 DIP switches control the following functions:
No. 1 – 4 min. / 2 min. Minimum Equipment On / Off Times. This switch is factory preset at 2 minutes.
This switch provides short cycle protection for the air conditioning unit. If you feel that the air
conditioning system turns on and off too many times per hour, ask your contractor about changing
the switch to a 4 minute minimum on time. Keep in mind however that this may increase the
overall temperature variation in the house due to longer run and off times. DO NOT change the
position of this switch without first consulting with your contractor.
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