Carrier Weathermaster 48P030-100 Controls, Start-Up, Operation, Service, And Troubleshooting page 243

— This is a normal cooling mode when a low cooling
demand exists.
HVAC mode:
— This is a normal cooling mode when a high
cooling demand exists.
HVAC mode:
— This is a normal heating mode when a low
heating demand exists.
HVAC mode:
— This is a normal heating mode when a high
heating demand exists.
HVAC mode:
— In this mode the unit will operate in cooling but
will be using the economizer for free cooling.
Entering this mode will depend on the status of the
outside air. The unit can be configured for outside
air changeover, differential dry bulb changeover,
outside air enthalpy
enthalpy changeover, or a custom arrangement
of enthalpy/dewpoint and dry bulb. See the
Economizer section for further details.
NOTE: There is also a transitional mode whereby the machine
may be waiting for relay timeguards to expire before shutting the
machine completely down:
HVAC mode:
APPENDIX F — MODE SELECTION PROCESS (CONT)
("High Cool ")
("Low Heat ")
("High Heat ")
("Unocc. Free Cool")
changeover, differential
("Shutting Down ")
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