Carrier 40VM Series Service Manual

Also see for 40VM Series: Installation and operating instructions Installation and operating instructions Installation and operating instructions Installation and operating instructions

Contents

22DRY CONTACTThe interface in the main board of the indoor unit is a dry contact board that can output up to four signals.Fig. 34 —Dry Contact Board• Dry contact 1-FAN is used to turn on the exhaust fan. Standard configuration is closed.Closed Condition: The dry contact is set valid from the remote controller and the fan is turned on.Open Condition: The fan is turned off or the dry contact is set invalid by the remote controller.• Dry contact 2-CTON is used to bring in fresh air when the outside air temperature is lower than the inside temperature aseconomizer is connected. Standard configuration is closed.Closed Condition: The dry contact is set to valid from the remote controller and the cooling thermo-ON.Open Condition: Cooling thermo-OFF or dry contact is set to invalid by remote controller.• Dry contact 3-HTON is used to humidify the room air when a humidifier is installed. Standard configuration is closed.Closed Condition: The dry contact is set valid from the remote controller and heating thermo-ON.Open Condition: Heating thermo-OFF or the dry contact is set invalid by the remote controller.• Dry contact 4-AUXH is used to turn on the auxiliary heat source.NOTE: Dry contact 4-AUXH is only suitable for indoor units except the 40VMA series.1. The dry contact 4 closes while all the following requirements are met:• The indoor unit conducts heating mode or heating operation in auto mode.• The return air temperature T1 is lower than the setting temperature, Ts (Ts - T1 = 1°F/2°F/3°F/4°F/5°F). This can be set bythe remote controller. The default setting is 3°F.• The indoor unit is in operation.• The ambient temperature T4 transferred from the outdoor unit is 1.8°F lower than the auxiliary heat source turning on thetemperature set at the outdoor unit.• The dry contact function is enabled on the wired controller.2. The dry contact 4 disconnects when any of the following requirements are met:• The operation mode of the indoor unit is not heating.• The indoor unit is not in operation.• T4 transferred from the outdoor unit is higher than the auxiliary heat source turning on the temperature.• The dry contact function is prohibited from the wired controller.• Heating thermo-OFF.3. The dry contact 4 conducts time-delayed close while any of the following requirements are met:• The thermostat conducts the heating operation for the first time.• The setting temperature for the room rises and the ΔTs is larger than 3°F.• Delay time can be adjusted by wired controller (15 minutes, 30 minutes, and 45 minutes). Factory setting is 15 minutes.4. The control logic of dry contact 4:Dry contact 4 can be set to Enabled or Disabled with the wired controller. The fan on the indoor unit can be set to ON. If thefan is set to ON, it runs at setting speed when dry contact 4 closes. Otherwise, it is Normal.