Gas Furnace Control (Cxtq-Ta Models) - Daikin RXSQ24TAVJU Service Manual

SiUS331708EA

6.13 Gas Furnace Control (CXTQ-TA Models)

Outline When conditions for gas furnace operation are established, the system transits into the standby
mode for pre-gas furnace operation. In this status, heating operation is not performed with either
heat pump or gas furnace. Afterward when the system transits into gas furnace operation, CXTQ
requires the gas furnace combustion heating.
Detail
Thermostat ON
∗1. Time is up in factory setting.
∗2. E0, E1, E2, E7, EC, Ed are subject to the abnormality among error codes displayed on the PCB of the
gas furnace.
∗3. These conditions are not established until heat pump prohibition time elapsed after entering the
standby mode for pre-gas furnace operation (except for the case where the condition has been
established when entering the standby mode for pre-gas furnace operation).
Refer to field setting 11(21)-3 for the heat pump prohibition duration.
∗4. Refer to Gas Furnace Operation Prohibition on page 58 for details.
∗5. Refer to item 14 Switch over ambient setting on Setting Mode 2 on page 115 for details.
∗6. Refer to Gas Furnace Operation Startup Prohibition on page 58 for details.
Functions and Control
• Thermostat Step 1: ON
OR
Heat pump operation
Timer A
55 minutes timer starts.
• Hot-water heater signal (from outdoor unit): OFF
OR
• Compressor is operating
• Operation is not in heating
• Gas furnace operation prohibition signal (from outdoor unit): ON (∗4)
• Outdoor unit does not support simultaneous operation of heat pump
&
and gas furnace
OR
OR
&
• Filed setting 11(21)-3: 01, 03, 05
&
• During defrost/oil return operation
Thermostat OFF
• Hot-water heater signal (from outdoor unit): ON
&
• Compressor is suspended
• Operation mode: heating
• Gas furnace operation prohibition signal (from outdoor unit): OFF (∗4)
• Outdoor unit supports simultaneous operation of heat pump and gas
furnace
• Time of timer A is up (∗1)
&
• No error code (Ed) is displayed on PCB of gas furnace
• Thermostat Step 2: ON
• Gas furnace operation requiring signal (from outdoor unit): ON (∗5)
OR
• Field setting 11(21)-3: 07, 09, 11
&
• During defrost/oil return operation
• Gas furnace abnormality continues
for 5 minutes or more (∗2)
&
• Hot-water heater signal (from
outdoor unit): OFF
• Thermostat Step 2: OFF (∗3)
• Gas furnace operation requiring signal (from outdoor unit): OFF (∗3) (∗5)
• Not during defrost/oil return operation or preparation
Outline of Control (Indoor Unit)
• Thermostat Step 1: OFF
• CXTQ is during heat pump operation
&
OR
• Not during defrost/oil return operation
Pre-gas furnace
operation standby
• Gas furnace startup
prohibition signal
(from outdoor unit):
OFF (∗6)
Gas furnace operation
82