Daikin BPMK928B42, Service Manual

Page: 179 / 410

System control Si18-201
166 Main Functions
3.37 4-Way Valve Operation
3.37.1 4-Way Valve Operation Security
Purpose of the
Function This function ensures proper operation of the 4-way valve. (Because the pilot-system drive
method is used, the current from the coil cannot provide fail-proof 4-way valve operation.
Therefore, the difference of pressure before and after the valve is used to ensure proper valve
operation.)
Outline Because the pilot-system drive method is used, the current from the coil cannot provide fail-
proof 4-way valve operation. Therefore, the use of the difference of pressure before and after
the valve is required. At the time of operation when the 4-way valve switches, the operating
frequency exceeding a specified frequency is output for a predetermined time duration to
ensure differential pressure necessary for the 4-way valve operation.
Details
3.37.2 4-Way Valve Switching
Outline When the outdoor heat exchanger is used as a condenser (in cooling and defrosting), the 4-way
valve is not supplied with current. When the indoor heat exchanger is used as a condenser, it is
supplied with current. To reduce the switching noise when heating operation stops (ON
→
OFF), the 4-way valve switching after heating operation shutdown is delayed.
Details The 4-way valve switching delay is 140 seconds for OFF delay.
To reduce power consumption during current flow, a OFF process is conducted when the
heating thermostat OFF time exceeds 60 minutes.
Cooling Heating
Continuing time of 4-way valve
operation 90sec 90sec
Frequency of 4-way valve operation 62Hz 41Hz