Mitsubishi Electric PU(H)Y-P250YGM-A, Service Handbook

Page: 89 / 215

- 80 -
[
VII
Control ]
[2] Controlling the Outdoor Unit
-1- Initial Control
ΠWhen the power is turned on, the initial processing of the microcomputer is given top priority.
ΠDuring the initial processing, control processing of the operation signal is suspended. The control processing is resumed
after the initial processing is completed. (Initial processing involves data processing in the microcomputer and initial setting
of each of the LEV opening. This process will take up to 1 minute.)
ΠDuring the initial processing, the LED monitor on the outdoor unit's main board displays S/W version -> refrigerant type
-> model and capacity -> and communication address in turn every second.
-2- Control at Start-up
ΠThe upper limit of frequency during the first 3 minutes of the operation is 50 Hz.
ΠWhen the power is turned on, normal operation will start after the initial start-up mode (to be described later) has been
completed (with a restriction on the frequency).
-3- Bypass Control
Bypass solenoid valves (P250,SV1; P500,SV1,SV3), which bypass the high- and low- pressure sides, perform the follow-
ing functions.
(1) Bypass solenoid valve (SV1) (ON = Open)
[Example of an SV1 operation]
(2) Bypass valve (SV3, P500 model only) (ON = Open)
The opening of SV3 is controlled by the operating state of No.1 and No.2 compressors.
Operation
SV1
ON OFF
At No. 1 compressor start-up or at No. 2
compressor start-up
(P500 model only) ON for 4 minutes.
After the restoration of thermo or 3 minutes
after restart ON for 2 minutes.
During cooling or heating operation with the
compressor stopped Always ON.
Exception: OFF when HPS-LPS is 0.2 MPa or less
After the operation has stopped ON for 3 minutes.
Exception: OFF when HPS-LPS is 0.2 MPa or less
During defrost operation
(See *1 in the figure below.) Always ON
During oil-recovery operation Always OFF during cooling operation and always ON during heating op-
eration when running an oil-recovery operation after running a continuous
operation at low frequency.
During an operation with the compressor
running at 30 Hz (After 3 minutes have
passed since start-up) When low pressure (LPS) drops
below 0.23 MPa. When low pressure (LPS) exceeds
0.38 MPa.
When high pressure (Pd) rises When Pd exceeds
3.77 MPa When Pd is or below
3.43 MPa and 30 seconds have
passed
No.1 Compressor No.2 Compressor SV3
Stopped Stopped OFF
In operation Stopped ON
In operation In operation OFF
Start-
up
Thermo. Thermo. Defrost
time
(*1)
Stopped
OFF ON
Compressor
Bypass solenoid
valve (SV1)
(4-min.) (2-min.) (8-min.) (3-min.
)