Controlling The Outdoor Unit - Mitsubishi Electric PUHY-P200 Service Handbook

[2] Controlling the Outdoor Unit

1. Initial control
• When the power is turned on, the initial processing of the microcomputer is given top priority.
• During the initial processing, control processing of the operation signal is suspended. The control processing is
resumed after the initial processing is completed.
(Initial processing: processing of the data inside the microcomputer and initial setting of each LEV opening,
requiring up to approximately 2 minutes.)
• During the initial processing, the LED monitor on the outdoor unit's main board displays "S/W version", "refrig-
erant type", "heat pump", "cooling only and capacity" in turn every second.
2. Control at start-up
• The upper limit of frequency during the first 3 minutes of the operation is 50Hz.
• When 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 (P200-P400: SV1, P450-P650: SV1, SV3), which bypass the high- and low- pressure
sides, operate in the following manner.
(1) Bypass solenoid valve (SV1) (ON = Open)
Operation Timing
At No. 1 compressor start up
or at No. 2 compressor start up
(P450-P650 types only)
After the restoration of thermo
or 3 minutes after restart
During cooling or heating operation
with the compressor stopped
After the operation has stopped
During defrost operation
(See figure ✻1 below)
During oil-recovery operation
During an operation with the
compressor running at 30Hz
When low pressure (LPS) drops
(After 3 minutes have past since
start up)
When high pressure (Pd) rises
[ Example of an SV1 operation ]
Compressor
Bypass solenoid
valve (SV1)
(4-minute)
(2) Bypass Valve (SV3, P450-P650 types only) (ON = Open)
• The opening SV3 is controlled by the
configuration of No.1 and No.2 compressor
operations.
Always ON. (Exception : OFF when HPS-LPS
ON for 3 minutes. (Exception : OFF when HPS
Always OFF during cooling operation and always ON
during heating operation when running an oil-recovery operation after running a
When low pressure (LPS) drops
below 0.23 MPa.
When Pd exceeds 3.77 MPa
Start Thermo. Thermo.
up
OFF ON
(2-minute)
SV1
ON (Open)
ON for 4 minutes
ON for 2 minutes
Always ON
continuous operation at low frequency.
When low pressure (LPS) exceeds
0.38 MPa.
When Pd is or below 3.43MPa and
30 seconds has passed
Defros-
ting
Time
(8-minute)
No.1 Compressor No.2 Compressor
Stopped
In operation
In operation
- 69 -
OFF (Close)
0.2MPa)
0.2MPa)
Stop
)
(3-minute
SV3
Stopped OFF
Stopped ON
In operation OFF