Mitsubishi Electric CITY MULTI PUHY-P400YEM-A Service Handbook page 131

2) SV2, 3 (Full-load / Un-load switching valve) PUHN-P-YEM-A only
1
It starts in un-load in the initial start mode and during defrosting, and starts in full-load at all other times.
2
It is possible to determine whether or not the compressors are switching from unload to full load by check the changes
in amperage of the compressor at the moment of switching. The amperage under full load will be approximately 30 to
40 % more than operation under unload.
Note: The solenoid valve for SV2 is closed when conducting electricity while the SV3 is open when conducting elec-
tricity.
3) SV4 (Bypass Solenoid Valve)
This solenoid valve opens when conductive (relay ON).
Operations can be confirmed by the LED display and the operating sound.
Solenoid valve switches in the operation mode can be confirmed by the temperature of the solenoid valve outflow
circuit, and the refrigerant sound.
When the valve is open, hot gas will flow through the pipe, so do not check it by touching.
4) SV5b (Liquid Distribution Pipe Solenoid Valve)
This solenoid valve opens when conductive (relay ON).
It is possible to confirm operation by monitoring the LED display and listening to the operating sound.
(operation conditions: when the constant capacity unit is heating or performing liquid refrigerant correction control
mode)
It is possible to confirm operation switches made by solenoid valve operation by the refrigerant sound or the tem-
perature of the solenoid valve outflow circuit.
(3) Outdoor Unit Fan
1) Variable Capacity Unit
• Since the fan for the outdoor unit is controlled by phase control, check the fan speed by monitoring the output status
of the phase control output on the LED display. At full speed, the fan revolves at approx. 600 rev/min.
• The fan will take 5 seconds to reach full speed when starting from a stop.
• Because the variable capacity unit has two fans, it may take 10 seconds for them to reach full speed.
• On the variable capacity unit, the fan on the right is usually operated, with the left fan only being used in case of
demand. (When heating, both fans are used except for during defrosting operations).
• When the LED No. 70 FANCON output reads 100 %, the fan stops. At 0 % it will run at full speed.
• The fan speed may be modified by control.
• When a fan does not move, or produces irregular vibrations, this could be a triac problem, or the fan motor in open
phase or reverse phase operation. (Open phase or reverse phase irregularities in the main power source will be
detected by the MAIN board. However, these problems could result from the replacement of damaged fan-motor
leads during a service check.)
• When only one fan is operating, after checking the 52F output on the LED monitor, check for mis-aligned fan
connectors, mis-aligned 52F connectors, or a possible break in a lead line.
2) Constant Capacity Unit
• Fan operation is almost identical to that in the variable capacity unit, with the following differences:
• The fan will operate while the constant capacity unit No.3 compressor is operating.
• Even when the No.3 compressor is stopped, the fan will sometimes be operated to prevent refrigerant from
pooling in the heat exchanger
• The fan will run for a maximum of 15 minutes after the No.3 compressor has stopped.
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