Control; Control Of Heat Source Unit - Mitsubishi Electric CITY MULTI PQRY-P200YMF-B Service Handbook

5 5 5 5 5 CONTROL

[1] Control of Heat Source Unit

(1) Initial processing
• When turning on power source, initial processing of microcomputer is given top priority.
• During initial processing, control processing corresponding to operation signal is suspended. The control process-
ing is resumed after initial processing is completed. (Initial processing : Data processing in microcomputer and
initial setting of each LEV opening, requiring approx. 2 minutes at the maximum.)
(2) Control at staring
• In case unit is started within 2 hours after turning on power source at low ambient temperature (+5˚C or less), the
unit does not start operating for 30 minutes at the maximum.
(3) Bypass, capacity control
• Solenoid valve consists of bypass solenoid valve (SV1, SV2) bypassing between high pressure side and low
pressure sider. The following operation will be provided.
1) Bypass solenoid valves SV1 and SV2 (both "open" when turned on)
Item
When starting compressor
After thermost "ON is returned and
after 3 minutes restart
When compressor stops in cooling or
heating mode
After operation stops
During oil recovery operations
During 20Hz operations, at fall in low
pressure
When high pressure rises (Pd)
When high pressure (Pd) rises during
20Hz operations
(3 minutes after starting)
When discharge temperature rises
(3 minutes after starting)
Compressor
Bypass
solenoid
Start
valve (SV1)
(4-minute)
(4) Frequency control
• Depending on capacity required, capacity control change and frequency change are performed to keep constant
evaporation temperature in cooling operations, and high pressure saturation temperature in heating operation.
• Frequency change is perfprmed at the rate of 2Hz/second across 20 ~ 105Hz range.
1) Frequency control starting
• 60Hz is the upper limit for 3 minutes after starting.
• 75Hz is the upper limit within 30 minutes at the first starting compressor after turning on power source.
SV1
ON (Open)
Turned on for 4 minutes
Turned on for 4 minutes
Always turned on
Turned on for 3 minutes
Always turned on.
When Pd reaches
2
27.5kg/cm G
(2.70MPa)
Thermo. Thermo.
OFF ON
(2-minute)
OFF (Close)
– When Ps is 1.5kg/
cm 2
less
When Pd reaches
When Pd is under
2 26.5kg/cm
24kg/cm G (2.35MPa)
and 30 seconds (2.60MPa)
Turned on when high
–
pressure (Pd) ex-
ceeds pressure limit
When temp. exceeds
130˚C
Stop
(3-minute)
–50–
SV2
ON (Open) OFF (Close)
–
–
–
–
Always turned on.
When Ps is 2.5kg/
G (0.15MPa) or cm 2 G (0.25MPa) or
more
When Pd is under
2 G 23.5kg/cm
(2.30MPa) and 30
seconds
When high pressure
(Pd) is 20kg/cm
(1.96MPa) or less
When discharge
temp. is 115˚C
2 G
2
G