Device Control System - Hitachi RAS-2-HVNP Service Manual

5. Control System

5.1 Device control system

Control subject
Control frequency of inverter
compressor
Opening degree expansion
valve of outdoor unit
Opening degree expansion
valve of indoor unit
Outdoor fan control
4-Way valve (RVR)
Solenoid valve (SVA) (Equalised
pressure valve)
Solenoid valve (SVC) (Hot gas
discharge bypass)
Solenoid Valve (SVF) (Oil return)
High/Low pressure balance
N O T E
• I.U.: Indoor unit
• O.U.: Outdoor unit
• Tc / Te: Condensing temperature / Evaporating temperature
• Td: Discharge temperature
• Tl: Liquid temperature
• Tg: Gas temperature
• Cap: Capacity
• Temp.: Temperature
118
SMGB0079 rev.0 - 01/2013
Cooling operation
The frequency control is determined
with the next parameters:
• Ratio (I.U. capacity/O.U. ca-
pacity) for individual operation.
• Temperature difference be-
tween air inlet temperature and
setting air temperature.
Fully open
• Control range of expansion
valve opening degree is deter-
mined to optimize I.U. gas pipe
temp. (Tg) - I.U. liquid pipe
temp. (Tl) difference.
• The expansion valve opening
degree is controlled according
to the number of connected I.U
for individual operation.
• Fan step is operated for O.U.
liquid pipe temp. (Te) stabiliza-
tion control.
OFF
• Turn ON at starting.
• Pd increase protection control.
RAS-(4-12)H(V)N(P/C)(E)
—
Turn ON at compressor operation
RAS-12HN(P/C)
RAS-(2-2.5)HVNP / RAS-
3HVN(P/C)(E):
Performed at the indoor expansion
valve.
RAS-(4-12)H(V)N(P/C)(E):
Turn ON SVA during stop.
Purpose
Heating operation
The frequency control is determined
with the next parameters:
• Ratio (I.U. capacity/O.U. ca-
pacity) for individual operation.
• Temperature difference be-
tween air inlet temperature and
setting air temperature.
• Control range of expansion
valve opening degree is deter-
mined to optimize temperature.
on the top of compressor.
• When number of I.U. is de-
creased, determined with I.U.
capacity. Ratio of (before/after
decrease or with above condi-
tion) for individual operation.
• Specified opening degree at
normal control starting. After-
ward, controlled to optimize
I.U. liquid pipe temp. (Tl)
• The expansion valve opening
degree is controlled according to
the number of connected I.U for
individual operation.
• Fan Step is controlled accord-
ing to O.U. liquid pipe temp.
and temp. on the top of com-
pressor.
ON
• Turn ON at starting.
• Pd increase protection control.
RAS-(4-12)H(V)N(P/C)(E)
Turn ON depending on I.U. dis-
charge / suction temperature,
outdoor temperature, outdoor liquid
temperature, etc.
RAS-(3-12)H(V)N(P/C)(E)
Turn ON at compressor operation
RAS-12HN(P/C)
RAS-(2-2.5)HVNP / RAS-
3HVN(P/C)(E):
Performed at the outdoor expan-
sion valve.
RAS-(4-12)H(V)N(P/C)(E):
Turn ON SVA during stop.
Defrost operation
Fixed frequency
(For RAS-(2-2.5)HVNP and RAS-
3HVNC: stop compressor during 30
sec. After defrosting condition was
completed)
Fully open
Specified opening degrees control-
led by temp. on the top of compres-
sor. (Td).
Fan stop.
OFF
Turn ON at starting.
RAS-(4-12)H(V)N(P/C)(E)
—
Turn ON during defrosting
RAS-12HN(P/C)
—