Hitachi RAS-4-HNCE - Device Control System

5. Control System
118
SMGB0079 rev.0 - 01/2013
5.1 Device control system
Control subject
Purpose
Cooling operation Heating operation Defrost operation
Control frequency of inverter
compressor
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.
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.
Fixed frequency
(For RAS-(2-2.5)HVNP and RAS-
3HVNC: stop compressor during 30
sec. After defrosting condition was
completed)
Opening degree expansion
valve of outdoor unit
Fully open
• 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.
Fully open
Opening degree expansion
valve of indoor unit
• 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.
• Specied 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.
Specied opening degrees control-
led by temp. on the top of compres-
sor. (Td).
Outdoor fan control
• Fan step is operated for O.U.
liquid pipe temp. (Te) stabiliza-
tion control.
• Fan Step is controlled accord-
ing to O.U. liquid pipe temp.
and temp. on the top of com-
pressor.
Fan stop.
4-Way valve (RVR) OFF ON OFF
Solenoid valve (SVA) (Equalised
pressure valve)
• Turn ON at starting.
• Pd increase protection control.
RAS-(4-12)H(V)N(P/C)(E)
• Turn ON at starting.
• Pd increase protection control.
RAS-(4-12)H(V)N(P/C)(E)
Turn ON at starting.
RAS-(4-12)H(V)N(P/C)(E)
Solenoid valve (SVC) (Hot gas
discharge bypass)
—
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)
—
Solenoid Valve (SVF) (Oil return)
Turn ON at compressor operation
RAS-12HN(P/C)
Turn ON at compressor operation
RAS-12HN(P/C)
Turn ON during defrosting
RAS-12HN(P/C)
High/Low pressure balance
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.
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.
—
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