Master-Slave Unit Eevs - LG MULTI V ARUN072BTE4 Service Manual

BASIC CONTROLS

Master-Slave Unit EEVs

Master and Slave Outdoor Unit EEV Control
Main EEV Control
Main EEV operates with fuzzy logic to keep the degree of superheat (about 37°F) at the evaporator outlet stable during heating mode.
Degree of Superheat = Tsuction - Tevaporation
where,
• Tsuction = Temperature measured at the suction pipe sensor (°F).
• Tevaporation = Evaporation temperature equivalent to low pressure (°F).
Subcooling EEV Control
Subcooling EEV operates with fuzzy logic to keep the degree of subcool (about 59°F) at the subcooler outlet stable during cooling mode.
Degree of Subcool = Tcondensation - Tliquid
where,
• Tliquid = Temperature at the outlet of the subcooler (°F).
• Tcondensation = Condensation temperature equivalent to high pressure (°F).
Avoiding Excessively High Discharge Temperatures
After the main EEV opens to a predetermined amount (R410A: 800 pulses), and the discharge temperature is above 185°F (or 85°C) during
heating mode, subcooling EEV control may operate to maintain compressor superheat.
Vapor Injection Flow Rate Control During Heating Mode
The degree of Superheat (VI_SH) = Subcooler out (°F) – Subcooler in (°F)
where
• Td ≤ 176°F : VI_SH = 37°F
• 176°F < Td ≤ 194°F : VI_SH = -2 × Td/10 +19
• 194°F < Td : VI_SH = 34°F
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