Discharge pressure transducers automatically adjust ambient coil fan speed to suit different
ambient conditions and protects the unit from over pressure. Suction pressure transducers ensure
correct suction superheat control.
The EVI does two things to enhance performance:
• The EVI uses a BPHE that subcooled liquid refrigerant stacking from the condenser passes
through on one side before reaching the main EEV.
• On the other side of the BPHE, refrigerant is metered at the inlet by the EVI’s EEV that is piped
back to the liquid line before reaching the main EEV. The leaving refrigerant metered side of the
BPHE is piped back to suction side of compressor
This process creates a pressure drop, transferring the cool gas caused by the pressure drop
flashing from liquid to vapor to the already subcooled liquid coming from the condenser, further
subcooling it. After this, the remaining cool gas returns to the compressor allowing for a wider
envelope of compressor motor cooling and lower discharge superheat, especially during low load
conditions when cool suction return gas would otherwise be insufficient.
Heat exchanger
The compact, high-efficiency brazed plate heat exchanger (BPHE) is constructed with 316L stainless
steel corrugated channel plates with a filler material between each plate. Units with two refrigerant
systems use dual circuit BPHEs.
The refrigerant-side design working pressure of the heat exchanger is 725 psi (50 bar) and the
waterside, or piping, design working pressure is 334 psi (23 bar).
BPHE inlet and outlet connections are grooved for compatibility with standard Victaulic
connections. A 30-mesh wye-strainer is provided as standard for installation upstream of the BPHE
to prevent clogging from liquid system debris, particularly at system start-up when construction
debris may be present in the piping system.
The BPHE is equipped with a thermostat-controlled heater for freeze protection within the
operational evelope and insulated with 3/4 in. (19 mm) flexible, closed-cell foam.
The flow switch is a standard offering for each module, installed in a pipe section at the outlet of
the BPHE.
Ambient coils
Coils: Fin and tube coils of seamless, internally-enhanced, high-condensing-coefficient, corrosion
resistant copper tubes are arranged in staggered rows, mechanically expanded into hydrophilic
aluminum fins. The designed working pressure of the coil is 650 psig (45 bar).
Fans: The ambient fans are composed of corrosion-resistant aluminum blades sprayed with PP
plastic and galvanized sheet steel fan housing coated with black plastic. They are designed for
maximum efficiency with integrated VSD. All blades are statically and dynamically balanced for
vibration-free operation. The fan grilles are constructed of heavy-gauge, rust-resistant, coated
steel.
EC motors: The fans are directly driven by electrical commutation (EC) motors. Fan speed is
controlled through Modbus® communication.
YMAE Air-Cooled Inverter Scroll Chiller and Heat Pump18
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