Hussmann proto-aire Manuel De Montage
Protocol™ Installation and
Service Manual
Liquid Injection
When operating at high compression ratios, injecting liquid partway through the
compression process is a method of cooling the scroll compressor. Hussmann applies
liquid injection on all units below 0 °F evaporating temperature. Each compressor has its
own Direct Thermal Control (DTC) valve, which is an all-in-one injection solenoid that
allows for a more energy efficient use of liquid.
Note: On units with remote air-cooled condensers, liquid refrigerant must be piped to the
liquid injection header inside the Protocol™ unit.
Vapor Injection
Another method of cooling compressors is to use vapor injection. The Protocol High
Efficiency (HE) series incorporates vapor injected (ZFKV) scroll compressors for low
temperature applications, and the ZBKCE series of scroll compressors for medium
temperature. The Protocol High Efficiency series systems are designed specifically for
R404A/R507 HFC refrigerants. When compared to the standard Protocol low temperature
unit at typical design conditions, the HE series has 40 % more capacity and has a 20%
improvement in EER. This is accomplished by the economizer cycle, which sub cools
liquid refrigerant through a heat exchanger and injects vapor via a port on the compressor
at a "mid-pocket" interstage pressure. The HE series is available in horizontal units and 3
wide vertical frame units with air or water cooled options. However when selecting
horizontal models, they MUST BE accessible from the Top. When sizing EVI Low Temp
compressors, DO NOT EXCEED 85% of capacity rating. Also Liquid Lines MUST BE
INSULATED.
Protocol HE horizontal units must be accessible from the top. The economizer system is
pre-installed on every Protocol HE unit. Factory settings for the EPR between the heat
exchanger and compressor injection ports in the system are the following:
When operating at high compression ratios, injecting liquid partway through the
compression process is a method of cooling the scroll compressor. Hussmann applies
liquid injection on all units below 0 °F evaporating temperature. Each compressor has its
own Direct Thermal Control (DTC) valve, which is an all-in-one injection solenoid that
allows for a more energy efficient use of liquid.
Note: On units with remote air-cooled condensers, liquid refrigerant must be piped to the
liquid injection header inside the Protocol™ unit.
Vapor Injection
Another method of cooling compressors is to use vapor injection. The Protocol High
Efficiency (HE) series incorporates vapor injected (ZFKV) scroll compressors for low
temperature applications, and the ZBKCE series of scroll compressors for medium
temperature. The Protocol High Efficiency series systems are designed specifically for
R404A/R507 HFC refrigerants. When compared to the standard Protocol low temperature
unit at typical design conditions, the HE series has 40 % more capacity and has a 20%
improvement in EER. This is accomplished by the economizer cycle, which sub cools
liquid refrigerant through a heat exchanger and injects vapor via a port on the compressor
at a "mid-pocket" interstage pressure. The HE series is available in horizontal units and 3
wide vertical frame units with air or water cooled options. However when selecting
horizontal models, they MUST BE accessible from the Top. When sizing EVI Low Temp
compressors, DO NOT EXCEED 85% of capacity rating. Also Liquid Lines MUST BE
INSULATED.
Protocol HE horizontal units must be accessible from the top. The economizer system is
pre-installed on every Protocol HE unit. Factory settings for the EPR between the heat
exchanger and compressor injection ports in the system are the following:
R404A
R507
77.0
psi 80
psi
However field adjustments of the EPR may be required at a later date, therefore horizontal
units must be accessible from the top.
The expansion valve in the economizer loop may also need to be adjusted once the system
is operating. Settings need to maintain approximately a 10
°F superheat after the heat
exchanger.
The subcooled liquid to the cases is designed to be approximately 50
The subcooled liquid to the cases is designed to be approximately 50
°F leaving the heat
exchanger when vapor injection is activated. When liquid temperatures entering the
subcooler fall to 55
subcooler fall to 55
°F, the T-STAT control in the unit will open and will de-energize the
solenoid ahead of the expansion valve, thus disabling vapor injection. The T-STAT control
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