40
Rooftop Dedicated Outdoor
Air System Installation Manual
Due to our policy of continuous product innovation, some specifications may change without notification.
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Compressor Staging (For DOAS Units with Multiple Compressors)
Cooling Mode
Dehumidification Mode (For Units Equipped with a Hot Gas Reheat Coil)
Circuit
Circuit B; Circuit A If Needed
Circuit A; Circuit B If Needed
Physical Compressor Labels
Two (2); One (1) If Needed
One (1); Two (2) If Needed
Controls Compressor Labels
One (1); Two (2) If Needed
Two (2); One (1) If Needed
Table 18: Compressor Staging for Units with Two (2) Compressors.
Table 19: Compressor Staging for Units with Four (4) Compressors.
Cooling Mode
Dehumidification Mode (For Units Equipped with a Hot Gas Reheat Coil)
Circuit
Circuit B; Circuit A If Needed
Circuit A; Circuit B If Needed
Physical Compressor Labels
Three (3) and Four (4);
One (1) and Two (2) If Needed
One (1) and Two (2); Three (3) and Four (4) If Needed
Controls Compressor Labels
One (1) and Two (2);
Three (3) and Four (4) If Needed
Three (3) and Four (4); One (1) and Two (2) If Needed
REFRIGERATION SYSTEM STARTUP
Cooling Mode
– The Digital Scroll compressor (Circuit B) will engage to maintain cooling demand. If more cooling is needed than the Digital
Scroll compressor can provide, the Standard Scroll compressor (Circuit A) will engage and the Digital Scroll compressor (Circuit B) will modu-
late to maintain the desired supply air temperature.
Dehumidification Mode
– For units equipped with a hot gas reheat coil, the Standard Scroll compressor (Circuit A) will run to lower the
DX coil temperature to the direct expansion (DX) coil set-point and modulate the hot gas reheat (HGRH) valve to maintain the supply air
temperature. If more capacity is needed to decrease the DX coil temperature to the set-point, the Digital Scroll compressor (Circuit B) will
engage to meet the set-point. The hot gas reheat valve will continue to modulate as needed to maintain the supply air temperature.
Digital Scroll Compressor Controllers
Figure 49: Digital Scroll Controllers.