Sequence of Operation

The improved Building #4 HVAC system consists essentially of the following components:

• Original equipment:


• Three subfloor air handlers (SAHUs), provided with an electric heating coil, chilled water cooling coil, and 100% OSA capable economizer.
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• New equipment:


• Dedicated outdoor air system (DOAS), consisting of a dual enthalpy-wheel heat recovery unit, with instantaneous steam generation humidification and DX cooling dehumidification capability.
  

Two separate and distinct sequences of operation are implemented for the Building #4 HVAC system:

1. Temperature Priority Control Mode (TPCM), and
2. Humidity Priority Control Mode (HPCM)
   

The justification for two separate control modes is economic; HPCM will be operationally more costly than TPCM.

TPCM and HPCM Are mutually exclusive; the Building #4 HVAC system shall run in either one mode or the other. The operational mode, TPCM or HPCM, will be selected via the JCI Web interface by Pacific Science Center technicians based on environmental requirements of the current exhibit. Once selected, TPCM or HPCM shall continue to run indefinitely until manually commanded otherwise via the JCI Web interface by Pacific Science Center technicians.

TEMPERATURE PRIORITY CONTROL MODE

General

In TPCM, the DOAS will run only when the building is occupied.

In TPCM, the humidity control band setpoints of the DOAS are reset to dewpoint of 60°F dp and 37 °F dp, corresponding to relative humidities of 70% and 30%, respectively, at 70°F dry-bulb temperature.

For most operational hours in this mode, the mechanical humidification and dehumidification equipment will not be energized. The exception is the coldest winter months, where the humidifier may be called upon to provide moisture for comfort conditioning. The minimal humidification setpoint of 30% is suggested initially to permit comparison with no mechanical humidification, which is the current condition for the remainder of the campus.

Subfloor air handlers shall run when occupied, and OSA/exhaust dampers shall respond in economizer mode, when occupied.

Status Messages, Warnings & Alarms

• Status Messages
  
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• Warnings
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• Alarms
  
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HUMIDITY PRIORITY CONTROL MODE

General

In HPCM, the following equipment operational states shall be in effect:

1. The DOAS and SAHUs shall run continuously, 24 hours per day.
   
2. The subfloor OSA and exhaust dampers shall be closed, and
   
3. The recirculation damper shall be 100% open.

The DOAS shall control humdity to the space sensor designated as the "lead sensor".

Status Messages, Warnings & Alarms

• Status Messages
  
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• Warnings
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• Alarms
  
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