Parallel Fan Powered Box

A parallel fan powered box has a fan that runs only during the heating mode to pull warm return air from the ceiling plenum.

Required Objects

The Parallel Fan Powered Box (PFPB) must have the following properties.

• It must be attached to an air system.
• It must be attached to a conditioned zone.

Design Assumptions

The air flow is sized for the sensible peak on a traditional air system, and ventilation for a dedicated outdoor air system (DOAS) only.

Property	Value	Notes
Cooling supply air temperature	N/A	Determined by the air system (typically 12.7778°C).
Heating supply air temperature	40°C

Reheat Coil

The reheat coil has the following assumptions.

• The electric resistence coil is 100% efficient.
• The furnace reheat coil is 80% efficient.
• The hot water reheat coil has the following properties.

Property	Value	Notes
Coil entering air temperature	Varied	Determined by the air system (typically between 12.7778°C and 18.3333°C by default).
Coil leaving air temperature	40°C
Hot water design inlet temperature	N/A	Set by the hot water loop if hot water coil is used in the system.
Hot water design outlet temperature	N/A	Set by the hot water loop if hot water coil is used in the system.

Supply Fan

The supply fan has the following properties.

Property	Value	Notes
Pressure Rise	250 Pa
Total Efficiency	70%
Motor Efficiency	94%
Flow Mode	Constant