Unit Ventilator

Unit ventilators provide a controlled means of introducing conditioned outdoor air during the heating season.

Required Objects

The unit ventilator must have the following property.

• It must be attached to a conditioned zone.

Design Assumptions

If the Draw Ventilation property is selected, the following will occur.

• The unit will provide the design outdoor air flow.
• The fan will run constantly during occupied hours.

If the Draw Ventilation property is not selected, the following will occur.

• The unit will not provide any ventilation.
• The fan will cycle on and off to meet conditioning needs.

Property	Value	Notes
System air flow	Constant
Cooling supply air temperature	12.78°C
Heating supply air temperature	40°C

Cooling Coil

The cooling coil has the following assumptions.

• The DX coil is single-speed with aa rated COP of 3.0.
• The sensible-to-latent heat ratio is auto-sized to meet the system needs during sizing.
• The chilled water coil has the following assumptions.

Property	Value	Notes
Coil entering air temperature	N/A	Determined by the design day.
Coil leaving air temperature	~11.11°C	Calculated from the air system supply air temperature minus fan heat generated (typically about 1.5°C - 2°C).
Chilled water design inlet temperature	N/A	Set by the chilled water loop if chilled water coil is used in the system.
Chilled water design outlet temperature	N/A	Set by the chilled water loop if chilled water coil is used in the system.

Heating Coil

The heating coil has the following assumptions.

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

Property	Value	Notes
Coil leaving air temperature	40°C
Hot water design inlet temperature	N/A	Set by the hot water loop.
Hot water design outlet temperature	N/A	Set by the hot water loop.

Supply Fan

The supply fan has the following properties:

Property	Value	Notes
Pressure rise	250 Pa
Total efficiency	70%
Motor efficiency	94%