3.7 HVAC Secondary Systems

This group of building descriptors relate to the secondary HVAC systems. There is not a one-to-one relationship between secondary HVAC system components in the proposed design and the baseline building since the baseline building system is determined from building type, size and heating source. Appendix A shows the applicability of each building descriptor for the eight baseline building systems. Depending on the nature of the proposed design, any of the building descriptors could apply.

90.1-2016 BM

This group of building descriptors relate to the secondary HVAC systems. There is not a one-to-one relationship between secondary HVAC system components in the proposed design and the baseline building since the baseline building system is determined from building type, size and heating source. See Table 3.1-1, 3.1-2 and 3.1-3. Additional detail on the baseline building systems is provided in the tables below.  Depending on the nature of the proposed design, any of the building descriptors could apply.

Table 3.7-1: Baseline Building System Type

Baseline Building System

System Type

System 1 – PTAC

Single Zone Heating and Cooling

System 2 – PTHP

Single Zone Heating and Cooling

System 3 – PSZ-AC

Single Zone Heating and Cooling

System 4 – PSZ-HP

Single Zone Heating and Cooling

System 5 – Packaged VAV with Reheat

Single Duct VAV

System 6 – Packaged VAV with PFP boxes

Single Duct VAV

System 7 – VAV with Reheat

Single Duct VAV

System 8 – VAV with PFP boxes

Single Duct VAV

System 9 – Heating and Ventilation

Constant Volume Heat/Vent (no cooling)

System 10 – Heating and Ventilation

Constant Volume Heat/Vent (no cooling)

System 11. SZ–VAV

Single-zone VAV

System 12. SZ-CV-HW

Single zone with hot water heat

System 13. SZ-CV-ER

Single zone with electric resistance heat

 

Table 3.7-2: Summary of Baseline Building Secondary HVAC System Properties

System

Fan Control

Economizer

Cooling Type

Cooling Efficiency.

Minimum Supply T.

Heating Type

Heating Efficiency

Maximum Supply T.

1 PTAC

Constant volume

Not required

Direct Expansion

Minimum SEER or EER based on equipment type and output capacity of proposed unit(s).  Adjusted EER is calculated to account for supply fan energy.

20 °F below occupied space cooling setpoint

Hot-water fossil fuel boiler

Minimum AFUE, Thermal Efficiency, COP or HSPF based on equipment type and output capacity of baseline unit(s).

20 °F above occupied space heating setpoint

2 PTHP

Electric heat pump

3 PSZ-AC

Integrated economizer with dry-bulb high limit by climate zone. See 6.7.4 ‘Outside Air Controls and Economizer’ for details and exceptions.

Fossil fuel furnace

4 PSZ-HP

Electric heat pump

5 PVAV

Variable volume

Hot-water fossil fuel boiler

6 PVAV / PFP

Electric resistance

7 VAV

Chilled water

See 6.8 Primary Systems

Hot-water fossil fuel boiler

8 VAV / PFP

Electric resistance

9 HV Furnace

Constant volume

Not required

None

None

Fossil fuel furnace

10 HV Electric

Electric resistance

11 SZ-VAV

Variable volume

Integrated economizer with dry-bulb high limit by climate zone. See 6.7.4 for details.

Chilled water

See 6.8 Primary Systems

See note.

12 SZ-CV-HW

Constant Volume

Hot-water fossil fuel boiler

13 SZ-CV-ER

Electric resistance

Table 3.7-3: Summary of Baseline Building Variable Volume Fan Control and Reheat

Code

Supply Fan Control

PFP Fan

Reheat Terminal Flow

5 PVAV

Variable speed controlled by variable speed drives.

The part load performance of VAV fans is required to be modeled in accordance to section ‘Fan Part Load Curve’ in ‘Fan Systems’.

 

Minimum volume setpoint for reheat is highest of 30% of zone peak flow, minimum outdoor air flow rate or airflow rate required by applicable rating authority. See Section 3.6.5 for details

 

6 PVAV / PFP

PIU fan would be constant volume. AHU fan should cycle on only for cooling. Zone fans should provide unoccupied heating.

Fans for PIU units are sized for 50% of peak design primary air

7 VAV

 

 

8 VAV / PFP

PIU fan would be constant volume. AHU fan should cycle on only for cooling. Zone fans should provide unoccupied heating.

Fans for PIU units are sized for 50% of peak design primary air

 

90.1-2019

This group of building descriptors relate to the secondary HVAC systems. There is not a one-to-one relationship between secondary HVAC system components in the proposed design and the baseline building since the baseline building system is determined from building type, size, and heating source. Depending on the nature of the proposed design, any of the building descriptors could apply. The HVAC baseline systems are described in the summary tables below for reference. The details of individual building descriptor definitions can be found in Sections 3.7 and 3.8.

Table 41. System 1 and System 2 Descriptions 

   
System Description Packaged terminal air conditioner (#1) or packaged terminal heat pump (#2)
Supply Fan Control Constant volume
Min Supply Temp 20°F below occupied space cooling setpoint
Cooling System DX
Cooling Efficiency Minimum seasonal energy efficiency ratio (SEER) or EER based on equipment type and output capacity of proposed unit(s). Adjusted EER is calculated to account for supply fan energy.
Maximum Supply Temp 20°F above occupied space heating setpoint
Heating System Hot water boiler (#1) or heat pump (#2)
Heating Efficiency Minimum annual fuel utilization efficiency (AFUE), thermal efficiency, COP, or heating seasonal performance factor (HSPF) based on equipment type and output capacity of baseline unit(s)
Economizer None
Ducts N/A (not ducted)

 

Building EQ

This group of building descriptors relate to the secondary HVAC systems.

Energy Star

This group of building descriptors relate to the secondary HVAC systems.