3.7.6.2 Preheat Coil

The baseline system shall be modeled with a preheat coil controlled to a fixed setpoint 20°F less than the design room heating temperature setpoint.

Preheat Coil Capacity
Applicability	Systems with a preheat coil located in the outside air stream
Definition	The heating capacity of a preheating coil at design conditions.
Units	Btu/h
Input Restrictions	As designed
Baseline Rules	For baseline systems 5 through 8, the baseline system shall be modeled with a preheat coil controlled to a fixed setpoint of 20 °F less than the design room heating setpoint. See G3.1.3.19.

Preheat Coil Type
Applicability	Systems with a preheat coil located in the outside air stream
Definition	The heating source of a preheating coil. The choices are: electric resistance gas furnace hydronic (supplied by boiler)
Units	List (see above)
Input Restrictions	As designed
Baseline Rules	The heating source for the baseline preheat coil shall be the same as the baseline system. For baseline systems, 5 and 7, the preheat coils will be hydronic. Buildings with baseline system 6 and 8 will be modeled with electric resistance preheat coils.

Preheat Coil Efficiency
Applicability	Systems with a gas preheat coil
Definition	The heating efficiency of a preheating coil at design conditions
Units	Unitless
Input Restrictions	As designed, default is 80%
Baseline Rules	Not applicable. Baseline building would have preheat coils only for systems 5-8 which would either be electric resistance or hydronic.

For systems 5 through 8, the baseline will be modeled with preheat coil in the mixed air stream controlled to a fixed setpoint 20°F less than the design zone heating temperature setpoint

Preheat Coil Capacity
Applicability	Proposed buildings with preheat coils and baseline systems 5 through 8
Definition	The heating capacity of a preheating coil at design conditions
Units	Btu/h
Input Restrictions	As designed
Baseline Building	For baseline systems 5 through 8, the baseline will be modeled with preheat coil controlled to a fixed setpoint 20°F less than the design zone heating temperature setpoint. If there are multiple zone heating setpoints, the preheat setpoint will be determined by the zone with the highest heating temperature setpoint. The preheat coil capacity will be oversized by 25%. Sizing calculations shall be based on the heating design day and cooling design day conditions, as defined in Section 3.2.3 of this document. Oversizing would be carried out at zone level where the sizing parameters would be applied to the zone design’s heating coil loads.

*Preheat Coil Type*
Applicability	Baseline systems 5 through 8
Definition	The heating source of a preheating coil. The preheat coil could be electric resistance, gas fired, or a hydronic heating coil.
Units	List: Electric Resistance, Gas Fired, Hydronic
Input Restrictions	As designed
Baseline Building	The heating source for baseline systems 5 and 7 will be hydronic. Buildings with baseline systems 6 and 8 will be modeled with electric resistance preheat coils.

*Preheat Coil Efficiency*
Applicability	Systems with a preheat coil with gas heating
Definition	The heating efficiency of a preheating coil at design conditions
Units	Percentage
Input Restrictions	As designed
Baseline Building	Not applicable. Baseline building would have preheat coils only for systems 5 through 8 that would either be electric resistance or hydronic.

For Standard 90.1-2022 Section G3.2 systems 5 through 8, the baseline will be modeled with preheat coil in the mixed air stream controlled to a fixed setpoint 20°F less than the design zone heating temperature setpoint.

For Standard 90.1-2022 Section G3.3, a preheat coil is modeled in the baseline if there is a preheat coil in the proposed design.

Preheat Coil Capacity
Applicability	Proposed buildings with preheat coils and baseline systems 5 through 8
Definition	The heating capacity of a preheating coil at design conditions
Units	Btu/h
Input Restrictions	As designed
Baseline Building	G3.2 New Construction/Major Alterations For baseline systems 5 through 8, the baseline will be modeled with preheat coil controlled to a fixed setpoint 20°F less than the design zone heating temperature setpoint. If there are multiple zone heating setpoints, the preheat setpoint will be determined by the zone with the highest heating temperature setpoint. The preheat coil capacity will be oversized by 25%. Sizing calculations shall be based on the heating design day and cooling design day conditions, as defined in Section 3.2.3 of this document. Oversizing would be carried out at zone level where the sizing parameters would be applied to the zone design’s heating coil loads. G3.3 Minor Alterations The baseline shall be modeled with a preheat coil if there is a preheat coil specified in the proposed. Baseline shall be modeled such that the preheat coils have controls that stop their heat output whenever mechanical cooling, including economizer operation, is occurring. Exception: the preheat setpoint should be modeled the same in the baseline and proposed if, based on the requirements of 90.1-2022 Section 6.1.4 and the scope of the alteration, 90.1-2022 Section 6.5.2.5 requirements are inapplicable. Preheat coil capacity for the baseline design shall be sized proportionally to the capacities in the proposed design based on sizing runs—i.e., the ratio between the capacities used in the annual simulations and the capacities determined by the sizing runs shall be the same for both the proposed design and baseline building design.

Preheat Coil Type
Applicability	Baseline systems 5 through 8
Definition	The heating source of a preheating coil. The preheat coil could be electric resistance, gas fired, or a hydronic heating coil.
Units	List: Electric Resistance, Gas Fired, Hydronic
Input Restrictions	As designed
Baseline Building	G3.2 New Construction/Major Alterations The heating source for baseline systems 5 and 7 will be hydronic. Buildings with baseline systems 6 and 8 will be modeled with electric resistance preheat coils. G3.3 Minor Alterations Same as the proposed design.

Preheat Coil Efficiency
Applicability	Systems with a preheat coil with gas heating
Definition	The heating efficiency of a preheating coil at design conditions
Units	Percentage
Input Restrictions	As designed
Baseline Building	G3.2 New Construction/Major Alterations Not applicable. Baseline building would have preheat coils only for systems 5 through 8 that would either be electric resistance or hydronic. G3.3 Minor Alterations All preheat coil equipment in the baseline building design that is included in the scope of the alteration shall be modeled at the minimum efficiency levels, both part load and full load, in accordance with Sections 6.4. Where the efficiency rating includes supply fan energy, calculate the minimum COPnfheating using the equation from Standard 90.1-2022 Section 12.5.2(c) as applicable. Where multiple HVAC zones or residential spaces are combined into a single thermal block, the efficiencies for baseline HVAC systems should be based on the equipment capacity of the thermal block divided by the number of HVAC zones or residential spaces.