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Furnace Capacity |
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|---|---|
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Applicability |
Systems with a furnace |
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Definition |
The full load heating capacity of the unit |
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Units |
Btu/h |
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Input Restrictions |
As designed. Adjust the capacity if the number of unmet load hours exceeds 300. |
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Baseline Rules |
Autosize with an oversizing factor of 25% (let the software determine heating capacity based on the building loads). If the number of unmet load hours for the baseline exceeds 300, increase the furnace capacity as described in Chapter 2. |
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Furnace Fuel Heating Efficiency |
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Applicability |
Systems with a furnace |
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Definition |
The full load thermal efficiency of either a gas or oil furnace at design conditions. The software must accommodate input in either Thermal Efficiency (Et) or Annual Fuel Utilization Efficiency (AFUE). Where AFUE is provided, Et shall be calculated as follows: (Equation 3.7.6-1) $$E_{t}=(0.0051427\cdot AFUE)+0.3989$$ where
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Units |
Fraction |
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Input Restrictions |
As designed |
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Baseline Rules |
See the values below:
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Furnace Fuel Heating Part Load Efficiency Curve |
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Applicability |
Systems with furnaces |
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Definition |
An adjustment factor that represents the percentage of full load fuel consumption as a function of the percentage full load capacity. This curve shall take the form of a quadratic equation as follows: (Equation 3.7.6-2) $$Fuel_{partload}=Fuel_{rated}\times FHeatPLC$$ (Equation 3.7.6-3) $$FHeatPLC=a+b\cdot\ \frac{Q_{partload}}{Q_{rated}}+c \cdot (\frac{Q_{partload}}{Q_{rated}})^{2}$$ Where
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Units |
Data structure |
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Input Restrictions |
As designed when data is available, otherwise use the default values are provided above. |
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Baseline Rules |
The defaults shall be used. |
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Furnace Fuel Heating Pilot |
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|---|---|
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Applicability |
Systems that use a furnace for heating |
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Definition |
The fuel input for a pilot light on a furnace |
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Units |
Btu/h |
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Input Restrictions |
As designed |
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Baseline Rules |
Zero (pilotless ignition) |
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Furnace Fuel Heating Fan/Auxiliary |
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|---|---|
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Applicability |
Systems that use a furnace for heating and have an auxiliary fan for combustion air. |
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Definition |
The fan energy in forced draft furnaces and the auxiliary (pumps and outdoor fan) energy in fuel-fired heat pumps |
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Units |
Kilowatts (kW) |
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Input Restrictions |
As designed |
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Baseline Rules |
Not applicable |
|
Furnace Capacity |
|
|
Applicability |
Systems with a furnace |
|
Definition |
The full load heating capacity of the unit |
|
Units |
Btu/h |
|
Input Restrictions |
As designed. Adjust the capacity if the number of UMLH exceeds 300. |
|
Baseline Building |
Autosized, with a heating oversizing factor of 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 heating loads, but not the airflow rates. If the number of UMLH for the baseline exceeds 300, heating coil capacity may need to be increased along with system airflow as described in Section 2.7.2 of this document. |
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Furnace Fuel Heating Efficiency |
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Applicability |
Systems with a furnace |
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Definition |
The full load thermal efficiency of either a gas or oil furnace at design conditions. The software must accommodate input in either Thermal Efficiency (Et) or Annual Fuel Utilization Efficiency (AFUE). Where AFUE is provided, Et shall be calculated as follows for both packaged and split systems:
Source: (CEC 2013) For furnaces with efficiency rating prescribed as combustion efficiency, 2% jacket losses will be assumed. Hence: Et = Ec – 2% Where: AFUE = The annual fuel utilization efficiency (%) Et = The thermal efficiency (fraction) Ec = Combustion efficiency |
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Units |
Fraction |
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Input Restrictions |
As designed |
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Baseline Building |
This is applicable to baseline systems 3 and 9. The baseline efficiency requirement is located in Table G3.5.5 of Standard 90.1-2019 and Table 74 of this manual. Where multiple HVAC zones or residential spaces are combined into a single thermal block, the efficiencies for baseline HVAC Systems shall be based on the equipment capacity of the thermal block divided by the number of HVAC zones or residential spaces. Table 74. Efficiency Requirements for Baseline Systems with Fossil Fuel Furnace
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Furnace Fuel Heating Part Load Efficiency Curve |
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Applicability |
Systems with furnaces |
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Definition |
An adjustment factor that represents the percentage of full load fuel consumption as a function of the percentage full load capacity. This curve shall take the form of a quadratic equation as follows:
Where: FHeatPLC = The fuel heating part load efficiency curve Fuelpartload = The fuel consumption at part load conditions (Btu/h) Fuelrated = The fuel consumption at full load (Btu/h) Qpartload = The capacity at part load conditions (Btu/h) Qrated = The capacity at rated conditions (Btu/h) Table 75. Furnace Efficiency Curve Coefficients
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Units |
Data structure |
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Input Restrictions |
As designed when data is available, otherwise defaults curves are required to be used |
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|
Baseline Building |
Default curves are required to be used |
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Furnace Fuel Heating Pilot |
|
|
Applicability |
Systems that use a furnace for heating |
|
Definition |
The fuel input for a pilot light on a furnace |
|
Units |
Btu/h |
|
Input Restrictions |
As designed |
|
Baseline Building |
Zero (pilotless ignition) |
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Furnace Fuel Heating Fan/Auxiliary Power |
|
|
Applicability |
Systems that use a furnace for heating |
|
Definition |
The fan energy in forced draft furnaces and the auxiliary (pumps and outdoor fan) energy in fuel-fired heat pumps |
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Units |
kilowatts (kW) |
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Input Restrictions |
As designed |
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Baseline Building |
Not applicable |