3.4.5 Receptacle and Process Loads

Applicability

All building projects

Definition

Receptacle power is power for typical general service loads in the building. Receptacle power includes equipment loads normally served through electrical receptacles, such as office equipment and printers, but does not include either task lighting or equipment used for HVAC purposes. Receptacle power values are generally higher than the largest hourly receptacle load that is actually modeled because the receptacle power values are modified by the receptacle schedule, which approaches but does not exceed 1.0.

The equipment plugged into receptacles are considered unregulated loads, hence no credit is given for improvements to the efficiency of that equipment, when the PRM is used for compliance with the standard. However, when quantifying performance that exceeds the requirements of Standard 90.1, credit for reductions in receptacle power may be granted as described below under Baseline Building. 

Control of those receptacles is regulated by Standard 90.1 and that is discussed in descriptor Automatic  Receptacle Control.

Units

Total power (W) for the space or power density (W/ft²)

Software shall also use the prescribed values below to specify the latent heat gain fraction and the radiative/convective heat gain split.

For software that specifies the fraction of the heat gain that is lost from the space, this fraction shall be prescribed at 0 unless the equipment is located under an exhaust hood.

Input Restrictions

Receptacle and process loads, such as those for office and other equipment, shall be estimated based on the building type or space type category. These loads shall be included in simulations of the building and shall be included when calculating the baseline building performance and proposed building performance.

For Standard 90.1-2019, receptacle loads in the proposed design may be calculated in one of two ways:

• As designed or assumed by the design team for loads calculation. Great care must be used in the application of space design receptacle loads from HVAC or electrical designers as these may not include appropriate diversity to represent annual operation.
• Standard 90.1-2019 recommended defaults may be used, in which case the same values must be used for the baseline building and there is no credit for reductions.

Baseline Building

The receptacle power and process loads in the baseline building shall be the same as the proposed design.

However, when quantifying performance that exceeds the requirements of Standard 90.1 (but not when using the Performance Rating as an alternative path for minimum standard compliance ), with approval of the rating authority, variations of the power requirements, schedules, or control sequences of the equipment modeled in the baseline building from those in the proposed design shall be allowed by the rating authority based upon documentation that the equipment installed in the proposed design represents a significant verifiable departure from documented conventional practice. In such bases, the baseline shall be determined based on prescriptive requirements in Standard 90.1-2019. When no such prescriptive requirements exisit, it shall be equal to requirements of other efficiency or equipment codes or standards applicable to the design of the building systems and equipment.

The burden of this documentation is to demonstrate that accepted conventional practice would result in baseline building equipment different from that installed in the proposed design. If baseline building plug loads differ from the proposed building, this input must be flagged and instructions given to provide the proper documentation.

Applicability

All projects

Definition

The electrical input to the equipment ultimately appears as heat that contributes to zone loads. This heat can be divided into four different fractions. These are given by the input fields:

• Fraction Latent: This field is a decimal number between 0.0 and 1.0 and is used to characterize the amount of latent heat given off by electric equipment in a zone. The number specified in this field will be multiplied by the total energy consumed by electric equipment to give the amount of latent energy produced by the electric equipment. This energy affects the moisture balance within the zone.
• Fraction Radiant: This field is a decimal number between 0.0 and 1.0 and is used to characterize the amount of long-wave radiant heat being given off by electric equipment in a zone. The number specified in this field will be multiplied by the total energy consumed by electric equipment to give the amount of long wavelength radiation gain from electric equipment in a zone.
• Fraction Lost: This field is a decimal number between 0.0 and 1.0 and is used to characterize the amount of “lost” heat being given off by electric equipment in a zone. The number specified in this field will be multiplied by the total energy consumed by electric equipment to give the amount of heat that is “lost” and does not impact the zone energy balances. This might correspond to electrical energy converted to mechanical work or heat that is vented to the atmosphere.
• Fraction Convected: This field is a decimal number between 0.0 and 1.0 and is used to characterize the fraction of the heat from electric equipment convected to the zone air.

The sum of all 4 of these fractions should be 1.

Units

Data structure: fraction

Input Restrictions

As designed. If not specified by the user, default values for receptacle power heat gain fractions will be used.

Radiative = 0.20, Latent = 0.00, Convective = 0.80, Lost =0.00

Baseline Building

Same as proposed

Applicability

All projects

Definition

Schedule for receptacle power loads used to adjust the intensity hourly to reflect time-dependent patterns of usage. These schedules are assumed to reflect the mandatory automatic receptacle control requirements.

Units

Data structure: schedule, fraction

Input Restrictions

Actual schedules shall be used when known. Default schedules documented in COMNET Appendix C (COMNET 2017) can be used when design schedules are not available.

Baseline Building

Schedules for the baseline building shall be identical to those for the proposed design except when-

• Receptacle controls are installed in spaces not required by Standard 90.1-2019 Section 8.4.2. In this case the schedule can differ between baseline and proposed and the receptacle schedule for the proposed building can be modified as explained in the descriptor ‘Automatic Receptacle Control’.Or, when quantifying performance that exceeds the requirements of Standard 90.1 (but not when using the Performance Rating as an alternative path for minimum standard compliance ),with approval of the rating authority, variations of the power requirements, schedules, or control sequences of the equipment modeled in the baseline building from those in the proposed design shall be allowed based upon documentation that the equipment installed in the proposed design represents a significant verifiable departure from documented conventional practice. The burden of this documentation is to demonstrate that accepted conventional practice would result in baseline building equipment different from that installed in the proposed design. If baseline building plug loads differ from the proposed building, this input must be flagged and instructions given to provide the proper documentation.

Applicability

All projects with computer rooms

Definition

Schedule for computer room equipment loads used to adjust the intensity hourly to reflect time-dependent patterns of usage. Standard 90.1-2019 requires the use of a randomized schedule for computer rooms. The randomized computer room equipment schedule is intended to capture part load system performance in the proposed and base case models. While it is not realistic to have computer room loads vary drastically month to month, it is common for loads to vary gradually over months or years. The schedule shown here captures this effect in a single annual simulation. It also allows the various load conditions to be simulated under the various weather conditions.

Units

Data structure: schedule, fraction

Input Restrictions

Computer room equipment schedules shall be modeled as a constant fraction of the peak design load per the following monthly schedule:

Month 1, 5, 9—25%

Month 2, 6, 10—50%

Month 3, 7, 11—75%

Month 4, 8, 12—100%

Baseline Building

Same as proposed

Applicability

All projects

Definition

Automatic receptacle controls include devices that control receptacles based on time of day, occupancy sensors or a central control signal based on occupancy as required by Standard 90.1-2019, Section 8.4.2 requires that 50% of all applicable receptacle and 25% of applicable branch circuit feeders to be controlled using automatic receptacle controls which function on either:

a. A scheduled basis using a time-of-day operated control device that turns receptacles off at specific programmed times. This shall be provided for controlled areas of no more than 5000 ft2 and not more than one floor (the occupant shall be able to manually override the control device for up to two hours);

b. An occupant sensor that shall turn receptacles off within 20 minutes of all occupants leaving a space; or

c. An automated signal from another control or alarm system that shall turn receptacles off within 20 minutes after determining that the area is unoccupied.

All controlled receptacles should be uniformly distributed throughout the space.

Plug-in controls devices cannot be used to comply with these requirements

Exceptions to this requirement include:

a. Receptacles specifically designated for equipment requiring continuous operation (24/day, 365 days/year).

b. Spaces where an automatic control would endanger the safety or security of the room or building occupants.

Units

No units

Input Restrictions

As designed. For each space in the proposed building indicate which receptacle control strategies from the list above are included and the percentage of receptacles that are controlled. .

When receptacle controls are installed in spaces not required by Standard 90.1-2019 Section 8.4.2, credit for receptacle controls in the proposed design can be taken by decreasing the receptacle schedule in the proposed building design according to the following.

RPC = RC x 10%

Hence, the receptacle schedule for each hour for the proposed building =

              EPS_pro = EPS_bas x (1- RPC)

Where:

RPC     = Receptacle power credit

RC       = Percentage of receptacles controlled according to one of the methods described above.

EPS_bas  = Baseline equipment power hourly schedule (fraction)

EPS_pro  = Proposed equipment power hourly schedule (fraction)

Baseline Building

Same as proposed before the automatic receptacle control credit is applied

(4)

Applicability

All buildings that have commercial refrigeration for cold storage or display

Definition

The method used to estimate refrigeration energy and to model the thermal interaction with the space where casework is located. Three methods are included in this manual:

• Modeling Defaults

COMNET defaults. With this method, the methodology described above can be used for modeling walk-in refrigerators and freezers. Schedules are assumed to be continuous operation.

• Performance rating method. With this method, the energy modeler takes inventory of the refrigerated casework in the rated building and sums the rated energy use (typically in kWh/day). All refrigeration equipment is then assumed to operate continuously.
• Explicit refrigeration model. With this method, all components of the refrigeration system are explicitly modeled in DOE-2.2R or another hourly simulation program with this capability. This method is not covered by this manual.
• AHRI Rated Energy. Rated energy use in accordance with AHRI 1200.
• 10 CFR 431 Rated Energy. Rated energy use in accordance with 10 CFR 431.

Units

List (see above)

Input Restrictions

When refrigeration equipment in the proposed design is rated in accordance with AHRI 1200 or 10 CFR 431, the rated energy use shall be modeled.

For all other refrigeration equipment shall be modeled using actual equipment capacities and efficiencies using the performance rating method. If actual equipment capacities and efficiencies are not known, COMNET defaults can be used.

Baseline Building

G3.2 New Construction/Major Alterations

If refrigeration equipment is listed in Table 15 and Table 16 of this manual, then the baseline building design shall be modeled according to Table 15 and Table 16. For refrigeration equipment not listed in either of these two tables, the baseline building shall be modeled to be the same as the proposed design.

G3.3 Minor Alterations

If refrigeration equipment is listed in Standard 90.1 2022 Tables 6.8.1-11, 18, 19, or 20, then the baseline building design shall be modeled according to these tables.

For refrigeration equipment not listed in these tables and where projects are modeling credit for exceeding the minimum requirements in 90.1-2022 Sections 6.4.5 and/or 6.5.11 projects must demonstrate savings by explicitly modeling refrigeration systems or by providing exceptional calculations that meet the requirements of 90.1-2022 Section G2.5 subject to AHJ approval.

Exception: refrigeration equipment 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 Sections 6.4.1, 6.4.5, and 6.5.11 requirements are inapplicable.

Applicability

All buildings or spaces that have commercial refrigeration for cold storage or display and do not use the explicit refrigeration model

Definition

Commercial refrigeration power is the average power for all commercial refrigeration equipment, assuming constant year-round operation. Equipment includes walk-in refrigerators and freezers, open refrigerated casework, and closed refrigerated casework. It does not include residential type refrigerators used in kitchenettes or refrigerated vending machines. These are covered under receptacle power.

Units

Kilowatts (kW) or W/ft²

Input Restrictions

With the performance rating method, refrigeration power is estimated by summing the kWh/day for all the refrigeration equipment in the space and dividing by 24 hours. The refrigeration power for walk-in refrigerators and freezers is added to this value.

Baseline Building

G3.2 New Construction/Major Alterations

When the performance rating method is used, refrigeration power for casework shall be determined from Table 15 and Table 16; the power for walk-in refrigerators and freezers shall be the same as the proposed design.

G3.3 Minor Alterations

If refrigeration equipment is listed in Standard 90.1 2022 Tables 6.8.1-11, 18, or 19, then refrigeration power for casework shall be determined from Standard 90.1 2022 Tables 6.8.1-11, 18, or 19; the power for walk-in refrigerators and freezers shall be the same as the proposed design except when adjusting for an efficiency improvement over the minimum required efficiency from Standard 90.1 2022 Table 6.8.1-20 and/or when claiming credit for exceeding the minimum requirements associated with 90.1-2022 Sections 6.4.5 and/or 6.5.11.

For refrigeration equipment not listed in Tables 6.8.1-11, 18, or 19 and where projects are modeling credit for exceeding the minimum requirements in 90.1-2022 Sections 6.4.5 and/or 6.5.11 projects must demonstrate savings by explicitly modeling refrigeration systems or by providing exceptional calculations that meet the requirements of 90.1-2022 Section G2.5 subject to AHJ approval.

Exception: refrigeration equipment 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 Sections 6.4.1, 6.4.5, and 6.5.11 requirements are inapplicable.

G3.2 New Construction/Major Alterations and G3.3 Minor Alterations

Variations of the power requirements, schedules, or control sequences of the refrigeration equipment modeled in the baseline building from those in the proposed design shall be allowed by the rating authority based upon documentation that the refrigeration equipment installed in the proposed design represents a significant verifiable departure from documented conventional practice.

The burden of this documentation is to demonstrate that accepted conventional practice would result in Baseline Building refrigeration equipment different from that installed in the proposed design. Occupancy and occupancy schedules shall not be changed.

NOTE: Any variation between proposed and baseline refrigeration power should be reported for rating authority approval and inspection.

Applicability

All buildings that have commercial refrigeration for cold storage or display and use the DOE performance ratings methods

Definition

The fraction of condenser heat that is rejected to the outdoors. For self-contained refrigeration casework, this value will be zero. For remote condenser systems, this value is 1.0 and the heat gain fraction to the space through the condenser is zero. For combination systems, the value should be weighted according to refrigeration capacity.

For refrigeration with self-contained condensers and compressors, the heat that is removed from the space is equal to the heat that is rejected to the space, since the evaporator and condenser are both located in the same space. There may be some latent cooling associated with operation of the equipment, but this may be ignored with the DOE performance ratings methods. The operation of self-contained refrigeration units may be approximated by adding a continuously operating electric load to the space that is equal to the energy consumption of the refrigeration units. Self-contained refrigeration units add heat to the space that must be removed by the HVAC system. Hence, in the scenario where the compressor or compressor rack for the case is separate from the case itself but still within the conditioned zone of the display cases, the remote condenser fraction is zero and all the heat ends up in the zone.  For self contained cases, the heat added to the zone is calculated as shown below,

Where

kW    =   The power of the refrigeration system determined by using the DOE performance rating method (kW)

Q_{sensible-credit} = The rate of heat removal from the space due to the continuous operation of the refrigeration system (Btu/h). A positive number means that heat is being removed from the space.  A negative number means heat is being added to the space.

When the condenser is remotely located, heat is removed from the space but rejected outdoors. In this case, the refrigeration equipment functions in a manner similar to a continuously running split system air conditioner. Some heat is added to the space for the evaporator fan, the anti-fog heaters, and other auxiliary energy uses, but refrigeration systems with remote condensers remove more heat from the space where they are located than they add. The HVAC system must compensate for this imbalance.

For remotely located condensers using the DOE performance rating method, the heat that is removed from the space, i.e. the Q_{sensible credit}, is determined as follows:

Q_{sensible-credit} = [Q_rated * (1-LHR_ratio) * RTF – (Q_rated * Elec_ratio)] * L_case

Where

Q_{sensible-credit} = The rate of heat removal from the space due to the continuous operation of the refrigeration system (Btu/h). A positive number means that heat is being removed from the space. 

Q_rated = case gross rated total refrigeration cooling capacity per unit length (Btu/h)

LHR_ratio = latent heat ratio of the refrigerated case at rated conditions

RTF = runtime fraction of the refrigerated case

Elec_ratio = Ratio of cooling capacity required due to cooling load associated with use of lights, fans, anti-sweat heaters divided by Qrated. Depending on case design, not all electric power per unit length may contribute to cooling load.

L_case = length of the case, ft

Use manufacturer data where available. If unavailable, use the defaults below. Note: these defaults are based on data from a single manuafcturer.

Units

Fraction

Input Restrictions

None

Baseline Building

Same as the proposed design

Applicability

All buildings that have commercial refrigeration for cold storage or display and use the DOE performance ratings methods

Definition

The coefficient of performance (COP) of the refrigeration system. This is used only to determine the heat removed or added to the space, not to determine the refrigeration power or energy.

Units

Fraction

Input Restrictions

This value is prescribed to be 3.6 for refrigerators and 1.8 for freezers3F[1]

Baseline Building

Same as the proposed design

Applicability

All buildings that have commercial refrigeration for cold storage or display

Definition

The schedule of operation for commercial refrigeration equipment. This is used to convert refrigeration power to energy use.

Units

Data structure: schedule, fractional

Input Restrictions

Continuous operation is prescribed

Baseline Building

Same as the proposed design