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• Obtain measured RMS watt/fixture data for pre-retrofit and post-retrofit fixtures.

• Count the fixtures associated with each functional area in the building (e.g., areas that have different usage profiles).

■ Define the lighting usage profiles for each functional area using the appropriate information that represents lighting usage profiles (e.g., continuously on, on during evening hours, etc.).

• Calculate lighting energy usage characteristics.

Method #2: Before/after measured lighting power levels with sampled before/after diversity profiles.

Description: i) Measure lighting power levels using RM S watt meter for a sample of the pre-retrofit fixtures and the post-retrofit fixtures, ii) measure the lighting usage profiles using light loggers or portable metering attached to the lighting circuits.

Application: Any exterior lighting or interior lighting with predictable usage profiles. Steps:

• Measure watt/fixture using RMS watt meter for pre-retrofit and post-retrofit fixtures.

• Count the fixtures associated with each functional area in the building (i.e., areas that have different usage profiles).

• Sample lighting usage profiles for each functional area using lighting loggers and/or portable submetered RMS watt meters on lighting circuits.

• Calculate lighting energy usage characteristics.

Method #3: Baseline measured lighting power levels with baseline sampled diversity profiles and post-retrofit power levels with continuous diversity profile measurements.

Description: i) Obtain lighting power levels using RMS watt'fixture measurements for the pre-retrofit fixtures and the post-retrofit fixtures, ii) sample the baseline lighting usage profiles using light loggers or RMS watt measurements on submetered lighting circuits, iii) continuously measure the post-retrofit lighting usage profiles using light loggers or RMS watt measurements on submetered lighting circuits.

Application: Any exterior lighting or interior lighting.

Steps:

• Obtain lighting power levels using RMS watt/fixture measurements for the pre-retrofit fixtures and the post-retrofit fixtures.

• Sample the baseline lighting usage profiles using light loggers or RMS watt measurements on submetered lighting circuits.

• Continuously measure the post-retrofit lighting usage profiles using light loggers or RMS watt measurements on submetered lighting circuits.

• Calculate lighting energy usage characteristics.

Method #4: Baseline measured lighting power levels with baseline sampled diversity profiles and post-retrofit continuous sub-metered lighting.

Description: i) Obtain lighting power levels using RMS watt/fixture measurements for the pre-retrofit fixtures, ii) sample the baseline lighting usage profiles using light loggers or RMS watt measurements on submetered lighting circuits, iii) continuously measure the post-retrofit lighting power usage using RMS watt measurements on submetered lighting circuits.

Application: Any exterior lighting or interior lighting.

Steps:

• Obtain lighting power levels using RMS watt/fixture measurements for the pre-retrofit fixtures.

• Sample the baseline lighting usage profiles using light loggers or RMS watt measurements on submetered lighting circuits.

• Continuously measure the post-retrofit lighting usage using RMS watt measurements on submetered lighting circuits.

• Calculate lighting energy usage characteristics.

Method #5: Method #1, #2, or #3 with stipulated thermal effects.

Description: i) Obtain lighting power profiles and usage using Method(s) #1, #2, #3, or #4 ii) Calculate the heating or cooling system efficiency using HVAC component isolation methods described in this document, iii) Calculate decrease in cooling load and increase in heating load.

Application: Any iuterior lighting.

Steps:

• Obtain lighting power profiles and usage using Method(s) #1, #2, or #3,

• Calculate the heating or cooling system efficiency using FiVAC component isolation methods described in this document,

• Calculate lighting energy usage characteristics.

• Calculate decrease in cooling load and increase in heating load.

Method #6: Before/after sub-metered lighting and thermal measurements.

Description: i) Obtain lighting energy usage by measuring RMS lighting use continuously at the sub-metered level for pre-retrofit and post-retrofit conditions, ii) Obtain thermal energy use data by measuring submetered cooling or heating energy use for pre-retrofit and post-retrofit conditions, iii) develop representative lighting usage profiles from the sub-metered lighting data.

Application: Any interior lighting projects.

Any exterior lighting projects (no thermal interaction).

Steps:

• Obtain measured sub-metered lighting data for pre-retrofit and post-retrofit periods.

• Develop representative lighting usage profiles from the sub-metered lighting data.

• Calculate lighting energy usage characteristics.

• Calculate decrease in cooling load and increase in heating load.

27.12. The savings are determined by comparing the annual lighting energy use during the baseline period to the annual lighting energy use during the post-retrofit period. In Methods #5 and #6 the thermal energy effect can either be calculated using the component efficiency methods or it can be measured using whole-building, before-after cooling and heating measurements. Electric demand savings can be calculated using Methods #5 and #6 using diversity factor profiles from the pre-retrofit period and continuous measurement in the post-retrofit period. Peak electric demand reductions attributable to reduced chiller loads can be calculated using the component efficiency tests for the chillers. Savings are then calculated by comparing the annual energy use of the baseline with the annual energy use of the post-retrofit period.

F. HVAC Systems

As mentioned previously, during the 1950s and 1960s most engineering calculations were performed using slide rules, engineering tables and desktop calculators that could only add, subtract, multiply and divide. In the 1960s efforts were initiated to formulate and codify equations that could predict dynamic heating and cooling loads, including efforts to simulate HVAC systems. In 1965 ASHRAE recognized that there was a need to develop public-domain procedures for calculating the energy use of HVAC equipment and formed the Presidential Committee on Energy Consumption, which became the Task Group on Energy Requirements (TGER) for Heating and Cooling in 1969.125 TGER commissioned two reports that detailed the public domain procedures for calculating the dynamic heat transfer through the building envelopes,126 and procedures for simulating the performance and energy use of HVAC systems.127 These procedures became the basis for today's public-domain building energy simulation programs such as BLAST, DOE-2, and EnergyPlus.128-129

In addition, ASHRAE has produced several additional efforts to assist with the analysis of building energy use, including a modified bin method,130 the HVAC-01131 and HVAC-02132 toolkits, and HVAC simulation accuracy tests133 which contain detailed algorithms and computer source code for simulating secondary and primary HVAC equipment. Studies have also demonstrated that properly calibrated simplified HVAC system models can be used for measuring the performance of commercial HVAC systems.134'135'136,137

Table 27.12: Lighting Calculations Methods from ASHRAE Guideline 14-2002.124
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