UNIT 5: ENERGY AUDIT LAB - ADVANCED PROCEDURES, ANALYSIS & REPORTING
5.0 Unit Overview & Learning Objectives
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Purpose: Integrates theoretical knowledge with practical measurement, diagnostic analysis, and professional reporting to complete a full audit cycle.
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Transition: Moves from basic data collection to root-cause diagnosis and actionable, financially-justified recommendations.
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Core Competency: Conduct a standards-compliant (ASHRAE 14, ISO 50002) audit from scoping to final presentation.
5.1 Pre-Audit Planning & Scoping (Advanced)
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Audit Depth Definition:
| Audit Level | Data Detail | Typical Use | | :--- | :--- | :--- | | Preliminary | Walk-through, utility bills | Identify major opportunities | | General | Spot measurements, simple models | List of ECMs with rough estimates | | Detailed | Extensive logging, system-level analysis | Firm savings & costs for investment decisions | | Investment-Grade | High-precision M&V, full simulation | Guaranteed savings for ESCO contracts |
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Stakeholder Engagement: Develop targeted questionnaires for:
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Facility Managers: Operational schedules, maintenance history, capital plans.
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Operators: Control sequences, typical problems, equipment quirks.
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Occupants: Comfort complaints, usage patterns.
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Historical Data Review: Analyze utility bills (12-24 months) for:
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Base load vs. weather-dependent load.
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Seasonal/weekly patterns.
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Anomalies indicating past issues or changes.
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Safety Planning: Mandatory Job Hazard Analysis (JHA) for site-specific risks: Lockout/Tagout (LOTO), confined spaces, electrical arc flash, working at heights.
[!TIP] Exam Focus: Be prepared to differentiate audit levels and list 3-5 key questions for each stakeholder group.
5.2 Advanced Diagnostic Measurements & Data Logging
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Power Quality Analysis:
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Tools: 3-phase power quality analyzer (e.g., Fluke 435).
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Key Metrics: Total Harmonic Distortion (THD) of current/voltage, Voltage Sag/Swell duration/magnitude, Transients, Power Factor (PF).
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Impacts: High THD → motor heating/failure; Low PF → utility penalties; Sags → equipment reset/loss.
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Thermographic Inspection (Advanced):
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Building Envelope: Cold spots = insulation gaps; linear patterns = thermal bridges; moisture = different emissivity/cooling.
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Electrical: Hot connections (>15°C ΔT from phase) indicate loose/failing components.
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Process: Steam leaks (high temp), refractory failure, pump/fan bearing overheating.
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Sub-Metering & Data Logging:
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Strategy: Disaggregate main meter load (e.g., separate HVAC, process, lighting).
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Logger Setup: Sampling interval (1-15 min typical), duration (min 1 full operational cycle), synchronization with utility data.
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Channels: True RMS current clamps, voltage, temperature (RTD/thermocouple), humidity, pressure.
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Airflow & Pressure:
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Anemometer: Hot-wire (low velocity, diffusers); Vane (higher velocity, ducts). Measure velocity (ft/min) → calculate CFM.
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Manometer: Measure pressure differentials (Pa or in. H₂O). Critical for:
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Filter loading (ΔP across filter).
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Duct leakage (pressurize/depressurize zone).
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Building infiltration (blower door test).
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[!TIP] Common Pitfall: Not accounting for emissivity settings in thermography; incorrect anemometer placement (not at duct centerline in traverse).
5.3 Systems-Level Analysis & Interactive Effects
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HVAC Deep Dive:
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Chiller/Boiler Curves: Plot kW/ton or lb/steam vs. % load to find optimal part-load efficiency.
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Economizer: Verify dry-bulb vs. enthalpy control, minimum outdoor air damper position, and integrated with mechanical cooling.
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Duct Leakage: Q = C * (ΔP)^n (Leakage area constant * pressure exponent). Significant loss if >10% of supply CFM.
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Lighting Beyond Retrofit:
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Foot-Candle (fc) Survey: Use light meter to measure maintained vs. initial fc. Compare to IESNA task recommendations.
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Controls Effectiveness: Verify daylight harvesting calibration and occupancy sensor timeout/delay settings.
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Code Compliance: Calculate Lighting Power Density (LPD) = Total Watts / Area (sq.ft). Must meet ASHRAE 90.1 / IECC.
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Process & Motor Systems:
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Motor Efficiency: Slip Method: %Slip = (Ns - Nr)/Ns * 100. Use slip & nameplate data to estimate loaded efficiency.
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VFD Savings: ΔkW ≈ (1 - (Speed Ratio)^3) * Full-load kW. Not linear!
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Compressed Air: Leakage Rate (cfm) = (System pressure - Atmospheric) * Leakage area constant. Costly (1/4" leak ≈ 1 hp @ 8 hrs/day).
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Steam Traps: Ultrasonic or temperature (inlet > outlet for thermostatic traps). Failed open = steam loss; failed closed = water hammer.
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Interactive Effects (CRITICAL):
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Example: LED lighting retrofit reduces internal heat gain → reduces HVAC cooling load (but may increase heating load).
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Quantification: Must adjust HVAC savings for reduced internal gains using bin method or simulation.
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Whole-Building Approach: Use eQUEST/EnergyPlus to model baseline vs. proposed. Captures complex interactions.
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[!TIP] Exam Formula: VFD Energy Savings ≈ $$\displaystyle P_{new} = P_{full} \times (Ratio)^3 $$. Interactive Savings must be subtracted from standalone ECM savings to avoid double-counting.
5.4 Data Management, Analysis, & Savings Calculations
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Data Validation: Check for logger failures, missing data points, utility bill anomalies. Use 3-sigma rule or visual inspection.
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Baseline Energy Modeling:
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Simple Regression: $$\displaystyle E = a + b \cdot DD $$ (Cooling/Heating Degree Days).
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Multiple Regression: $$\displaystyle E = a + b_1 \cdot DD_{cool} + b_2 \cdot DD_{heat} + b_3 \cdot Occupancy $$.
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ECM Savings Algorithm (General Form):
$$ \text{Annual Energy Savings (kWh)} = \frac{(\text{Baseline kW} - \text{Proposed kW}) \times \text{Hours of Operation}}{1000} \times \text{Interactive Factor} $$
$$ \text{Demand Savings (kW)} = (\text{Baseline kW}_{coincident} - \text{Proposed kW}_{coincident}) \times \text{Coincidence Factor} $$
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Financial Metrics:
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Simple Payback (SPB): $$\displaystyle SPB = \frac{\text{Total Project Cost (\ $$)}}{\text{Annual Savings ($/yr)}}$
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Net Present Value (NPV): $$\displaystyle NPV = \sum_{t=1}^{n} \frac{CF_t}{(1+r)^t} - I_0 $$
- $$\displaystyle CF_t $$ = Net cash flow year t, $r$ = discount rate, $$\displaystyle I_0 $$ = initial investment.
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Internal Rate of Return (IRR): Discount rate $r$ where NPV = 0. > Cost of capital = Accept.
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Non-Energy Benefits (NEBs): Quantify if possible (e.g., reduced maintenance hours, increased production throughput, improved occupant comfort/productivity).
[!TIP] Critical: Coincidence Factor (for demand savings) is rarely 1.0. It's the % of time the ECM load coincides with the utility's peak demand period.
5.5 Audit Reporting & Professional Communication
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Standard Report Structure:
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Executive Summary: Top 3-5 ECMs with savings, cost, payback. For C-suite.
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Facility Description & Audit Scope: What was inspected, depth level, dates.
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Baseline Analysis: System-by-system energy use breakdown (pie chart), utility analysis.
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ECM Descriptions: Technical Specs (e.g., "Replace 400W MH with 150W LED"), Savings Calc (show formula/inputs), Cost Estimate, Implementation Notes (disruption, maintenance).
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Prioritized Implementation Plan: Short-term (<1 yr, low cost), Mid-term (1-3 yrs), Long-term (>3 yrs, major cap-ex).
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Appendices: Raw data, detailed calcs, photos, thermograms, equipment lists.
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Technical Writing: Use active voice, quantitative statements ("saves 50,000 kWh/yr" not "significant savings"), standard units (kWh, therms, kW).
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Visual Communication:
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Tables: For ECM summary (cost, savings, payback).
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Charts: Stacked bar for baseline end-use; line chart for utility trends.
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Thermograms: Include in report with temperature scale, emissivity setting, date/time, interpretation caption.
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[!TIP] Common Error: Writing recommendations as problems ("The HVAC system is inefficient"). Correct: "ECM-1: Replace chilled water pump with VFD-controlled unit. Savings: 85,000 kWh/yr. Cost: $12,000. Payback: 2.8 yrs."
5.6 Standards, Protocols, & Quality Assurance
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Key Standards:
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ASHRAE Guideline 14: Measurement of Energy and Demand Savings. Gold standard for M&V methodology.
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ISO 50002: Energy Audits. Requirements for audit process, competence, reporting.
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IPMVP: International Performance Measurement and Verification Protocol. Defines M&V Options (A, B, C, D) for post-implementation verification.
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M&V Options (IPMVP):
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Option A: Retrofit isolation, key parameter measurement.
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Option B: Retrofit isolation, all parameter measurement.
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Option C: Whole-facility utility meter comparison.
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Option D: Calibrated simulation.
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Quality Assurance:
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Peer Review: Independent check of measurement methods, calculations, assumptions.
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Uncertainty Analysis: Combine measurement uncertainty (instrument accuracy) and sampling uncertainty. Report as ±X% on savings.
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Common Error Sources: Incorrect operating hours, ignored interactive effects, outdated equipment inventory, weather normalization mistakes.
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[!TIP] Exam Key: Know which IPMVP option applies. Option C (whole-building) is common for lighting retrofits; Option A/B for single equipment (VFD on a pump).
5.7 Case Studies & Integrated Lab Project
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Capstone Lab Phases:
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Planning: Select campus building (e.g., library, admin block). Define scope (General/Delailed). Create JHA & interview questionnaire.
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Data Collection: Deploy loggers (power, temp), conduct blower door test, infrared scan, take inventory, interview operators.
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Analysis: Develop baseline model (regression), identify ECMs (lighting, HVAC, envelope), calculate savings with interactive adjustments, run financial analysis (NPV/IRR).
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Reporting & Presentation: Compile formal report per 5.5 structure. Prepare 10-slide deck: Problem → Solution → Financials → Recommendation for different audiences (Director vs. Maintenance Staff).
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Post-Audit: Role in implementation support (spec review, contractor selection) and M&V plan development (selecting IPMVP option).
[!TIP] Project Success Metric: Report is judged on completeness of data, rigor of savings calcs (especially interactions), clarity of recommendations, and professional presentation.
\boxed{\text{Core Exam Themes: Measurement Tools (PQ Analyzer, IR, Anemometer), Savings Formulas (kWh, Payback, NPV), Interactive Effects, Report Structure, M&V Standards (ASHRAE 14, IPMVP)}}