Preventive Maintenance Strategies and Technologies Can Pave the Path for Next Generation Rooftop HVAC systems

Transcription

1 Preventive Maintenance Strategies and Technologies Can Pave the Path for Next Generation Rooftop HVAC systems Ramin Faramarzi, P.E. Technology Test Centers October 14, 2014

2 Overview 1. Why is HVAC maintenance important? a. Policy Drivers b. CA HVAC Facts c. FAQs Related to HVAC Maintenance 2. What are the Common Faults? 3. What are the Impacts of Common Faults? a. SCE Fault Impact Test Results 4. Solutions for Implementing Enhanced Preventive Maintenance a. FDD Technologies i. SCE FDD Test Results b. Effective Utility Programs: SCE s HVAC Commercial Quality Maintenance Program 5. The Next Generation of RTUs 1

3 1. Why is HVAC Maintenance Important? 2

4 Policy Drivers AB32: GHG Goals By GHG Emissions Reduced 25% Below 1990 Level CLTEESP, Big Bold Energy Efficiency Strategies Commercial New Construction ZNE by 2030 HVAC Market Transformation Goal 4: New HVAC Technologies & System Diagnostics 3

5 California HVAC Facts CA commercial peak demand 15 GW, annual energy use 67 billion kwh 1,2 Cooling = peak demand 4GW, 10 billion kwh (15%) 1,2 At least 10% of commercial HVAC energy due to excessive run time, poorly maintained equipment, and controls problems 3 Single zone packaged and split systems comprise 70% of CA commercial HVAC 4 81% of single zone packaged and split > 65,000 Btu/h California Commercial End-Use Survey Peak demand values are not coincident across multiple end uses and do not sum up to commercial segment total 3. Advanced Automated HVAC Fault Detection and Diagnostics Commercialization Program California Commercial Saturation Survey (CSS) Report FINAL. 4

6 FAQs Related to HVAC Maintenance What are the common faults experienced by HVAC in the field? What are the impacts of faults on comfort, HVAC performance, energy and demand consumption? How can current maintenance practices be enhanced? 5

7 2. What are the Common Faults? 6

8 Lots to choose from, actually 7

9 Choosing Important Common Faults Selected with Industry Experts Guidance 1. Low Refrigerant Charge 2. High Refrigerant Charge 3. Liquid Line Restrictions 4. Non-Condensables 5. Evaporator Airflow Reduction 6. Condenser Airflow Reduction 7. Economizer Communication/Mechanical Faults 8

10 3. What are the Impacts of Common Faults? An overview of SCE Lab Research Findings 9

11 The RTU Test Unit Type Nameplate Charge Refrigerant Expansion Device Nominal Cooling AHRI-Rated Cooling Efficiency Nominal Evaporator Airflow Measured Nominal Condenser Airflow RTU, Fixed Capacity 20 lbs R-410a TXV 5 ton 57,500 Btu/h EER, 15.2 SEER 1750 SCFM 3243 SCFM 10

12 Lab Testing: Strategy & Monitoring Plan Steady state cooling performance AHRI 210/ Measurement points recorded every 20 seconds Performance Metrics: Gross Cooling, Total Power, & Efficiency Faults were tested under various severity levels Economizer fault scenarios were tested outside of AHRI Supply Air Evaporator Fan Condenser Re-heat coil Evaporator Filter R1 R2 TXV R6 Return Air Outside Air Inlet Compressor R3 Condenser Condenser *Blocked off* R5 11 R4 Mass Flow Meter Liquid Line Restriction Valve

13 Tests Tracked Performance based on Fault Severity and Fault Impact Ratio Fault Impact Ratio (FIR) the ratio of impact to efficiency or cooling capacity under faulted vs un-faulted conditions Examples: -10% EER, -10% Cooling Capacity Fault Severity (FS) the level of a fault expressed with reference to actual/normalized measurements Examples: % reduction in indoor airflow, ounces of noncondensables, % reduction in nominal charge 12

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18 What About Multiple Faults? 17

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20 4. Solutions for Implementing Enhanced Preventive Maintenance 19

21 FDD Technologies FDD technologies can bring consistent/reliable understanding of the HVAC system Mitigate existing faults Early prevention Sustain optimal HVAC performance Improved human comfort & equipment life Improved efficiency & reduced impacts to GHG emissions Reduced impacts to economic resources of homeowners 20

22 FDD Barriers and Challenges Need for Understanding FDD Technologies Performance Little/no consistency across technologies, no classifications of FDD technology types with respect to: In-Field vs. Onboard No industry accepted methods to define functions, capabilities, accuracy, reliability High Technology Cost & Unknown End-User Interaction How does it enhance maintenance? What faults exist / likely to occur? Correctly diagnosed? What actions taken, if any? 21

23 SCE FDD Test Results 22

24 FDD Test Units Three FDD test units: two in-field, one onboard Wide variety of alarms/diagnoses types encountered across the three FDD, not all applicable to fault test scope FDD Test Unit A = 6 pertinent alarms/46 total alarm capability FDD Test Unit B = 12 pertinent alarms/49 total alarms capability FDD Test Unit C = 16 pertinent alarms/36 total alarms capability FDD Test FDD Test FDD Test Fault Unit A Unit B Unit C Low Charge High Charge Liquid Line Restrictions Non-Condensables X X Evaporator Airflow Reduction Condenser Airflow Reduction Economizer Mechanical/Communications Faults X X 23

25 Generalizing FDD Output Types 1. No Response the FDD protocol cannot be applied for a given input scenario, or does not give an output because of excessive uncertainty. 2. Correct the operating condition, whether faulted or unfaulted, is correctly identified 3. False Alarm no significant fault is present, but the protocol indicates the presence of a fault. 4. Misdiagnosis a significant fault is present, but the protocol misdiagnoses what type of fault it is. 5. Missed Detection a significant fault is present, but the protocol indicates that no fault is present. 1. A Method For Evaluating Diagnostic Protocols For Packaged Air Conditioning Equipment. 24

26 Diagnostics Analysis is based on a minimum Fault Threshold Air-side efficiency degradation fault recognized if Fault Impact Ratio >10% Refrigerant overcharge fault recognized if overcharge > 5% Overcharge impact on steady-state performance not significant, but reliability concerns due to low superheat and slugging of the compressor 25

27 Diagnostics Analysis Summary No clear top-performer Methodology for making FDD performance transparent needs industry acceptance Acceptable FIR thresholds will vary across different customers 26

28 A Sample of Diagnostic Messages Some technologies indicate multiple different potential causes, others narrow down the root cause further Some technologies are able to illustrate multiple simultaneous faults FDD technologies bring different kinds of value to enhancing HVAC maintenance 30% Low Charge, AHRI ID/OD Circuit A Low Refrigerant Pressure - Low refrigerant charge - Dirty filters - Evaporator fan turning backwards - Loose or broken fan belt FDD Test Unit A - Plugged filter drier - Faulty transducer - Excessively cold return air - Stuck open economizer when the ambient temperature is low Alert: Add Charge / Leak check and repair: Add FDD Test Unit B charge because this is a TXV unit with low subcooling Low capacity or possible high airflow, measure airflow directly. Undercharged, add refrigerant until actual subcooling reaches target subcooling. FDD Test Unit C Actual subcooling is 4.9 F and target subcooling is 16.0 F. Condenser airflow OK. Outdoor amp draw OK. 27

29 Effective Utility Programs Strategies First, Quality Renovation (QR) Optimize system performance (unit and ductwork) Second, (If needed) Early Retirement (ER) Replace aging units with high-efficiency Third (With step Two) Quality Installation (QI) Install high-efficiency units and optimize unit and ductwork performance Fourth, Quality Maintenance (QM) Maintain high performance with multi-year contract An Effective Utility Program should leverage appropriate FDD solutions for each of above strategies, and promote specialized training to enhance skill sets of the workforce 28

30 The Mechanisms for Realizing Enhanced System EER Minimum Fed Rated EER,

31 5. The Next Generation of RTUs High efficiency / low peak demand Natural refrigerants Onboard FDD 2-way communication DR-capable Integration with renewables 30

32 Questions? Ramin Faramarzi, P.E. Technology Test Centers 31