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 Presenter: Ramin Faramarzi, P.E., Principal Engineer, National Renewable Energy Lab

2 Acknowledgement The content of this presentation was developed based on a multi-phase project conducted by Southern California Edison s Technology Labs. This project was mostly funded by the Emerging Technologies program.

3 Agenda 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: c. The Next Generation of RTUs

4 1. Why is HVAC Maintenance Important?

5 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

6 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.

7 Component Power Draw in a RTU Compressor 83.7% Misc. 0.4% Evaporator Fan 11.5% Condenser Fan 4.4% 115F ambient test average of six units Cooling accounts for 8% of all energy consumed in commercial buildings In warmer climates this can be as high as 33%

8 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?

9 2. What are the Common Faults?

10 Lots to choose from, actually Air Conditioner / Heat Pump - Cooling Mode Air Conditioner / Heat Pump - Cooling Mode Air-side Circuit Air-side Circuit Indoor Section Outdoor Section Economizer Faults Return/Supply openings Filter UV Lamp Evaporator Indoor Section Fan Combustion chamber Burner Flue Faults Inlet/Outlet Condenser Condenser Fan Outdoor sensor Return air sensor Mixed air/discharge sensor Economizer controller Outside air damper Outside air damper motor Actuator / Linkage Symptoms Low Airflow Reduced heat transfer effectiveness (nonairflow) Variable Speed Drive Motor contactor Bearing Fan blades Fan Housing Deterioration Leaks Moisture problems Condensation Combustion products Deterioration Leaks Moisture problems Condensation Combustion products Deterioration Leaks Moisture problems Condensation Combustion products Low Airflow Sheave Fan blades Fan Housing Fan drive Obstruction Dirty Obstruction Improper fit Compromised housing seal integrity Belt Sheave Fan drive Belt Dirty/damaged Obstruction Damaged Fouling Obstruction Damaged Surfaces/Fins Fouling Damaged Surfaces/Fins Improper Operation Pitting/other damage Wear Wear Improper Tension Wear Improper Alignment Dirty/damaged Dirty/damaged Wear Poor alignment Poor bearing seating Fouling Obstruction Damaged Surfaces/Fins Fouling Damaged Surfaces/Fins Improper Operation Pitting/other damage Wear Wear Improper Tension Wear Improper Alignment Dirty/damaged Dirty/damaged Wear Poor alignment Poor bearing seating Bad condition/setting/operation Bad condition/setting/operation Bad condition/setting/operation Bad condition / Changeover controller setting / operation High limit setpoint Low limit setpoint Range/action setup incorrect Minimum OA Obstruction / stuck damper Dirty/no lubrication/damaged Damaged components No lubrication Bad setting Broken Wear Mis-aligned Loose No lubricant Not economizing when it should Excess outdoor air Low ventilation Air Conditioner / Heat Pump - Cooling Mode Air Conditioner / Heat Pump - Cooling Mode Air-side Circuit Reduced heat transfer effectiveness (nonairflow) Variable Speed Drive Motor contactor Bearing Refrigerantside Circuit Control system Misc. Cabinet Ducts Refrigerant charge Refrigerant Circuit Lines Compressor Expansion Device Filter/Drier Thermostat Sensors Control Box Low ambient head pressure control Other devices? Symptom Steam system traps, pumps, and controls P-trap Other field-servicable bearings Condensate drain pan Condensate drain line Exposed ductwork External piping Vapor barrier Insulation Other areas Symptoms Faults Panels Fasteners Gaskets Curbs Symptoms High Charge Low Charge Liquid Line Suction Line Discharge Line Evaporator circuit Condenser circuit Valves Bearings Oil Variable Speed Drive Motor contactor Symptoms Capillary Tube Thermostatic Expansion Valve (TXV) Electronic Expansion Valve (EEV) Faults Missing Filter Panel Damaged Missing Fan Access Panel Damaged Missing Compressor Panel Damaged Missing Damaged Damaged Damaged High pressure drop Improper install Obstruction / Restriction Air leaks High Charge High Charge - Compromised Blend Low Charge Low Charge - Compromised Blend Non-Condensables / Contaminants Bend / Obstruction Refrigerant leaks Bend / Obstruction Refrigerant leaks Bend / Obstruction Refrigerant leaks Refrigerant leaks Refrigerant leaks Valve Leakage Seized Bearing Low Oil level/pressure Improper Operation Pitting/other damage Short cycling Obstruction Obstruction Sensing Bulb Fault Improper Adjustment Obstruction Sensor Fault Improper Adjustment Obstruction Incorrect scheduling Improper Programming/Adjustment Improper Location Communication Failure Failure/fault Drift Dirt/debris Loose terminations Damaged components Software/algorithm modifications needed Improper operation Improper operation Dirty/broken Not primed Wear Biological growth Biological growth Obstruction Missing insulation Missing insulation compromised integrity Biological growth Moisture carryover beyond drain pan from evaporator condensate Biological growth Efficiency does not meet unit rating Capacity does not meet unit rating

11 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

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

13 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

14 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

15 R4 Condenser Refrigerant-side State Points Mass Flow Meter R5 R6 TXV Liquid Line Restriction Valve Compressor R3 R2 R7 Evaporator R1

16 Air-side State Points A9 Test Chamber - Indoor Section Airflow Measurement Apparatus Supply Air Duct A6 Supply Air Return Air A1 Evaporator Filter Outside Air Inlet Partition A5 A4 A3 Evaporator Fan Mixed Air A2 *Blocked off* Compressor Top View Condenser Condenser Fan Condenser A7 Condenser A8 Duct Airflow Measurement Apparatus Test Chamber - Outdoor Section Duct Airflow Measurement Apparatus A11 Airflow Measurement Apparatus Supply Duct Access Panel Compressor Condenser A10 C o n d e n s e r A8 Test Chamber - Indoor Section Partition Outside Air Inlet *Blocked off* Side View Test Chamber - Outdoor Section

17 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 Intensity (FI) the level of a fault expressed with reference to actual/normalized measurements Examples: % reduction in indoor airflow, ounces of noncondensables, % reduction in nominal charge

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29 What About Multiple Faults?

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34 4. Solutions for Implementing Enhanced Preventive Maintenance

35 FDD Technologies FDD technologies either on-board or in-field provide a better understanding of HVAC system performance that can help: Lower operational cost Mitigate existing faults Early prevention Sustain optimal performance Improved human comfort & equipment life Improved efficiency & reduced impacts to GHG emissions Reduced impacts to economic resources of building owner

36 FDD Barriers and Challenges Need for Understanding FDD Technologies Performance Little/no consistency across technologies, no classifications of FDD 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?

37 SCE FDD Test Results

38 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

39 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 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.

40 Our 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

41 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 High Severity, -30% Circuit A Low Refrigerant Pressure - Low refrigerant charge - Dirty filters - Evaporator fan turning backwards - Loose or broken fan belt FDD Test Unit _ - Plugged filter drier - Faulty transducer - Excessively cold return air - Stuck open economizer when the ambient temperature is low FDD Test Unit _ FDD Test Unit _ Low Charge, AHRI ID/OD Alert: Add Charge / Leak check and repair: Add 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. Actual subcooling is 4.9 F and target subcooling is 16.0 F. Condenser airflow OK. Outdoor amp draw OK.

42 Effective Utility Programs Strategies (Smaller RTUs) First, Quality Renovation (QR) Optimize duct performance Second, (If needed) Early Retirement (ER) Avoid continued use of aging units (still within their useful life), replace w/ high-efficiency Third (With step Two) Quality Installation (QI) Install/optimize high-efficiency units Fourth, Quality Maintenance (QM) Maintain high system performance with multi-year contract of enhanced maintenance services 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

43 Commercial Retrocommissioning (RCx) Program (Large Built-up Systems) Larger, built-up HVAC RCx is a process for improving the performance of a building s individual systems (lighting, HVAC, controls, etc.). This process first identifies opportunities for increasing energy efficiency and improving the comfort of your building, with a focus on opportunities that are low-cost and have quick financial payback periods.

44 Wrap Up The Next Generation of RTUs High efficiency / low peak demand Low GWP/Natural refrigerants TES Integration Advanced Controls Onboard FDD Connectivity DR-capable Integration with renewables

45 Additional Resources Commercial FDD Reports Development of a Fault Detection and Diagnostics Lab Test Method for a Commercial Packaged Rooftop Unit. Emerging Technologies Coordinating Council. Lab Assessment of FDD Technologies on a Commercial Packaged RTU. Emerging Technologies Coordinating Council. Evaluating the Effects of Common Faults on a Commercial Packaged Rooftop Unit. Emerging Technologies Coordinating Council. Residential FDD Reports Development of a FDD Laboratory Test Method for a Residential Split System. Emerging Technologies Coordinating Council. Assessment of a Retrofit FDD Tool on a Residential Split System. Emerging Technologies Coordinating Council. Evaluating the Effects of Common Faults on a Residential Split System. Emerging Technologies Coordinating Council.

46 Questions? Ramin Faramarzi, P.E. Principal Engineer National Renewable Energy Lab

47 Appendix

48 Analyzing FDD Outputs

49 Analyzing FDD Outputs

50 Analyzing FDD Outputs

51 Analyzing FDD Outputs (No Faults present)

52 Diagnostics Analysis Summary FDD Test Unit A B C (In-Field Sensor Inputs) C (Lab Sensor Inputs) *Applicable Scenarios **Scenarios that Exceed Fault Threshold Sum of Total Outputs Output Category Output Count Output Rate No response? Correct Response? False Alarm? Misdiagnosis? Missed Detection? No response? Correct Response? False Alarm? Misdiagnosis? Missed Detection? No response? Correct Response? False Alarm? Misdiagnosis? Missed Detection? No response? Correct Response? False Alarm? Misdiagnosis? Missed Detection? Total Scenarios = 45 (31 crossed fault threshold) Methodology for making FDD performance transparent needs industry acceptance Setting the right metrics & expectations