The Revised Method of Test for Residential Water Heating and Its Impact on Incentive Programs Paul Glanville ACEEE Hot Water Forum Tuesday, February 24 th, 2015 Nashville, TN
Overview >How Water Heaters are Rated Today >Changes in the MOT >Test Plan >Test Results >Market Implications 2
How Water Heaters are Rated Today Known Drawbacks of the Current Method of Test/ASHRAE 118.2: Daily hot water draw volumes vary significantly and, on average are lower recent meta-analysis of 10 U.S. studies shows average is 50.6 gal/day. Too few hot water draws favor low storage volumes, same analysis shows median daily draw count is 62 draws/day versus six in the current MOT. Thermostat setting of 135 F is too high, majority of units shipped have out-of-box setting of 125 F. Limited coverage of MOT leaves out many products known to be used in residential applications. 3
Changes in the MOT Legislation puts changes on fast track: The new Federal MOT includes major changes to a procedure largely unchanged for over 25 years: Categorized by output capacity into one of four groups: Very Small, Low, Medium, or High Usage, each with unique draw pattern. The four draw patterns applied are distributed, more realistic, unlike the current MOT. Products are included that were not previously given an Energy Factor (EF), thus were exempt from Energy Star, including hybrid and light commercial products. 4
Impact: Categorization Current MOT rates all products with 64 gal/day draw pattern New MOT (below) has criteria for 4 categories Water Heater Type Draw Pattern Name Daily Hot Water First Hour Draw (Gal.) Rating/Max. GPM Very Small Usage 10 0 FHR < 18 Storage Low Usage 38 18 FHR < 51 Medium Usage 55 51 FHR < 75 High Usage 84 75 FHR Very Small Usage 10 0 GPM < 1.7 Tankless Low Usage 38 1.7 GPM < 2.8 Medium Usage 55 2.8 GPM < 4.0 High Usage 84 4.0 GPM Definition Volume Input 2 < Gal. < 120 Gal. < 2 < 75,000 Btu/hr or < 12 kw < 200,000 Btu/hr or < 12 kw 5
Impact: Categorization Delivered Efficiency, is strong function of daily hot water draw -> Lower capacity WHs will have lower rated EFs. Previously uncategorized products will go from Thermal Efficiency (TE) to EF, recent data show that a 95% TE condensing storage WH receives a 0.78 EF with the current MOT Delivered Efficiency versus Daily Heat Output (Btus) Kosar, D. et al. Residential Water Heating Program - Facilitating the Market Transformation to Higher Efficiency Gas-Fired Water Heating - Final Project Report. CEC Contract CEC-500-2013-060. (2013). 6
Hot Water Draw (gallons) Hot Water Draw (gallons) Impact: Draw Patterns Current MOT: 64 gal/day 12 10 8 6 4 2 0 Current MOT Draw Pattern, for all WHs, is known to over-estimate the efficiency of no/low-storage equipment. New MOT Medium Category: 55 gal/day 16 14 12 10 8 6 4 2 0 1.7 GPM 1.0 GPM Distributed draw patterns in the new MOT may result in rated changes of value between EF/UEF 7
Other Impacts Reduction of thermostat setting to 125 F Broadening scope, to include: Storage equipment with 2-20 gallons, covering a previously existing gap for these hybrids. Residential-duty commercial products, essentially products not covered currently but: use single phase power, do not produce water > 180 F, and do not require ASME Boiler/Pressure Vessel certification. 8
Test Plan Seven representative WHs tested to current and new MOT. Quantify difference in results for EF/UEF (and other parameters) and their impact on projected energy savings. Water Heater Type Rated FHR/Max. GPM* Revised SUT Daily Volume Non-condensing Storage (NCS) Condensing Storage Residential (CS-L) Condensing Storage Res. Duty Commercial (CS-H) 75 gal. > FHR > 51 gal. Medium (Derate for Low Usage Too) > 75 gal. High > 75 gal. High Non-condensing Tankless (NCT) > 4.0 gpm High Condensing Tankless (CT) > 4.0 gpm High Hybrid (H) > 75 gal. High Electric Heat Pump Storage (EHP) 75 gal. > FHR > 51 gal. Medium * Note FHRs/Max. GPM determined at new reduced thermostat setting 9
Change in UEF as Percentage of EF Test Results 125% 120% 115% 110% 105% 100% 95% 90% 85% 80% 75% 0 0.5 1 1.5 2 2.5 Tested EF of Water Heater Data show range of +/-20% change in UEF/EF, on par with what US DOE published previously. Impact of daily volume draw Standby recovery bias C/NCT NCS H CS EHP Tankless Heaters* Storage Heaters* *Water Heater Test Procedure Rulemaking: Development Testing Preliminary Report Energy Conservation Program for Consumer Products and Certain Industrial Equipment: Residential and Light Commercial Water Heaters, US DOE (2013) 10
UEF/EF and Recovery Efficiency UA (Btu/hr-F) Test Results 1.00 14 3.50 0.90 12 3.00 0.80 10 2.50 2.00 8 0.70 1.50 6 1.00 0.60 EHP 4 EF - Current MOT UEF - New MOT 0.50 2 nr - Current MOT nr - New MOT UA - Current MOT 0.40 NCT CT NCS-M NCS-L H CS-L CS-H EHP 0 UA - New MOT nr is η R, the recovery efficiency as calculated by the procedures 11
Test Results Why is UEF > EF except for NCS? Higher daily draw volumes increase impact of SS efficiency versus standby losses First draw volume of 15/27 gallons larger and, for Low/Medium Usage patterns, at 1.7 gpm, yielding higher recovery efficiency. Recovery efficiency also higher for units with slower recoveries (heat pumps), which can fully recover prior to end of hot water draws. Outlet temperature variation can bias UEF/EF. Both units not currently rated with EF experienced a standby recovery, biasing EFs lower 12
Percentage Adjustments in DHW Energy to Delivered Temperature Target Test Results Delivered Temperature Both MOTs adjust DHW output energy for delivered temperatures off-target. Like other adjustments (e.g. ambient conditions), the smaller it is (total and for each draw event), the more repeatable and accurate the results. 14.0% 12.0% 10.0% 8.0% 6.0% 4.0% 2.0% 0.0% -2.0% -4.0% New MOT Current MOT NCT CT NCS-M NCS-L H CS-L CS-H EHP 13
Average Delivered Temperature (F) Average Delivered Temperature (F) Test Results Delivered Temperature 145 140 135 130 125 120 115 110 105 145 140 135 130 125 120 115 110 105 Current MOT 1 2 3 4 5 6 Draw Number New MOT 1 2 3 4 5 6 7 8 9 10 11 12 13 14 14 Draw Number NCT CT NCS H CS-L CS-H EHP NCT CT NCS-M NCS-L H CS-L CS-H EHP
Simple Delivered Efficiency Test Results Draw Pattern 1 Overall test UEF and simple delivered efficiency show high degree of linearity. Despite range of delivered efficiencies for each on-cycle event. 0.9 0.8 0.7 0.6 0.5 y = 1.0429x - 0.0264 R² = 0.9846 0.4 0.4 0.5 0.6 0.7 0.8 0.9 1 Tested UEF of Water Heater 15
Simple Delivered Efficiency of Each On-Cycle Test Results Draw Pattern The range of delivered efficiencies for each oncycle event is high (without adjustments for change in stored energy). Impact of using an assumed constant recovery efficiency Impacts Higher UEF systems. Same magnitude error in quantifying recovery heat, disproportionately affects UEF of EHP vs. NCS by order of magnitude. 1 0.9 0.8 0.7 0.6 0.5 0.4 0 5 10 15 20 25 30 On-Cycle duration (min) 16 NCT CT NCS-M H CS-L CS-H
Temperature (F) Draw Rate (GPM) and Firing Rate (10,000 Btu/hr) Test Results Draw Pattern (Long) 130 120 CS-H 12 10 110 100 8 90 6 80 4 70 TC #1 TC #2 TC #3 60 TC #4 TC #5 TC #6 Avg Tank Inlet Outlet Draw Rate Firing Rate 50 12:00:00 AM 12:02:53 AM 12:05:46 AM 12:08:38 AM 12:11:31 AM 12:14:24 AM 2 0 17
Temperature (F) Draw Rate (GPM) and Firing Rate (10,000 Btu/hr) Test Results Draw Pattern (Short) 140 130 120 TC #1 TC #2 TC #3 TC #4 TC #5 TC #6 Avg Tank Inlet Outlet Draw Rate Firing Rate CS-H 12 10 110 8 100 6 90 80 4 70 2 60 50 0 4:27:50 PM 4:30:43 PM 4:33:36 PM 4:36:29 PM 4:39:22 PM 4:42:14 PM 4:45:07 PM 4:48:00 PM 4:50:53 PM 18
Efficiency Average Tank Temperature (F) Efficiency Average Tank Temperature (F) Test Results Draw Pattern 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Del. Eff. Avg. Rec. Eff. Starting Avg. Tank T CS-L 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 135 132.5 130 127.5 125 122.5 120 117.5 115 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Avg. Rec. Eff. Del. Eff. Starting Avg. Tank T 1 2 3 4 5 6 7 8 9 10 11 12 Draw Number NCS-M 19 135 132.5 130 127.5 125 122.5 120 117.5 115
Test Results Draw Pattern CT H CS-L CS-H EHP 0 200 400 600 800 1000 1200 1400 20
Market Implications For these data, where UEF < EF for baseline (NCS) but EF < UEF for all others, water heaters now may have shorter paybacks. Depending on local conditions, incentives for higher efficiency residential water heaters may make more sense where they may not currently. Further Challenge for Utilities: But what is baseline? Is it category specific or universal? Assuming High Usage draw patterns using measured EF/UEF values, all product types show improved economics with 2013 avg. utility prices. Reduction in Payback Period with New MOT Water Heater Type NY CA FL CS-L 42% 43.2% 38% CS-H 17% 17.6% 16% NCT 25% 25.4% 24% CT 9% 9.4% 9% H 33% 34.6% 28% 21
Conclusions Things to Look For Repeatability How do the distributed draw patterns impact repeatability of the test? How well are the short hot water draws characterized? Does the same test within the tolerances, ± 0.1 gal/draw (1 gpm/1 gal. draw), ± 2 F inlet, etc. yield the same on-cycle pattern? What s the baseline? With pending conversions for existing products, do consumers compare mid to mid usage products, high to high? Most common min. EF will be categorized as mid, most mid/high efficiency will be categorized as high, how to compare? 22
Questions & Answers @gastechnology 23