3/4/2014 Advanced RTU Control Strategies Ryan R. Hoger, LEED AP 708.670.6383 [email protected] Environmental Impact of Buildings* • 40% of total U.S. energy consumption • 39% of total U.S. CO2 emissions • 72% of total U.S. electricity consumption *Commercial and Residential 1 3/4/2014 Environmental Energy Impact of Buildings 100% USA Energy Consumption (BTU) 38.2% 28% Transportation 33.4% 32% Industry 28.3% 40% Buildings* Residential & Commercial Buildings 2010 DOE Buildings Energy Data Book 20.26 Quadrillion BTU Site > dropped to 19.99 in 2011 39.29 Quadrillion BTU Primary > means bldgs are about 51-52% efficient in terms of raw energy utilization Commercial HVAC Energy Consumption 27% of all commercial HVAC energy is used by fans!!! 2 3/4/2014 Efficiency Ratings for RTUs • Air-Conditioning, Heating, and Refrigeration Institute RTUs < 65,000 Btuh (~5.4 tons) • Use residential test standards • SEER •AFUE • RTUs >= 65,000 Btuh (~5.4 tons) • EER + IEER • Thermal Efficiency 3 3/4/2014 Industry Movement to IEER Ratings The industry and governing bodies are evolving to Integrated Energy Efficiency Ratio (IEER) values as the leading energy measure: - IEER models building part load profile – EER measures peak unit performance that is typically experienced 3% of the operating time. - Codes now specify both a minimum EER and IEER - Rebate programs generally specify just a part load min IEER - The Department of Energy (DOE) Rooftop efficiency challenge - ONLY specifies IEER @ 18.0 – NO EER ASHRAE 90.1-2010 & IECC 2012 Minimums 4 3/4/2014 ASHRAE 90.1-2013 Minimums Example Manufacture Product Offering High Tier IEER’s Nearly 70% more efficient than entry level Includes: up to 3 stage Nearly 50% more cooling, VFD supply fan, and efficient than mid- ECM condenser fan tier SEER / IEER SEER / High Efficiency Mid-Efficiency Code Tier Tier Minimum RTU Values are averaged 5 3/4/2014 Retro-commissioning Most Common* Improvements *DOE / Lawrence Berkley National Lab Study 2009 Retro-commissioning Savings for Key Improvements** **DOE / Lawrence Berkley National Lab Study 2009 6 3/4/2014 RTU Study Results* *2004 Study by New Buildings Institute 503 RTUs at 181 Sites Example RTU Tune-up Checklist 7 3/4/2014 2013 DOE Study: Advanced Rooftop Control (ARC) Retrofit: Field-Test Results • Pacific Northwest National Labs • Published July 2013 • Purpose was to study combined energy effects of an economizer, demand controlled ventilation, and multi-speed fan control for RTUs • Field testing done on 66 RTUs on 8 different buildings • Various occupancy types (retail, office, food, and healthcare) • Various climates • Mix of Carrier (32), Trane (21), and Lennox (13) units • Range of RTU sizes, but most (43) were 10 to 15 tons • Data collected on 1 minute intervals for 12 months • Controls were alternated between standard (pre-retrofit mode) and advanced control modes on a daily basis 2013 PNNL Study Key Findings • An initial study showed gas/electric units saved between 24 and 35% energy and heat pumps saved 20 to 60% • The field data from the 66 RTUs showed a savings range of 22 to 90%, with a 57% savings average for all RTUs • Fan energy savings was the dominant contributor of the savings • Average payback periods were 6, 3, and 2 years for the 3 utility rates ($0.05, 0.10, and 0.15 / kWh) • Cost included both materials and labor • Larger units and longest runtime units had the shortest paybacks, as expected 8 3/4/2014 Products Reviewed • Available retrofit products: • Transformative Wave’s CATALYST • Enerfit • Bes-Tech’s Digi-RTU Optimizer • All 3 vendors retrofit supply fans with a VFD and generally change speed based on mode (heat, cool, vent, etc.) • All 3 also provide airside integrated economizer controls and CO2-DCV capabilities • Digi-RTU also provides the ability to modulate compressor speed • Based on product maturity and availability, PNNL choose to use the CATALYST product in the field testing PNNL Field Test Settings • Vent mode fan speed = 40% • Cool/heat speed = 75 or 90% (depending on # of stages) • CO2 high setpoint = 1,000 PPM 9 3/4/2014 PNNL Recommendations PNNL Study Runtime Examples 10 3/4/2014 Programmable Thermostats Programmable Thermostats • Stop running heating/cooling 24/7!!! • Relaxes heat/cool setpoints when space not occupied – Only setback about 5º (use 65º for heat and 80º for cooling) – Need to setback minimum of 6 hours to be effective • On average saves 25-30% on heat/cool energy* – If installed in every home would save about 5% of total US energy consumption* *John Hopkins Univ. AICGS Policy Report 11 3/4/2014 Programmable Thermostat Study Results* • Residential stats responsible for 11% of total US energy • What kinds of stats do people have? – 14% have no stat at all – 56% non-programmable – 30% programmable • Of those with programmable stats… – 89% have rarely or never programmed a stat – Only 30% of programmable stats are actually programmed – In winter, 60% use for night setback, only 45% setback during day – In summer, 55% use for night, same for day time – 2003 Carrier study also revealed that 53% of prog stats were in “hold” *2010 - DOE, EPA, and Lawrence Berkley National Labs Study Programmable Thermostats • Easy to retro-fit • Adaptive Intelligent Recovery • 2-stage stat for integrated economizer as 1st stage • Shut off ventilation during unoccupied hours • Internet accessible • Payback less than 6 months *John Hopkins Univ. AICGS Policy Report 12 3/4/2014 Internet Thermostats • Low cost alternative to BAS • Ethernet or Wi-Fi • No PC software – uses standard web browser • No access fees • Text/email alerts Internet Thermostats 13 3/4/2014 Internet Thermostats Phone Apps for Thermostats 14 3/4/2014 Economizers Outdoor Air Economizers • Use outside air for “free cooling” instead of compressors • 3 main types of control – Dry-bulb Temperature (enable when OA < 60º) – Enthalpy (enable when OA < 70º and humidity low) – Differential Enthalpy (is OA better than RA?) 15 3/4/2014 Outdoor Air Economizers • Integrated economizer – Economizer assists compressors on certain days • Building pressure relief needed • Occupancy control – Open to ventilation position only when building occupied (interlock to time clock of stat) instead of whenever fan on • Payback less than 6 months Barometric Relief Outdoor Air Intake Barometric Relief Section 11 – Options and Accessories 16 3/4/2014 Powered Exhaust Remote Duct Mounted Powered Exhaust Outdoor Air Intake Unit Mounted Powered Exhaust Section 11 – Options and Accessories IECC 2012: Commercial Economizers IECC 2012 already required by 8 states Also additional requirements for relief/exhaust, integrated economizer, types of economizer control, water-side economizers, etc. 17 3/4/2014 Existing Economizer Optimization • Many systems have never been commissioned at all – Perform functional performance tests • Economizer dampers and controls inoperative or in poor condition – Test bi-annually - repair or replace • Sensors not recalibrated on regular basis (especially enthalpy and CO2 sensors) – Recalibrate sensors bi-annually • Other issues: – Systems have been locked out by operator – Scheduling is not optimized (sometime running 24/7) – Economizer control not optimal (too high of OA setpoint) Insuring Proper Economizer Operation • Eliminate outside air for ventilation during unoccupied periods by closing OA dampers • OA damper operation should be monitored and recorded to verify actual operation of economizer • Percent OA can be used to verify that the economizer is properly operating • Percent of OA is calculated using a formula or graph 18 3/4/2014 OA% Calculation OA% = (MAT – RAT) (OAT – RAT) Example: OAT = 10° RAT = 70° MAT = 50° OA% = (50 – 70) = 33% (10 – 70) “Typical” Honeywell W7459 M7415 Economizer Economizer Logic Module Actuator Depending on sensors used, it is capable of dry-bulb changeover, enthalpy changeover, or differential enthalpy. Not capable of demand controlled ventilation (DCV). 19 3/4/2014 Honeywell W7212 Also capable of Demand Controlled Ventilation (DCV) Honeywell W7212 20 3/4/2014 Honeywell Logic Modules Honeywell Economizer Simulator customer.honeywell.com/economizertools 21 3/4/2014 Outdoor Air Dry-Bulb Economizer 60° F Outdoor AAir Temp 75° F db / 50% rh Compressor OFF Compressor ON Economizer ON Economizer OFF Modulate OA / RA / Exh. Outdoor Air Damper Section 11 – Options and Accessories at Ventilation Position Outdoor Air Enthalpy Economizer 65° F Outdoor AAir Temp 75° F db / 50% rh h = 25 Compressor OFF Compressor ON Economizer OFF Economizer ON Outdoor Air Damper Modulate OA / RA / Exh. Section 11 – Options and Accessories at Ventilation Position 22 3/4/2014 Integrated Economizer Compressor OFF Compressor ON Compressor ON Economizer ON Economizer OFF Economizer ON Outdoor Air Damper Outdoor Air Damper SectionModulate 11 – Options OA /and RA Accessories / Exh. Fully OPEN at Ventilation Position A, B, C, and D Enthalpy Curves Above Curves: Compressor ON Economizer OFF Outdoor Air Damper at Ventilation Position 75° F db / 50% rh Below Curves: Compressor OFF Economizer ON Modulate OA / RA / Exh. Section 11 – Options and Accessories 23 3/4/2014 CO2-based Demand Controlled Ventilation (DCV) Ventilation Control How is ventilation provided in buildings today? The same way it was in 1930. With Fixed Ventilation! 24 3/4/2014 Minimum Ventilation Rates Fixed Ventilation Building codes require ventilation rates based on cfm/person: (typically 20 cfm/person) MaxActual Occupancy: Occupancy: 25 51 people peopleperson = == 500cfm 500cfm500cfm Inefficient!