Rooftop Package HVAC Operations and Maintenance Measures: David Baylon Stan Price Bob Davis

Rooftop Fundamentals Packaged air handler with heating and cooling source built in –Typically gas fired heating with compressor cooling –Economizer required by all regional codes for equipment above 5 cooling tons (less in some cases) –Building ventilation handled by the package unit with outdoor air introduced into the mixed air plenum Almost 80% of all HVAC systems use this sort of package technology Particularly important in small commercial and “big box” applications in suburban and exurban applications

Operational Issues Most economizers are assumed to provide up to half of the cooling requirement Surveys of economizer operation concluded that at least 50% are broken or not optimized Simple controllers, inaccurate sensors, and primitive dampers insure minimal functionality in many units. O&M contracts seldom extend to unit operation or efficiency

PSE Premium Rooftop Service Operated since 2003 with about 10 contractors Serviced about 2000 rooftop units Provided training for about 150 service technicians Focused on economizer and air flow Limited to units under 25 tons

Analysis Packages Package 1: Basic Service –Check thermostat type/settings –Measure economizer airflows; adjust as needed –Adjust economizer changeover temperature –Clean coils Package 2: Basic Service/Repair –Basic Service plus –Wire/enable morning warm-up control (heating savings) –Repair outside air or return air damper Package 3: Thermostat –Basic Service plus –Install two-stage cooling thermostat –Wire/enable morning warm-up control

Analysis Package (Cont.) Package 4: CO 2 Control –Basic Service plus –Add CO 2 sensor and needed economizer controller Package 5: Conventional controller –Basic Service plus –Replace economizer controller Package 6: Controller plus thermostat –Basic Service plus –Install 2 stage cooling thermostat and new econo. controller Package 7: New Economizer –Install new economizer on existing unit and –Perform Basic Service

Cost of Measures Cost Assumptions: Basic Service350 Thermostat200 Controller250 CO2/Controller600 Warm-up Relay100 Economizer1500 Assumes a 5-10 ton rooftop unit Annual maintenance normalized to a 5 year basic maintenance cycle Applied to 7.5 ton, 3000 sf zone

Assumptions Cooling equipment modeled at 8.3 EER Heating equipment efficiency square feet, 7.5 ton RTU (single zone operation and control) 20% Make-up air setting (Package 1,3,5,7) 30% Make-up air setting (Package 4,6) 50% Make-up air (Stuck damper, Package 2) 35% mixed air leakage (65% maximum outside air) LPD: 1.55 w/sf, office w/sf, retail Broken damper: stuck at 50% make-up No warm-up control 55 F economizer change-over

Seattle Office Package BaseTreatmentSavingsCostLifeO&M HeatingCoolingHeatingCoolingHeatingCooling kWh/sf $/sfyrs$/sf Basic Repair T-Stat DCV Control Reset New Econ

Boise, Office Package BaseTreatmentSavingsCostLifeO&M HeatingCoolingHeatingCoolingHeatingCooling kWh/sf $/sfyrs$/sf Basic Repair T-Stat DCV Control Reset New Econ

Seattle Retail Package BaseTreatmentSavingsCostLifeO&M HeatingCoolingHeatingCoolingHeatingCooling kWh/sf $/sfyrs$/sf Basic Repair T-Stat DCV Control Reset New Econ

Boise Retail Package BaseTreatmentSavingsCostLifeO&M HeatingCoolingHeatingCoolingHeatingCooling kWh/sf $/sfyrs$/sf Basic Repair T-Stat DCV Control Reset New Econ

Results Overall savings in Seattle are about 1300 kWh for cooling and about 40 Therms heating without repairs Repairs or CO 2 control increases heating savings by a factor of ten. Costs for Basic Service packages vary from $350 to $800 (higher cost includes thermostat and controller) Costs for CO 2 sensor plus needed controller with Basic Service is about $950