Rooftop Package HVAC

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Rooftop PackageHVAC

• Operations and Maintenance Measures
• David Baylon
• Stan Price
• Bob Davis

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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

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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.
• OM contracts seldom extend to unit operation or
  efficiency

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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

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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

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Analysis Package (Cont.)

• Package 4 CO2 Control
• Basic Service plus
• Add CO2 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

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Cost of Measures
Cost Assumptions Cost Assumptions
Basic Service Basic Service 350
Thermostat Thermostat 200
Controller 250
CO2/Controller CO2/Controller 600
Warm-up Relay Warm-up Relay 100
Economizer Economizer 1500

• 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

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Assumptions

• Cooling equipment modeled at 8.3 EER
• Heating equipment efficiency .80
• 3000 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. 3.05 w/sf, retail
• Broken damper stuck at 50 make-up
• No warm-up control
• 55 F economizer change-over

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Seattle Office
Package Base Base Treatment Treatment Savings Savings Cost Life OM
Package Heating Cooling Heating Cooling Heating Cooling
Package kWh/sf kWh/sf kWh/sf kWh/sf kWh/sf kWh/sf /sf yrs /sf
Basic 5.01 1.43 5.01 0.95 0.00 0.48 0.12 15.00 0.02
Repair 9.56 1.14 4.65 0.95 4.92 0.19 0.15 15.00 0.02
T-Stat 5.01 1.43 4.65 0.95 0.37 0.48 0.22 15.00 0.02
DCV 6.46 1.37 2.13 0.95 4.34 0.42 0.32 15.00 0.02
Control 5.01 1.43 4.65 0.95 0.37 0.48 0.20 15.00 0.02
Reset 6.46 1.38 4.65 0.95 1.82 0.43 0.27 15.00 0.02
New Econ 5.01 1.61 4.65 0.98 0.37 0.63 0.62 15.00 0.02
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Boise, Office
Package Base Base Treatment Treatment Savings Savings Cost Life OM
Package Heating Cooling Heating Cooling Heating Cooling
Package kWh/sf kWh/sf kWh/sf kWh/sf kWh/sf kWh/sf /sf yrs /sf
Basic 6.79 2.32 6.79 1.90 0.00 0.42 0.12 15.00 0.02
Repair 12.99 2.31 6.43 1.90 6.57 0.42 0.15 15.00 0.02
T-Stat 6.79 2.32 6.43 1.90 0.37 0.42 0.22 15.00 0.02
DCV 8.82 2.34 2.92 1.80 5.90 0.54 0.32 15.00 0.02
Control 6.79 2.32 6.43 1.90 0.37 0.42 0.20 15.00 0.02
Reset 8.82 2.38 6.43 1.90 2.40 0.48 0.27 15.00 0.02
New Econ 6.79 2.38 6.43 1.85 0.37 0.53 0.62 15.00 0.02
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Seattle Retail
Package Base Base Treatment Treatment Savings Savings Cost Life OM
Package Heating Cooling Heating Cooling Heating Cooling
Package kWh/sf kWh/sf kWh/sf kWh/sf kWh/sf kWh/sf /sf yrs /sf
Basic 1.83 3.69 1.83 2.50 0.00 1.19 0.12 15.00 0.02
Repair 6.32 3.08 1.76 2.50 4.56 0.58 0.15 15.00 0.02
T-Stat 1.83 3.69 1.76 2.50 0.07 1.19 0.22 15.00 0.02
DCV 3.56 3.73 0.72 2.41 2.84 1.32 0.32 15.00 0.02
Control 1.83 3.92 1.76 2.50 0.07 1.42 0.20 15.00 0.02
Reset 3.56 3.73 1.76 2.50 1.80 1.23 0.27 15.00 0.02
New Econ 1.83 4.30 1.76 2.53 0.07 1.77 0.62 15.00 0.02
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Boise Retail
Package Base Base Treatment Treatment Savings Savings Cost Life OM
Package Heating Cooling Heating Cooling Heating Cooling
Package kWh/sf kWh/sf kWh/sf kWh/sf kWh/sf kWh/sf /sf yrs /sf
Basic 2.38 4.64 2.38 3.79 0.00 0.85 0.12 15.00 0.02
Repair 7.17 4.50 2.31 3.79 4.86 0.71 0.15 15.00 0.02
T-Stat 2.38 4.64 2.31 3.79 0.07 0.85 0.22 15.00 0.02
DCV 4.26 4.99 1.24 3.66 3.02 1.33 0.32 15.00 0.02
Control 2.38 5.09 2.31 3.79 0.07 1.30 0.20 15.00 0.02
Reset 4.26 4.99 2.31 3.79 1.95 1.20 0.27 15.00 0.02
New Econ 2.38 5.29 2.31 3.78 0.07 1.51 0.62 15.00 0.02
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Results

• Overall savings in Seattle are about 1300 kWh for
  cooling and about 40 Therms heating without
  repairs
• Repairs or CO2 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 CO2 sensor plus needed controller with
  Basic Service is about 950