VRF Applications in PNW

RTF RTUG MeetingOctober 26, 2011

Kevin CampbellReid Hart, PE Technical Research Group

Modeled Office Building

Basic Qualities Simulation Runs1. RTU, no economizer2. RTU, with Economizer and

fan control3. VRF, Heat Pump, no

Economizer4. VRF, Heat Recovery no

Economizer

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Floors 2

Floor Area 25,000sq ft

Ventilation Rate 15cfm/person

Lighting Density 1.2watts/sq ft

Equipment Density 1.0watts/sq ft

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System ParametersRTU VRF

System RTU VRFSEER/EER SEER 13Cooling COP 3.99 3.96Heat AFUE (gas) 80.6% - Heating COP (HP) - 4.06Supply Fan Eff. (total) 36% 60%Supply Fan total SP 2.00 1.00DOAC total SP - 2.25DOAC Fan Eff. (total) - 53%

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Impact of VRF on HVAC Energy

• Fans have significant savings! (even more if no RTU fan control)• Heating savings in northern climates (switch gas to Electric)• Cooling savings except PNW where OSA economizer wins• Both cooling and heating benefit from variable compressor

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Small Office ComparisonTwo Models in PNW

• Duct leakage: ES high; PECI none• Separate ventilation fan: PECI 2.5”’; ES ?• ES: refrigerant piping loss factor; PECI none

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PNW Office Energy End Use Comparison

*PECI small office utilizes economizer and fan controls. Energy Solutions small office includes duct leakage.

Differences AreNot SuprisingA simple fan VSD measure had a wide range of savings when load variation was considered.

Differences indicate need for:• Regional standard buildings• Range of loads to capture variation• Expected value savings or other process to generate

population values

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Modeled Medical Clinic

Basic Qualities Simulation Runs1. VAV (dX) Electric Reheat +

Economizer + SAT reset2. VRF Heat Pump 3. VRF Heat Recovery

Building • Patient rooms with variable

occupancy• More perimeter zones• Diagnostic equipment room

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Floors 1

Floor Area 20,000sq ft

Ventilation Rate 20cfm/person

Lighting Density 1.2watts/sq ft

Equipment Density 1.0watts/sq ft

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Impact of VRF on HVAC Energy

• Fans have significant savings! • Heating always savings since no reheat with VRF• Cooling savings due to improved part load efficiencies and

high cooling requirements of VAV reheat

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Healthcare/Medium Office (VAV) Compare Two Models in PNW

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PNW Office VRF Energy Use per SF

*PECI VAV with electric reheat and SAT reset. Energy Solutions VAV with electric reheat.

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Other Heat Recovery Options:Domestic Hot Water

VRF Water Heater• Standard to 115°F • Booster to 160°FApplicable for buildings with both:• Heat rejection (server; equipment; kitchen; cooling)• Hot Water Load (Restaurants, Dorms, Hotel, Medical)Efficiency Improvement• VRF water heating percentage savings vs. gas

Water Heat Mode % Site Btu’s % MW/NE CostHeat Pump 80% 8%

Heat Recovery 93% 69%

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Exhaust Air Heat RecoveryAdapt the old run- around or loop heat pump concept• In heat mode, cool

exhaust air• In cool mode, heat

exhaust air• Feed general loop or

pre conditioning at DOAC

• Need to verify airside pressure tradeoffs

• This strategy not in models

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Conclusions• Modeling tools and load/system assumptions have

significant impact on predicted savings• VRF systems can provide significant HVAC savings

with lower fan energy and better part load efficiencies• Buildings with low heating loads in economizer friendly

climates have less significant savings• Exhaust and DHW heat recovery applicableNotes:• Proper control set-up & commissioning is important, as

simulations are based on perfect control operation• Simulations are not monitored results

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Questions?

Contact:Kevin CampbellPECIkcampbell@peci.org503-575-4169