Bpa rtu winter operation presented to rtug august 2010
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BPA RTU Winter Operation Presented to: RTUG August 2010. Presented by: Kathryn Hile, The Cadmus Group Howard Reichmuth, New Buildings Institute. Winter Analysis Overview. Improvements to analysis template Downloading and organizing data Fan operation – schedules Gas pack operation

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Bpa rtu winter operation presented to rtug august 2010

BPA RTU Winter OperationPresented to:RTUGAugust 2010

Presented by:

Kathryn Hile, The Cadmus Group

Howard Reichmuth, New Buildings Institute

Winter analysis overview
Winter Analysis Overview

  • Improvements to analysis template

  • Downloading and organizing data

  • Fan operation – schedules

  • Gas pack operation

  • Heat pump operation

  • Winter economizing (or cooling)

  • Additional opportunities

  • Lessons learned

Winter sample
Winter Sample

  • 45 serviced RTUs

    • 32 at 3 sites in Puget Sound area

    • 13 at 3 sites in Tri-Cities area

  • 4 baseline RTUs in Tri-Cities: serviced spring 2010

Analysis template improvements
Analysis Template Improvements

  • All winter data in one spreadsheet (at hour level)

  • Much smaller analysis files

  • Automation with SAS and VBA

  • Time series dynamic graph

  • Both SA min and SA max plotted in time series

Downloading and cleaning data
Downloading and Cleaning Data

  • HOBOlink

  • Visual Basic

  • SAS

  • Excel

Data preparation process
Data Preparation Process

  • Download zip file from HOBOlink with data from all HOBOs

  • Organize by HOBO

  • Create one file for each HOBO, based on power, one sheet for each two-week period

  • Import to SAS with keys for CT size, WattNode scale factor, fan low and fan high

Data preparation
Data Preparation

  • Calculate hourly and daily minimums, maximums, totals and averages

  • Export to Excel

  • Only full 24 hour days used to create energy signature

  • View data in hourly compressor map, dynamic time series and energy signature

Data collection issues
Data Collection Issues

  • Some (not many) sensors failed last winter, and four sites required troubleshooting to fix

    • Splitters

    • AC adapter – battery failure

  • Downloaded data

    • One site: two units had nonsensical data

    • One site: three sensors just disappeared from HOBOlink – result of the AT&T upgrades last fall?

Winter operation
Winter Operation

  • Schedules – fan ON or AUTO

  • Fan kW, duty, base load

  • Typical signatures

Fan mode on
Fan Mode = ON

  • Winter numbers similar to pilot data

Fan mode auto
Fan Mode = AUTO

  • Small sample

  • Fan kW very close; fan duty and base load differed

Gas pack signatures
Gas Pack Signatures

  • 24 of 32 energy signatures were as expected

  • 8 needed more investigation to understand performance

Gas pack typical signature 1
Gas Pack Typical Signature 1

  • Operates same set schedule each day

Gas pack compressor map
Gas Pack Compressor Map

  • Same RTU as previous slide

Gas pack typical signature 2
Gas Pack Typical Signature 2

  • Operates slightly longer at lower temperatures

Compressor map
Compressor Map

  • Same RTU, compressor map

Gas pack typical signature 3
Gas Pack Typical Signature 3

  • Two signatures – Monday – Saturday, and Sunday

  • Unit may have reached setback temperatures when average daily temperatures below 40

Gas pack findings
Gas Pack Findings

  • Fanpower calculated this winter was close to metered pilot data in almost all cases

  • Fanduty was close to metered pilot data in units with fan scheduled ON

  • Fanduty and base load were difficult to predict from summer metered data when fan ran in AUTO mode

Winter heat pump operation
Winter Heat Pump Operation

  • Heat pumps were trickier

  • Smaller sample, all at a notorious site

  • Units served either offices or fabrication (manufacturing) spaces

  • Four units did not have economizers

Heat pump typical operation
Heat Pump Typical Operation

  • Energy increases as temperatures decrease

  • Steeper slope than for cooling

Heat pump compressor map
Heat Pump Compressor Map

  • Same unit as previous slide

Heat pump findings
Heat Pump Findings

  • Typical heat pumps will have a second sloped line

  • Need summer data (spring was not warm enough) to connect winter and summer usage

  • Will use that to calculate and predict total annual energy use, not just cooling and fan

Winter economizing
Winter Economizing

  • Some units modulate dampers to take advantage of free cooling.

  • SA min and SA max track OAT

  • Three speed fan?

Heating to economizing
Heating to Economizing

  • Fan operates at different power when heating or economizing

Atypical performance
Atypical Performance

  • Balance point below the range of monitored temperatures

  • Cooling at low temperatures

  • Units serving the same space

  • Two units with bad data

Cooling at low temperatures
Cooling at Low Temperatures

  • Mechanical cooling at 25 degrees

Heating a m cooling p m
Heating a.m., Cooling p.m.

  • Two different max kW, at 3.5 kW, cooling (SA min at 55) and heating 4.5 kW (SA max at 90)

Economizer findings
Economizer Findings

  • Cooling at temperatures below 40 degrees. Why? Controls? Or dampers didn’t modulate because broken? Bad sensor? Comments? Significant savings opportunity?

  • Cooling in the 50-60 degree F. Could economizer changeover temperature be increased for additional savings?

  • Winter is a good (better than summer?) candidate for economizer savings

Preliminary annual signature
Preliminary Annual Signature

  • Winter:

    • Standard, flat gas pack

    • Standard, sloped – but could we just take an average and keep slope at 0?

    • Gas pack with two occupancy schedules

    • Heat pump – is this signature messier than it would be during summer cooling? TBD.

  • Atypical.

Next steps in research
Next Steps in Research

  • Draft annualized savings methodology with separate characterizations of annual operation for summer and winter

  • Data block interval analysis

  • Recommendations regarding fan schedule persistence

  • Additional persistence analysis

  • Measure life implications from the data

  • Updated M&V protocol recommendations

Web enabled thermostats
Web-Enabled Thermostats

  • Test the web-enabled thermostat as an M&V tool as a substitute for data-loggers

    • Data-friendliness?

    • How complete is it?

    • What does it look like?

  • Use the current analysis protocol and modify it for these data