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Commissioning: How Much Of A Good Thing?

Deciding to retrocommission is just the first step.

Last month this column addressed the question of what type of buildings make good candidates for retrocommissioning. This month I want to cover the retrocommissioning process itself. Just like new construction commissioning, it is very important for building owners to define what they believe retrocommissioning is when procuring the services of a retrocommissioning professional.

As practiced across the country, retrocommissioning is delivered with a variety of levels of rigor and time durations. The simplest approach appears to be a quick assessment of existing conditions and identification of low cost/no cost modifications focused on energy savings. Some utilities expect these projects to be complete in less than two months. At the other end of the spectrum are retrocommissioning studies that extend through at least one full year of evaluation of existing building systems performance under all load conditions, involve extensive energy modeling, and result in an in-depth report on existing operations and recommended modifications for energy savings and enhanced performance.

There is no right or wrong way to perform retrocommissioning, and the decision about how far to take it needs to be made by the building owner in light of his/her priorities, budget, building size and systems complexity. The following are guidelines based on three tiers of retrocommissioning that may assist building owners in customizing an approach that works for their particular building. This represents the low, mid, and high end points along a spectrum of levels of rigor and are not intended to dictate just three choices for building owners.

LEVEL A (Minimum)

  1. Review building systems documentation

    • Original drawings

    • Retrofit drawings

    • Operations & maintenance manuals

    • Historical utility records

  2. Perform one site visit

    • Interview operations staff

    • Visually inspect equipment, configuration, and condition

    • Cursory review of controls operations

  3. Retrocommissioning Report

    • Recommendations for maintenance or repairs to existing equipment

    • Recommendations for low cost/no cost energy conservation opportunities (ECOs)

    • Energy savings and payback analysis

LEVEL B (Medium)

  1. Review building systems documentation

    • All Level A documents

    • Test and balance reports

  2. Perform multiple site visits as necessary to perform the following tasks

    • All Level A tasks

    • Step-by-step testing of control system performance under all modes of operation

    • Measure selected air and water flows

    • Set up and collect trend logs from local data loggers or the existing building management system

  3. Retrocommissioning Report

    • Everything in a Level A report

    • Trend log analysis

    • Energy use profile

    • Recommendations and analysis of more complex or costly ECOs

LEVEL C (Maximum)

  1. Review building systems documentation

    • All Level B documents

  2. Perform multiple site visits

    • All Level B tasks performed over a longer evaluation period (at least one year to collect data on systems operation under all operating conditions)

  3. Retrocommissioning Report

    • Everything in a Level B report

    • Recommendations for capital improvements that significantly alter the commissioned systems (e.g., new energy recovery equipment, higher efficiency chillers, piping reconfigurations, etc.)

    • Measurement and verification plan for confirming energy savings following implementation of the recommended ECOs

In some areas of the country, the local utility may have a rebate program that defines the steps required to receive partial funding for a retrocommissioning study. In addition, most professional commissioning organizations have guidelines for existing building commissioning. These are all resources available to the facility owner when customizing the most appropriate scope and level of rigor for each building to be retrocommissioned.

 

Commissioning: Getting It Right

Engineered Systems, September, 2007

by
Rebecca Ellis, PE, LEED AP, CCP, CxA
President
Questions & Solutions Engineering
1079 Falls Curve
Chaska, MN  55318
rteesmag@QSEng.com