Volume 24, number 3, December 2010

Recommissioning?… Re what?

We are hearing more and more about recommissioning or overhauling a building’s mechanical systems. What does it involve? What kind of building? What are the benefits? This is what we will try to clarify here for you.

The concept of recommissioning has been gaining ground for about 15 years. This approach is emerging, especially in the United States, and is making more and more inroads in our markets. Principally, these measures apply to HVAC (heating ventilation and air-conditioning) systems.

In order to clarify what recommissioning is, let’s look at the distinctions between various definitions of this approach:

  • Initial start-up or commissioning: The initial start-up involves all the actions that lead to the building’s compliance with the plans and specifications and with the good practices of each trade involved. A final report is produced, giving the technical details that will serve as a base for the years to come for on-going maintenance of systems and for any later modifications.
  • Retroactive start-up or retrocommissioning: This is a kind of “tune-up” of buildings not subjected to an initial commissioning. It happens only once in the lifetime of a building and its aim is to optimize operating and maintenance efficiency. It does not seek to restore efficiency to the level targeted on initial commissioning, since the vocation of the building has evolved since its construction.
  • Overhaul or recommissioning: This is aimed at buildings that have undergone a commissioning or retrocommissioning. It is a systematic procedure for ensuring that the building is operating according to the initial design criteria or to current operating needs.

The principal systems involved in a recommissioning are the following:

  • Heating and air-conditioning
  • Building envelope
  • Controls
  • Lighting and back-up systems
  • Heat exchangers

The Practical Guide for Commissioning Existing Buildings1 recommends the following method for designing a recommissioning project:

  • Planning phase: Carry out an exhaustive examination of the building’s documentation and draw up the objectives for the project.
  • Investigation phase: Find deficiencies, evaluate the site and select the most cost-effective improvement options.
  • Implementation phase: Carry out the improvement work, verify and monitor.
  • Final phase: Prepare the final report and monitor performance.

What kind of building is suitable for such a procedure?

Generally, and without restricting ourselves, we are talking about buildings of more than 100,000 ft2 with a relatively modern control system and up-to-date maintenance systems, where no significant investment is planned for the HVAC systems, and where there are more than five years of historical records. Among other things, internal or external technical resources must be available to assist in the recommissioning activities.

As a yardstick only, here are just a few of the measures that may be included in a recommissioning:

  • Readjustment of fresh air flows
  • Verification of steam traps
  • Calibration of sensors
  • On/off control sequences of ventilation systems
  • Cleaning of exchangers, evaporators and boilers to maintain their efficiency
  • Verification of temperatures of hot and chilled water loops

What is the energy impact of an intervention like recommissioning?

Impacts in the order of 5-15% have been reported in buildings where this procedure has been implemented. However, prudence is cautioned in applying these results directly. A more thorough study will help determine the best ways of optimizing the operation of a given building.

Next January, a program for recommissioning
a building’s mechanical systems is going to be
added to Gaz Métro’s Energy Efficiency Programs.

Marc Beauchemin, Eng. CEM

1. Haasl T. et T. Sharp, A Practical Guide for Commissioning Existing Buildings, Portland Energy Conversation Inc. PEIC, April 1999.