Transfer switch failure during generator changeover causes Montreal data centre outage
Nov 2010Published 13 Oct 2026Responsible editor: Chief Editor
Get the next one by email
Free alerts on data centre incidents in Canada, and an email when EIR-2326 is updated. No account needed; unsubscribe in one click.
Get a free sample brief Three complete verified records and the incidents-per-GW table, by email within a minute.
By signing up you agree to the privacy policy.
Companies named in this entry: iWeb
What happened
On the evening of 3 November 2010, a fire near an iWeb data centre in Montreal disrupted the utility power supply. The facility automatically switched to backup generators. Two of the three generators transferred normally. The third generator started, but the transfer switch did not transfer load to it as expected. About one third of the data centre, roughly 1.5 MW of load and around 3,000 servers, lost power. Most servers were restored about 2.5 hours after the outage began, but some customer servers remained down for up to 13 hours, into the afternoon of the following day.
The iWeb team said that the failure to transfer to the third generator was not understood at first, and that it was still investigating when it reported the incident.
Contributing factors
A nearby fire caused disruption to the utility supply, which triggered the changeover to generator power. The company suspected that the transfer switch control logic was disrupted by the fire-related power outage, but this had not been confirmed. Generator tests were carried out weekly, and a successful test had been completed the day before the incident with no signs of problems.
Lessons learned
- Test automatic transfer switches under realistic fault conditions, not only routine generator start tests, so that control logic failures during a utility loss are found before a real event.
- Ensure that every generator and transfer path is verified to pick up load after a utility failure, and monitor each path so that a single failed transfer is detected immediately.
- Plan for external events such as fires near the site that can disturb both utility supply and control circuits at the same time, and keep procedures to restore load manually when automatic transfer fails.
More lessons on maintenance, inspection and ageing assets, detection and monitoring, worker safety and safe systems of work, from every incident on the register.
Source
Other entries that name Montreal
Published 2026-10-13. Written from public reporting. Descriptive, not investigative. See the data accuracy disclaimer.
