The Chiller That Fails at Peak
A 12-story mixed-use building has two 400-ton centrifugal chillers, N+1 by design. Chiller B has failed its last two vibration analyses and the OEM recommends a compressor overhaul costing $180,000 with a 10-week lead time. Chiller A is 14 years old and running at 92% of design capacity on the hottest afternoons. The building's leases guarantee cooling to 24°C during occupied hours, and a data-center tenant on floors 11–12 has a contractual uptime clause with penalties of $5,000 per hour. Summer peak is six weeks away. The owner's capital committee meets monthly and has $250,000 of unallocated reserve.
1. Assess the risk and recommend a course of action to the capital committee.
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The building is effectively N=0, not N+1. With B down for a 10-week overhaul, A becomes a single point of failure at the worst possible time - peak season, when it is already at 92% of capacity and has no margin.
The risk is asymmetric. Overhaul cost is $180,000. A single eight-hour data-center outage at $5,000/hour is $40,000, and a multi-day failure during a heat wave could exceed the overhaul cost several times over, plus breach of the general cooling covenant across ten floors.
Recommendation: authorize the overhaul immediately, but do not rely on the overhaul alone to cover peak. In parallel, secure temporary cooling capacity - rental air-cooled units or a portable chiller tied into the data-center loop - for the six-week peak window. Budget the rental at roughly $30,000–$60,000 for the period; this fits within the $250,000 reserve alongside the overhaul.
Also commission an immediate condition assessment of Chiller A to confirm it can carry the load, and stage the overhaul so B is back online before the following summer at the latest. Present the committee with the exposure figure, not just the repair quote.
2. The capital committee defers the decision for one month to await more quotes. What do you do in the interim?
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A one-month deferral consumes most of the pre-peak window and pushes the overhaul start into the hottest period, which is the worst time to have B offline. Treat the deferral as a risk the committee has chosen, and manage it explicitly.
Interim actions: (1) Issue a written risk memo to the committee and owner documenting the exposure, the deferral, and the decision-maker, so accountability is clear. (2) Lock in the temporary cooling rental now with a reservation, so capacity is available regardless of the overhaul decision. (3) Ask the OEM to hold the overhaul slot and quote a firm price, and solicit the second quote from an independent service provider in parallel rather than sequentially. (4) Tighten Chiller A monitoring - daily logging, condenser cleaning, and a pre-peak performance test - to catch degradation early. (5) Brief the data-center tenant on contingency measures without disclosing the full commercial picture, and confirm the building's emergency cooling procedures.
Bring the committee a decision-ready package at the next meeting: firm quotes, rental reservation, and a dated schedule showing the last safe start date for the overhaul.