ENGINEERING NOTE / CAPACITY

Capacity margin determines what happens after restoration.

Shortening a restart cannot remove a steady cooling deficit. Compare restored capacity, requested load and the heat left to remove.

Low Kah Yi · 2 October 2026 · Independent synthetic example

Restoration changes availability. Margin changes the next response.#

A cooling unit can return immediately and still leave too little heat removal for the requested load. With a 600 kW load and two 250 kW cooling units, restored capacity is 500 kW. The remaining 100 kW accumulates heat even after every component is available.

Change one assumption.#

The comparison above holds the load, fault and restart assumptions constant. Increasing each unit to 350 kW makes restored capacity 700 kW. The system can then remove more heat than the load produces, although heat accumulated during the failure still needs time to leave.

Open the exact example, inspect the final temperature and select Compare changes. Try faster restart first, then more cooling capacity. The original restart is already zero: shortening it cannot create missing capacity.

Read the service trade-off.#

A lower thermal peak can also occur when the load loses power and stops generating heat. Compare unserved energy alongside temperature. Reducing requested load changes the service delivered; it should not be presented as an equal-service improvement.

Use the boundary, not a rating.#

This constant-capacity heat balance uses an illustrative thermal mass, idealized switching and a 600-second horizon. It excludes equipment curves, spatial airflow and protection coordination. It is a way to inspect assumptions, not a facility sizing method. A recovery outside the horizon is reported as not observed.

Explore the Resilience Studio, inspect the model boundaries, or read the essay on consolidation and recovery for a separate example of dependency and recovery reasoning.