Fuel Cell Systems

Article 692 handles a quiet, solid-state kind of generation: a fuel cell converts chemical fuel directly to electricity through an electrochemical reaction. Electrically it behaves like another on-site source, so the article covers its output conductors, overcurrent, disconnecting means, grounding, and how it ties in when it runs in parallel with the utility or other sources.

The tricky part with any on-site source is making sure everyone knows it is there, so I am strict about the disconnects and the labeling that warns of a second source of power. A fuel cell can keep a service energized even when the utility is off, and the next person to work on that gear needs to be told, clearly, that it is not as dead as they think.

When it applies

Article 692 governs stationary fuel-cell systems, units that make electricity from hydrogen or natural gas through an electrochemical reaction. It deals with the electrical output side, the output circuit conductors, the disconnecting means, grounding, and how the fuel cell coordinates with the grid, batteries, or other on-site sources it parallels with.

Common mistakes

• Forgetting the fuel cell is a source that keeps producing, so it needs its own clearly marked disconnect like any other generator.
• Overlooking the interconnection and utility-interactive rules where the unit ties to the grid.
• Leaving the mechanical fuel-system safety interlocks out of the shutdown scheme.

In the field

I treat a fuel cell like any other always-on source, the electrical disconnect drops its output, but the fuel side has its own shutdown, and both have to be part of how you make the system safe. Killing the grid feed alone does not stop a stack that is still reacting.