Reading your BMS alarm log: what the common faults mean

When we show up to a unit that's been acting up, the first thing we pull is the alarm log. A burner management system records why it shut down, and the pattern in those records usually points straight at the cause. Here's how to read the common ones.

Flame failure

The most common fault. The BMS lost the flame signal and shut the fuel. Sometimes that's a real flameout; just as often it's the system failing to provea flame that's actually burning — a dirty flame rod, a weak pilot, or a grounding problem. Recurring flame-failure faults are the classic repeat-lockout symptom.

High-temperature shutdown

The unit exceeded its high-temp limit, or a drifted thermocouple said it did. Could be a process issue, could be a sensor out of spec. Cross-check the reading against an actual temperature before you go chasing the burner.

Low or high fuel-gas pressure

The pressure switches tripped outside the window. Low usually means a supply or regulator problem; high can mean a regulator that's drifted or failed. Either way the flame won't stay stable, so the BMS won't let it run.

Ignition / pilot failure

The system tried to light and couldn't prove a pilot within the trial window. Look at the igniter, the pilot gas, and pilot position — it never got a good light to begin with.

Reading the pattern

One-off faults happen. The same fault, same time of day, same conditions — that's a root cause waiting to be found, and it rarely fixes itself with a reset. Understanding how the BMS proves a flame makes the log a lot easier to read. When the pattern won't resolve, that's our BMS service — we'll find the root cause instead of resetting it again.