Reading a controller alarm: a triage sequence for operators

An alarm is information, not a verdict. Most alarms on a well-commissioned controller are caused by something upstream of the controller: flow, sample line, probe condition, chemical supply, or the pool itself. Work through causes in this order before changing setpoints.

1. No-flow alarm

• Confirm the recirculation pump is running and the filter is not in backwash.
• Check the sample line to the flow cell for a closed valve, a clogged strainer, or air.
• Verify the flow switch or flow sensor is clean and seated.
• Feed should be locked out while flow is absent; this is the interlock doing its job (see 10 NYCRR 6-1.29 item 11.7).

2. Feed-limit (failsafe timer) alarm

• The controller fed for its maximum allowed time without reaching setpoint. First question: did chemical actually reach the water?
• Check chemical supply: empty tank, empty hopper, closed valve, air-locked pump, or a feeder that has stopped eroding.
• Check for a sample-line problem that leaves the probes reading stale water.
• Only then consider whether demand genuinely exceeded feed capacity (a heavy event, a large fresh-water addition).

3. Out-of-range pH or ORP/chlorine

• Confirm with a manual DPD and pH test; New York requires manual testing regardless of the controller (6-1.11).
• If manual and controller disagree, clean and recalibrate the probe per the manual, or replace a probe past its service life.
• If they agree, treat the water: the controller is telling you the truth.

4. Communication or remote-access alarm

• The controller keeps controlling locally. Check the network cable, switch, and internet connection before anything else.
• Remote visibility returns when the connection does; local logging continues in the meantime.

Record the alarm, the cause you found, and the action taken in your daily operation record. Patterns across weeks are the most valuable maintenance information you have. If an alarm recurs and you cannot find the cause, request service; do not raise the limit to silence it.