Steam humidifier annual maintenance checklist

Unit drained through its own cycle before lockout

Manual drain run from the controller so the tank or cylinder and its lines are empty, and any heated water or steam given time to cool before the unit is opened.

Power, control, gas or steam supply and water isolated and tagged

Every feed locked and tagged, water valved off. Before the safety tests: closed up and refilled, people clear, locks lifted by whoever hung them, then re-locked before hands go back in.

Cylinder replaced or tank descaled to bare metal

Disposable cylinder swapped, or the evaporating tank opened and descaled, electrodes or heaters cleared of the mineral shell that drops output and overheats the element.

Fill cup, level device and valves rebuilt or cleared

Fill cup, float or conductivity probe cleaned of scale, fill and drain valves rebuilt or cleared so water level and end-of-cycle drain are accurate again.

Terminals and heater, electrode or burner control wiring checked

Contactor or relay faces, terminals and heater, electrode or burner control leads free of pitting and heat marks, lugs torque-verified and re-torqued only where found loose.

Gas burner or steam-to-steam exchanger checked on those types

Gas-fired: burner, igniter, flue and combustion checked as the manufacturer directs. Steam-to-steam: exchanger, steam valve and trap checked for scale and leaks.

Wetted parts cleaned and disinfected to the hygiene procedure

Tank or cylinder housing, fill and drain piping and drain pan scrubbed of biofilm and flushed to the manufacturer's hygiene procedure, with no cleaning chemical left to reach the steam.

Feed water hardness or conductivity tested ahead of the unit

Supply sampled at a tap ahead of the isolation valve and compared with the manufacturer's limits for this type, any drift reported to the owner or the water treatment contractor.

Dispersion tube pulled, cleaned and absorption path checked

Tube removed and ports cleared, duct downstream checked for wetting or corrosion and the absorption distance still clear of coils, filters and turns.

Dispersion mounting, duct seal and duct drain checked

Tube or manifold brackets secure, the duct wall penetration sealed, and any duct drain pan below the dispersion flowing to its trap.

Building operator warned before the airflow and limit trips

Owner or building operator told before the air handler is stopped for the proving test, and users of any space with a critical humidity need told the unit goes offline.

High-limit, airflow proving and humidistat calibrated and tested

Duct high-limit and airflow proving switch functionally tripped to confirm they cut steam, humidistat compared against a reference reading and adjusted.

Water level and leak safeties seen to cut fill or output

High-water, low-water or leak safety for this type exercised as the manufacturer describes, fill or output seen to stop and the alarm shown on the controller.

Covers refitted, locks cleared and the unit run on a call

Cabinet and duct access panels closed, locks removed by whoever hung them, water and power restored, unit left in auto and making output on a real call.

Annual findings logged beside last year's service

Descale extent, parts renewed, water test result and each safety trip result entered so next year's service compares against them.