HVAC preventive maintenance checklist: what to record on every PM.

Identify the unit first.

Start at the nameplate, not the work order. Make, model and serial come off the plate. Shoot it and read it out loud. The office copy is often from the last swap, and nobody updated it.

Count the filters and take the size off the frame, not from memory. Take the belt size off the belt while the print is still legible. Take refrigerant type and factory charge off the plate. If the plate is painted over or gone, say so and use the site's tag for the unit.

Readings that belong on the sheet.

A PM without numbers is a wipe-down. Record what you would want if you came back in six months and the unit was down. A commercial rooftop and a residential split differ at the edges. The core is the same.

• ΔT across the evaporator coil, return to supply, in °F.
• Suction and head pressure in psig after fifteen minutes of run time, with the outdoor temperature beside them.
• Superheat and subcooling against the target on the plate or the charging chart.
• Total external static pressure with the filter in, and the filter condition next to it.
• Compressor and fan motor amps against RLA and FLA from the nameplate.
• Capacitor µF as read against the rating printed on the can.
• Belt condition, tension and sheave alignment on a belt-drive blower. Blower wheel condition on everything.
• Condensate drain: flowing, cleared, or trap missing.
• Coil condition before and after cleaning, condenser and evaporator.
• Economizer and gas section on an RTU. Heat strips or furnace on a split, when the season calls for it.

A number without a unit is a guess. A number without the rated value beside it sends the office to the manual.

Done, recommended, or open.

Every line on the sheet ends in one of three states. Done means you did it today and a reading or photo shows it. Recommended means the unit runs, you see a problem coming, and the customer decides. Open means the work is needed, not finished, and someone owns the next step.

Keep them apart. A cracked belt you could not replace is open, not recommended. A pitted contactor that still pulls in is recommended, not open. Put the part size and the owner on every open item. “Belt A42, order, swap next visit” reads in two seconds.

Photos that earn their place.

Five photos cover most PMs. The nameplate. The filter before you pull it, size showing on the frame. The belt, close enough to see the cracks. The drain where it leaves the pan. The finished unit with the panels back on.

Add one for anything you mark open or recommended. Shoot the gauge when a reading is out of range. One wide shot places the unit. Every other photo should answer one question.

One record per unit on a multi-unit roof.

Fourteen units on one roof is fourteen reports, not one long one. Each unit gets its own nameplate, its own readings and its own open items. The office bills and schedules by unit.

Say the tag as you walk. “Moving to RTU-05” closes one record and opens the next. Use the site's tags, not the one you make up on the ladder. If two units sit side by side with no tag, mark them before you start and say which is which.

The sign-off.

The tech fills the sheet. The lead reads it against the photos and signs it. The office sends it, and the customer gets a PDF with the readings, the photos and the open items. Three people, three jobs. Nobody skips theirs because the draft reads well.

Ten-4 drafts the sheet from what you say and shoot on the roof. The lead still checks the serial against the plate and the readings against the gauges.

Our fictional sample is a PM on RTU-04, west roof. Nameplate: model RT-1200, S/N J739281-A. Filters: two 20x25x2 pleated, replaced. Readings: ΔT 18°F, suction 118 psig. Run cap reads 38 µF on a 45 rated, replaced. Drain cleared, condenser coil rinsed. Belt A42 cracked, none on the truck. That one stays open: order the belt, swap on the next visit. Checked by M. Reyes, lead tech. PDF to the property manager.