Maintenance & Reliability · SOP

Commercial Rooftop Unit RTU Preventive Maintenance & Filter Change

This procedure covers the systematic inspection, cleaning, and filter replacement of packaged commercial rooftop HVAC units (RTUs). Proper PM reduces energy consumption, extends equipment life, and maintains indoor air quality.

Estimated Time

45 min

Difficulty

Intermediate

Regulation

ASHRAE 62.1 / CSA F280

Version

1.0

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Purpose

To define a standardized, repeatable work process for performing preventive maintenance and filter replacement on commercial packaged rooftop units (RTUs). This SOP ensures that critical components — filters, coils, belts, electrical connections, condensate drains — are inspected and serviced at the manufacturer-recommended intervals, reducing unplanned downtime, maintaining manufacturer warranty conditions, and optimizing energy performance.

Scope

This SOP applies to all packaged commercial rooftop HVAC units rated between 3 and 20 tons that are installed on owned or leased industrial and commercial facilities. It covers single-zone, multi-zone, and VAV RTU configurations. This procedure does not include chillers, DX split systems, or residential units.

Safety Precautions

LOTOLock out and tag out the unit at the line-side disconnect switch. Verify zero voltage using a calibrated multimeter before opening any panels.
PPEWear safety glasses, cut-resistant gloves, hard hat, and slip-resistant footwear. Use a properly rated ladder for roof access; never climb on wet surfaces.
FALLIf roof height exceeds 3 m, use a personal fall arrest system (PFAS) anchored to a rated roof tie-off. Maintain 100% tie-off at all times near the unit.
ELECCapacitors retain charge. Discharge capacitors with a 20 kΩ resistor before handling. Use insulated tools on live electrical components.

Required Tools & Materials

Replacement air filters (correct size & MERV rating per O&M manual)
Filter gauge / manometer (0–2.5” w.c. range)
Vacuum cleaner with HEPA filter and crevice tool
Lockout/tagout kit (padlock, hasp, tag, group LOTO if applicable)
Socket set (3/8” drive, metric/SAE) and combination wrenches
Flathead and Phillips screwdrivers (insulated)
Multimeter (True RMS, CAT III rated)
Non-contact infrared thermometer
Coil cleaner (compatible with fin material) and spray bottle
Shop towels, disposable gloves, and trash bag
Ladder rated for roof access (Type IA or IAA)

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Procedure: Step-by-Step

1 Lockout/Tagout (LOTO) — Turn off the unit at the dedicated disconnect switch. Apply your personal lock and tag. Verify zero voltage at the contactor load side using a multimeter. Secure the roof ladder or roof hatch access.

2 Remove Access Panels — Using the appropriate screwdriver or socket, remove the supply air, return air, and filter access panels. Keep all fasteners organized in a parts cup. Set panels aside without damaging gaskets.

3 Inspect and Replace Filters — Use a manometer to measure static pressure drop across the filter bank before removal (baseline). Slide out old filters, vacuum filter tracks and door gaskets. Install new filters of the correct size and MERV rating (arrow pointing in direction of airflow). Reattach filter doors and tighten fasteners evenly.

4 Inspect and Clean Coils & Drains — Examine evaporator and condenser coils for dirt, fin damage, or microbial growth. Clean using no‑rinse coil cleaner and a soft brush if necessary. Flush condensate drain pan and line with water; confirm free drainage. Clear the trap and ensure it is primed to prevent air infiltration.

5 Fan & Motor Inspection — With power still locked out, check belt tension (1/2” deflection per foot of span) and alignment; look for cracks or glazing on the belt. Replace belt if worn. Lubricate fan motor bearings (if grease fittings are present) using lithium‑based grease per the motor nameplate. Hand‑rotate the fan wheel to check for balance and clearance.

6 Electrical System Check — Inspect contactor contacts, relay contacts, and capacitor(s). Tighten all power and control wiring terminal lugs to manufacturer torque specifications. Check for signs of overheating (discolored plastic, burnt insulation). Measure and record supply voltage and full‑load amp draw for each phase.

7 Reassemble, Restore Power, and Test — Reinstall all access panels and tighten fasteners. Remove LOTO tags and restore power. Start the unit and verify 5‑minute run cycle: measure ΔT across the unit (cooling: 15–20°F, heating: 30–40°F). Listen for abnormal noise or vibration. Confirm condensate drainage. Record all readings in the maintenance log (use ServiceGrid template).

Commercial Rooftop Unit RTU Preventive Maintenance & Filter Change

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