Maintenance & Reliability · SOP

Industrial HVAC Roof Top Unit (RTU) Filter Replacement

Standard procedure for replacing 2-inch pleated MERV-8 filters on packaged roof top units to maintain indoor air quality, equipment efficiency, and prevent excessive static pressure.

Estimated Time

40 min

Difficulty

Moderate

Regulation

WorkSafeBC / CSA Z317.1

Version

1.0

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Purpose

This procedure defines the approved method for replacing 2-inch pleated MERV-8 air filters in packaged roof top units (RTUs) at industrial facilities. Correct filter replacement maintains indoor air quality within regulatory limits, prevents fan motor overload due to excessive static pressure, and extends the service life of the heating/cooling coils. Compliance with this SOP ensures consistent airflow and energy-efficient operation of the HVAC system.

Scope

This SOP applies to all single-zone and multi-zone packaged RTUs rated between 5–50 tons installed in industrial buildings, warehouses, and workshops. It covers filter access, inspection, removal, disposal, and installation of new filters. It does not cover economizer damper adjustment, fan belt replacement, or coil cleaning operations. Tasks beyond filter replacement require a separate work permit and qualified HVAC technician.

Safety Precautions

LOTOLock out the RTU disconnect switch at the unit. Verify zero energy by attempting a start command from the thermostat or BMS override. Do not rely on remote shutdown alone.
PPEWear cut-resistant gloves (ANSI A4 minimum), safety glasses with side shields, and a NIOSH-approved N95 respirator when handling soiled filters. Replace respirator if moisture or damage occurs.
FALLIf the RTU is installed at a height ≥ 6 ft above grade, use a properly anchored safety harness and lanyard (CSA Z259.10). Ensure access platform or ladder is rated for industrial use.
BIOUsed filters may contain mould, bacteria, and respirable dust. Do not blow dust off filters. Seal immediately in a heavy-duty garbage bag. Dispose as per local environmental regulations.

Required Tools & Materials

Replacement filters (nominal 2" × 24" × 24", MERV-8 or equivalent — verify dimensions on existing filter label)
Flashlight (headlamp recommended)
Cut-resistant gloves (ANSI A4 minimum)
Heavy-duty garbage bags
Strap wrench (if filter retaining clips are seized)
Marker or label to record filter size and direction of airflow
HEPA vacuum cleaner with crevice tool (for debris removal in the filter rack)
Lockout/tagout kit (padlock, hasp, danger tag)
Safety harness and lanyard (if fall hazard exists)

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Procedure: Step-by-Step

1 Shut down RTU at the unit-mounted disconnect switch. Apply personal lockout/tagout device (padlock and danger tag). Confirm power is off by attempting a start command at the thermostat or BMS — the unit must not operate.

2 Remove the filter access panel. Most RTUs use hinged panels with quarter-turn latches or captured screws. Set the panel aside in a clean, dry area away from traffic.

3 Use a flashlight to locate the filter retaining clips or tracks. Note the airflow direction arrow printed on the existing filter (should point toward the blower). Mark the direction on the filter rack with a marker for reference.

4 Carefully withdraw the dirty filter(s) one at a time. Slide them straight out in the direction of airflow to minimise dust release. Immediately place each removed filter into a heavy-duty garbage bag. Close the bag tightly to contain contaminants.

5 Inspect the filter rack, gasket surfaces, and blower inlet for debris, mould, rodent droppings, or damage. Use a HEPA vacuum cleaner with crevice tool to remove any loose dust or contaminants. Do not use compressed air.

6 Insert the new filter(s) ensuring the orientation arrow points toward the blower (downstream). Engage retaining clips or tracks firmly. Verify the filter gaskets seat evenly against the rack to prevent bypass leakage.

7 Replace the filter access panel and secure all latches/screws. Remove the lockout/tagout device. Restore power to the RTU by closing the disconnect switch. Confirm normal unit operation: check for airflow at supply diffusers and listen for unusual noise.

8 Record the filter replacement date, new filter MERV rating, and any observed condition of the old filter on the maintenance log. Dispose of the sealed garbage bag containing old filters in accordance with facility waste management protocols.

Industrial HVAC Roof Top Unit (RTU) Filter Replacement

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