Commercial RTU Service + Maintenance

Why this matters

Rooftop units (RTUs) are the workhorse HVAC for commercial buildings under 50,000 sq ft - strip retail, restaurants, small offices, medical, warehouse front-office. Service revenue. The commercial customer is more demanding than residential (uptime matters), more profitable (higher hourly rates), + more sticky (long-term service contracts). Techs who can confidently service RTUs unlock the highest-margin segment of HVAC.

Scope

Applies to:

• Package RTUs 3 - 25 tons (typical small commercial)
• Gas + electric heat (most common)
• Heat pump RTUs (growing share)
• Constant-volume + VAV configurations
• Curb-mount + slab-mount installations

Excludes: chillers + cooling towers + large central plant equipment (specialty work), VRF systems (different service model), residential split systems.

Required certifications + safety

• EPA Section 608 Type II, which covers high-pressure equipment and is what an RTU is. Universal only matters if you also work small appliances (Type I) and low-pressure chillers (Type III)
• OSHA 10 (general industry safety)
• Roof access training + fall protection. Servicing an existing building is general industry work, so the trigger is 4 ft under 29 CFR 1910.28, not the 6 ft construction figure, and the low-slope roof rules in 1910.28(b)(13) govern how close to the edge you can work with what protection
• Manufacturer-specific training (Trane, Carrier, Lennox, Daikin) recommended
• Some markets require commercial HVAC contractor license separately from residential

Annual PM scope (per RTU)

The standard preventive maintenance visit per RTU:

Pre-visit prep

1. Pull last service ticket; note recurring issues
2. Verify roof access (key, escort, fall protection set up)
3. Bring filter inventory (size + MERV per spec)
4. Bring belt + bearing inventory
5. Confirm power-down protocol with building manager

Inspection (15 - 30 min)

1. Visual: cabinet condition, refrigerant line insulation, condensate drain, electrical disconnect, gas piping
2. Outdoor coil: dirt accumulation, fin condition, hail damage
3. Condenser fan blade: balance, free rotation, cracks
4. Service panels secure
5. Disconnect locked OPEN before any internal work

Air handling section

1. Filter replacement (standard MERV 8 - 11; MERV 13+ on premium contracts)
2. Blower wheel: clean if grease/dust buildup; recommend coil-wheel clean if > 60% scaled
3. Belt: tension + wear inspection; replace if cracked OR > 1/3 worn
4. Pulleys: visual + alignment; check + tighten setscrews
5. Bearings: listen for grinding; lubricate where serviceable

Cooling section

1. Refrigerant pressures: high-side + low-side; compare to spec for ambient + load
2. Compressor amperage at full load: compare to nameplate
3. Capacitor reading (if accessible): bulge check + microfarad reading
4. Contactor: visual; pitted contacts = replace
5. Pressure switches + safety controls test
6. Subcooling + superheat measurements (if charge level questioned)

Heating section (gas)

1. Heat exchanger: visual inspection for cracks (mirror + flashlight; carbon monoxide test recommended)
2. Burner: clean orifices; verify clean blue flame
3. Igniter: HSI resistance check (typically 40 - 200 ohms cold) OR pilot inspection
4. Gas valve: 24V operation; manifold pressure verification
5. Flue: blockage check; combustion analyzer test recommended (CO target <100 ppm air-free)
6. Inducer motor + pressure switch

Heating section (electric)

1. Heat strip operation + amperage draw
2. Sequencer or relays
3. Limit switch operation
4. Element condition (resistance check on individual elements)

Heat pump specific

1. Reversing valve: solenoid energization in heat mode; valve seat
2. Defrost board + control: test defrost initiation
3. Outdoor coil: heat-mode operation (lower differential than cool mode)
4. Auxiliary heat staging

Controls + thermostat

1. Verify thermostat function (cooling + heating call)
2. Fan auto + on operation
3. Setpoint accuracy
4. Schedule programming (commercial often has time clock + economizer)
5. Communication to building management system (if applicable)

Documentation

• Photo of each section before + after
• Service record with measurements
• Recommendations log
• Customer acknowledgment signature
• Filed in CRM with photos

Common RTU failure modes

• Compressor failure: hot summer + dirty coils → high head pressure → compressor burn
• Capacitor failure: 5 - 10 year life; cause of 30%+ of cooling no-start calls
• Heat exchanger crack: 12+ year RTUs; safety-critical replacement
• Belt failure: 1 - 3 year life; preventive replacement on PM
• Drain pan corrosion + condensate overflow: water damage to ceiling tiles below = customer complaint + insurance claim
• Economizer damper stuck: increased energy bills + occupant discomfort

Service contract structure

For commercial RTUs, price the agreement per unit per year and state clearly what is included: the PM visits themselves (usually two, a cooling-season and a heating-season pass), filters and belts as consumables, priority response time, and a stated discount on any repair labor outside the PM scope. Refrigerant, compressors, and heat exchangers stay out of the base agreement and get quoted when they come up.

Multi-RTU customers get a volume discount; 5+ RTUs typically gets a 10 - 20% reduced rate per unit.

Energy efficiency consulting

Commercial customers care about utility bills. Recommend:

• Economizer operation verification (the #1 unaddressed energy waste)
• Variable speed drive on blower (if applicable)
• Setback schedule optimization
• Pre-cooling / pre-heating scheduling
• Demand response participation (utility programs)
• ENERGY STAR portfolio benchmarking

This shifts you from "service vendor" to "trusted advisor" - sticky customer relationship.

References

• ANSI/ASHRAE/ACCA Standard 180 (Inspection and Maintenance of Commercial Building HVAC Systems). ACCA Standard 4 is the residential counterpart, not this one
• ASHRAE Handbook (HVAC Applications)
• AHRI Standards 340, 360 (commercial unit certification)
• NFPA 54 (gas piping + appliances)
• Manuall internal: Annual HVAC System Maintenance, HVAC Pricing Strategy + Flat-Rate Book