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 minimum for split + Type Universal for any commercial)
- OSHA 10 (general industry safety)
- Roof access training + fall protection (6+ ft fall = required harness OR guardrail per OSHA 1926.501)
- 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
- Pull last service ticket; note recurring issues
- Verify roof access (key, escort, fall protection set up)
- Bring filter inventory (size + MERV per spec)
- Bring belt + bearing inventory
- Confirm power-down protocol with building manager
Inspection (15 - 30 min)
- Visual: cabinet condition, refrigerant line insulation, condensate drain, electrical disconnect, gas piping
- Outdoor coil: dirt accumulation, fin condition, hail damage
- Condenser fan blade: balance, free rotation, cracks
- Service panels secure
- Disconnect locked OPEN before any internal work
Air handling section
- Filter replacement (standard MERV 8 - 11; MERV 13+ on premium contracts)
- Blower wheel: clean if grease/dust buildup; recommend coil-wheel clean if > 60% scaled
- Belt: tension + wear inspection; replace if cracked OR > 1/3 worn
- Pulleys: visual + alignment; check + tighten setscrews
- Bearings: listen for grinding; lubricate where serviceable
Cooling section
- Refrigerant pressures: high-side + low-side; compare to spec for ambient + load
- Compressor amperage at full load: compare to nameplate
- Capacitor reading (if accessible): bulge check + microfarad reading
- Contactor: visual; pitted contacts = replace
- Pressure switches + safety controls test
- Subcooling + superheat measurements (if charge level questioned)
Heating section (gas)
- Heat exchanger: visual inspection for cracks (mirror + flashlight; carbon monoxide test recommended)
- Burner: clean orifices; verify clean blue flame
- Igniter: HSI resistance check (typically 40 - 200 ohms cold) OR pilot inspection
- Gas valve: 24V operation; manifold pressure verification
- Flue: blockage check; combustion analyzer test recommended (CO target <100 ppm air-free)
- Inducer motor + pressure switch
Heating section (electric)
- Heat strip operation + amperage draw
- Sequencer or relays
- Limit switch operation
- Element condition (resistance check on individual elements)
Heat pump specific
- Reversing valve: solenoid energization in heat mode; valve seat
- Defrost board + control: test defrost initiation
- Outdoor coil: heat-mode operation (lower differential than cool mode)
- Auxiliary heat staging
Controls + thermostat
- Verify thermostat function (cooling + heating call)
- Fan auto + on operation
- Setpoint accuracy
- Schedule programming (commercial often has time clock + economizer)
- 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
NEVER skip the HEAT EXCHANGER inspection on gas RTUs. Cracked heat exchangers vent carbon monoxide into the supply airstream - into the customer's occupied space. Annual visual + combustion-analyzer CO test is the safety responsibility. A failed inspection that you didn't catch becomes the contractor's liability + a potential OSHA / EPA / criminal issue if someone is harmed. Document every heat exchanger inspection with photos; flag any concern in writing to the customer.
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:
Multi-RTU customers get volume discount; 5+ RTUs typically gets 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
- ACCA Standard 4 (Commercial HVAC Maintenance)
- 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