RTU Stopped Working at
Korean BBQ Restaurant
Complete rooftop unit failure during business hours. VFD burned out, belt worn through. Full HVAC restored same day — restaurant stayed open for dinner service.
RTU on rooftop · San Jose
Belt drive + CO2 sensor
ABB VFD replacement
The Problem
RTU Completely Down
Restaurant called mid-morning — rooftop packaged unit had stopped working entirely. No cooling, no airflow. Dining room temperature rising toward 80°F with a full lunch service ahead.
- No airflow from supply vents
- Unit making no sound at all
- Dining area approaching 80°F
- Full restaurant expected for lunch
Our Diagnosis
VFD Failure + Belt Worn
Rooftop inspection revealed two issues: the ABB variable frequency drive had failed with a fault code on display, and the blower belt was cracked and near its breaking point.
- ABB VFD showing fault code — no motor output
- Drive belt cracked and slipping
- R-410A pressures normal — refrigeration side OK
- Telaire CO2 sensor functional — not the cause
What We Did
VFD + Belt Replaced
Sourced replacement ABB VFD locally. Installed new drive, wired and programmed to match motor specs. Replaced worn Fenner belt. Full system test before leaving the roof.
- Replaced ABB variable frequency drive
- Installed new Fenner Drives belt
- Verified motor operation at all speeds
- Confirmed airflow and cooling restored
- Restaurant open for dinner service
Project Photos
On-Site Documentation
RTU exterior · before service
Blower compartment opened
ABB VFD — replaced
Belt drive + Telaire sensor
RTU with North Breeze cap
Restaurant Stayed Open
VFD replaced, belt replaced, system fully operational before evening service. Manager confirmed full cooling restored — dining room back to 72°F with no business interruption.
80°
→ 72°F
2
Parts
0
Downtime
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