Packaged rooftop units (RTUs) heat a large share of the commercial buildings in Southeast Wisconsin – retail centers, offices, schools, light manufacturing, and warehouses. They are built for outdoor duty, but heavy snow, drifting, and ice create problems that can shut a unit down or create unsafe operating conditions.
At BREDAN Mechanical Systems, our service technicians spend a lot of winter time on snow-covered roofs. Here is what we see most often, and how facility teams can reduce the risk.
Why Snow Is a Problem for Rooftop Units
Blocked Flue Outlets
Gas-fired RTUs vent combustion products through a flue outlet on the side of the unit. When snow drifts against the unit, that outlet can become blocked. The result is a pressure switch lockout at best – or poor venting at worst.
Starved Combustion Air
Burners need a steady supply of combustion air. Snow and ice packed into the combustion air intake cause ignition failures, flame rollout, and repeated lockouts.
Outdoor Air Intakes and Economizers
Snow pulled into outdoor air hoods can wet filters, freeze dampers in position, and trip freeze stats. An economizer frozen open can bring sub-zero air directly into the building.
Condensate and Drainage
Condensate lines and roof drains near units can freeze, leading to water backing up into the unit or ponding on the roof.
After Every Significant Snowfall
- Clear snow away from flue outlets and combustion air intakes
- Check outdoor air hoods and filter sections for packed snow
- Confirm units are running and not in lockout
- Look for ice buildup on fan guards and condenser sections
- Keep a clear path to each unit for service access
Only trained staff using proper fall protection should work on roofs in winter conditions. When in doubt, call your service contractor.
Long-Term Protection Measures
Raise the Equipment
Units mounted on low curbs in drift-prone locations are blocked repeatedly. Taller curbs or relocating intakes can solve the problem permanently.
Flue and Intake Extensions
Manufacturer-approved vent extensions and snow hoods keep critical openings above typical snow levels.
Heat Trace on Condensate Lines
Heat trace and insulated condensate piping help prevent freeze-ups that cause water damage.
Alarm Monitoring
Connecting RTU lockout alarms to your building automation system means you learn about a failure in minutes, not when occupants start calling about cold spaces.
Heavy Snow Loads
Deep snow and ice add significant weight to roofs and rooftop equipment curbs. Watch for sagging, roof leaks around curbs, and doors that stick on the floor below – all potential signs of excessive load. Snow removal should be planned so equipment, gas piping, and roof membranes are not damaged.
Rooftop Unit Service in Southeast Wisconsin
BREDAN Mechanical Systems services commercial rooftop units of all major brands throughout Waukesha, Milwaukee, Kenosha, Racine, Washington, Ozaukee, and Jefferson counties. From winter emergency calls to vent extensions and BAS alarm integration, our team keeps your rooftop equipment running all season. Contact us to schedule a winter rooftop inspection.
