It's a cold morning, the building isn't warming up, and the thermostat says the heat is on. In Colorado Springs, that's not a small problem. The National Weather Service's 1991–2020 normals put the average January low around 18°F, and the city's normal year has nearly 5,900 heating degree days. Commercial buildings here lean on their rooftop units' heat sections for a big part of the year.
Here's a plain-language guide to why rooftop units stop heating, what's safe to check yourself, and when to pick up the phone.
First: safety
- If you smell gas, don't troubleshoot. Get people out of the building, avoid switches or anything that could spark, and call your gas utility's emergency line or 911 from outside.
- Don't go on the roof without proper fall protection. Rooftop work is a fall hazard, and RTUs contain high-voltage electrical parts and gas burners. Leave the roof to trained technicians.
- Carbon monoxide alarms going off? Treat it as an emergency: get out and call 911.
What you can safely check from inside
- Thermostat or controls. Is it set to heat, is the setpoint above room temperature, and does it have power (dead batteries are a classic)? On programmable or networked controls, check the schedule. Unit "failures" sometimes turn out to be an occupied/unoccupied schedule that changed.
- Breakers. Check whether the breaker for the rooftop unit has tripped. If it trips again after you reset it once, stop and call. Something is drawing too much current.
- Filters (if accessible and part of your routine). A badly clogged filter can cause the heat section to overheat and shut itself off on its safety limit.
- Is air moving at all? No airflow at the vents points toward the blower side; air moving but cold points toward the heat section or controls.
If none of that fixes it, the problem is almost certainly on the roof.
Common causes on the roof
Ignition problems. Modern gas RTUs use an igniter and a flame sensor. A cracked igniter won't light the burners, and a dirty or failing flame sensor can light them and then shut them off seconds later because it doesn't "see" the flame. Repeated attempts followed by a lockout is a common pattern.
Gas valve or gas supply. A failed gas valve, a closed manual valve, or a supply issue will keep the burners from lighting even when everything else is working.
Inducer motor and pressure switch. Before the burners light, a small inducer fan clears the combustion path, and a pressure switch confirms it's working. If the inducer is failing or the switch or its tubing has a problem, the control board won't allow ignition.
Overheating and limit trips. If air isn't moving across the heat exchanger fast enough because of a dirty filter, a slipping or broken blower belt, or a failing blower motor, the high-limit switch shuts the burners off to protect the equipment. The unit may cycle on and off without ever warming the building.
Economizer problems. Many rooftop units have an economizer that brings in outside air when it's cool enough to "free cool." If the damper sticks open or its controls fail, the unit can pull in cold outside air all winter, and the building feels like the heat isn't working even when the burners are firing.
Electrical and control board faults. Failed transformers, relays, contactors, wiring damage, or a bad control board can stop the heating sequence anywhere along the way. Colorado's intense sun and temperature swings are hard on outdoor wiring and connections over time.
Altitude setup. The National Fuel Gas Code calls for gas appliance input to be reduced above 2,000 feet unless the manufacturer's instructions specify otherwise. Colorado Springs is around 6,000 feet, and places like Monument and Woodland Park are higher. A unit that was never set up correctly for its elevation can have combustion problems or nuisance lockouts.
Heat exchanger issues. Cracks or failures in the heat exchanger are a safety concern because of the risk of combustion gases mixing with supply air. They're one of the reasons an annual heat-section inspection on gas units matters, and one of the situations where replacement is often the safer choice for an older unit.
When to call a technician
Call when:
- the thermostat and breaker check out and there's still no heat,
- the unit lights and then shuts off, or cycles repeatedly,
- you hear new banging, grinding, or rattling from the roof,
- you notice burning smells, scorch marks, or water leaking through the ceiling under the unit, or
- the building is getting cold and you have people or temperature-sensitive inventory inside.
We're available 24 hours a day, 7 days a week at 719-521-3755. See our 24/7 commercial rooftop unit repair page for the repairs we handle.
Preventing the no-heat call
Most no-heat calls trace back to parts that wear out predictably: igniters, flame sensors, belts, filters, and electrical connections. A fall maintenance visit before the heating season (inspection, cleaning, filter change, electrical testing, and a burner and heat exchanger check on gas units) catches a lot of them before the first cold snap. Our RTU maintenance agreements are tailored to your building. Ask for a quote.
If your unit is older and the no-heat calls are becoming a habit, it may be time to compare repair and replacement. Start with our free RTU assessment, and if replacement is the answer, commercial HVAC financing through Optimus is available to qualifying businesses. See financing options.
We serve Colorado Springs and nearby communities including Falcon & Peyton and Castle Rock.
Sources
- National Weather Service, Colorado Springs normals and extremes (1991–2020) and Colorado Springs annual climate summary
- National Fuel Gas Code (NFPA 54) high-altitude input rule, via UpCodes
- I.C.E. Heating & Cooling, Commercial Rooftop HVAC Repair and Replacement in Colorado Springs (common RTU warning signs and repair services)