Commercial HVAC System Gas Leak, Since the fall of 2024, we’ve noticed a strong smell of natural gas coming from the hot air vents. A few days after detecting the odor, the HVAC system automatically shut down. About a year ago, after a technician replaced a new spark igniter on the burner, we noticed a slight gas smell at that time, which gradually worsened.
Between December 2024 and February 2025, we contacted technicians from several companies. Despite replacing components like the motor and air sensor, they couldn’t identify the source of the gas leak. Unfortunately, we incurred significant expenses due to travel charges and hourly rates.
Eventually, we reached out to ATCO Gas to investigate the leak. They conducted a thorough inspection at no cost. We also reviewed the HVAC package unit’s manual and examined parts related to gas leaks. Through our own research and efforts, we were able to identify and resolve the issue. We’d like to share our experience to help others facing similar problems.
Technician change parts
We informed the first technician that we began noticing a gas smell after a technician replaced the spark igniter on the burner a year ago. We emphasized that the gas odor had become significantly stronger. However, Since the system was not functioning two weeks, he recommended replacing the motor and two airflow switches. During his second visit, he replaced the air sensor. Despite these efforts, the gas smell persisted. He mentioned that he had tightened the modulator valve and suggested that the odor was not gas but rather the smell of burning foreign substances. He appeared to have done his best.
A few days later, an ATCO Gas technician visited to inspect the issue. After checking the system, he advised us to use only the cold air occasionally and to contact a technician, as the situation was hazardous. Ultimately, the first technician was unable to resolve the underlying gas leak problem. Nevertheless, they charged us over $4,000. The new parts he installed are as follows:
- Motor
- Two airflow switches
- Air sensor
1. Motor
US motors nema premium cap start general purpose – model T63CXCPR-2178.
2. Cleveland controls model: AFS-222-221-341 Two Air flow switchs
3. MAXITROL TS114 Air Sensor(55*-90*)
Online order parts change
Second Technician’s Assessment and Actions
We called a technician from another company. He suggested that the Maxitrol A1014R Amplifier appeared to be faulty and recommended replacing it with a new one. The quoted price for the new Maxitrol A1014R Amplifier and labor exceeded $800. To reduce costs, we purchased the amplifier online for $320 and installed it ourselves. However, the gas leak persisted.
1. Maxitrol A1014R Amplifier
- (Function) A1014R amplifier is a key component of the Selectra Series 14 system, which is designed to maintain precise and stable gas-fired temperatures.
- (Modulation) The system utilizes electronic Modulator or Modulator-Regulator valves to control gas flow with instantaneous response and continual adjustment.
- (Temperature Control) The amplifier supplies output voltage to the M/MR valve, which in turn controls the gas flow based on the temperature setting
Third Technician’s Assessment and Actions
We called a technician from another company. He claimed that the burner had a crack and recommended replacing it with either a used unit (price unspecified) or a new one priced at $3,000. To explore more affordable options, I searched on eBay and found that the gas pipe component of the burner was being sold separately.
Upon closer inspection, I discovered that the burner was constructed by attaching trumpet-shaped components to a gas pipe using screws on both ends, as well as on the top and bottom. The gas pipe itself was thick and robust, making it unlikely to crack. I concluded that the burner required resealing on both ends and reassembly with screws.
Fourth Technician’s Assessment and Actions
Since we were still uncertain about the root cause of the gas leak, we sought assistance from manuals and various YouTube technicians. Based on their guidance, we decided to purchase a Modulator Valve and a Straight-Through Flow Regulator online and arranged for a fourth technician to install them. Each technician visit cost us over $400. Unfortunately, even after these replacements, the gas smell persisted
2. Maxitrol RV53-34, 3/4″ NPT- Straight Through Flow Regulator
(Potential Causes of gas Leaks)
- Debris: Foreign particle like dust or dirt can lodge on the valve seat, preventing a proper seal and causing leaks.
- Worn Parts: Over time, the rubber seat poppet or other internal components can wear out, leading to leaks
- Improper Installation: incorrect installation or connections can also lead to leaks.
- Witness Mark: On service regulator, it’s normal to find a witness mark on the valve seat from the sharp orifice pushing into the soft rubber seat. Over time, this mark can get deeper or even get small pieces of dirt lodged into it, leading to higher lock-up.
3. Maxitrol M611 -34 3/4″ Modulator Valve
The fourth technician observed that the previously installed modulator valve had been connected in the reverse direction. This misconnection likely contributed to the ongoing issues with temperature control.
It’s important to note that installing a modulating gas valve in the incorrect orientation can disrupt the furnace’s ability to regulate temperature effectively. Proper installation, as outlined in manufacturer guidelines, is crucial for optimal system performance.
- For atmospheric, infrared, and direct fired burners, modulator valves provide precise, non-fluctuating, instantaneous temperature control without requiring a motor or mechanically driven butterfly valve.
- modulator valves control gas flow with instantaneous response and continual adjustment to maintain constant discharge air temperature.
- modulator valves control gas flow with instantaneous response and continual adjustment to maintain constant discharge air temperature.
- and also designed with safety in mind. they feature a variety of built-in safety features, including pressure relief vales, gas leak detection sensors, and flame arrestors, to ensure that they operate safely and reliably even in challenging environments.
NP-1 AIRFLO burner sealed with Pipe Thread Sealant
As a last resort, we decided to remove the burner, apply sealant to the trumpet-shaped connections on both sides of the gas pipes, and then reattach it. This decision was influenced by the ATCO Gas technician, who had also indicated that gas was leaking from the side of the burner.
After a few hours of work, we completed the reassembly and checked for gas odors. To our relief, the gas smell was completely gone—a moment that truly felt like a reward for our persistent efforts. The air temperature was now precisely as expected, and all the new components functioned seamlessly together.
Reflecting on the past year, we recalled that a technician had cleaned the burner and installed a new spark igniter without applying any sealant during reassembly. This oversight led to significant stress and financial costs for us.
Additionally, we have a question: Was the system’s complete shutdown due to a motor failure, or was it a temporary halt triggered by a safety device in response to the gas leak?
It’s quite possible that the system’s shutdown was a safety response to the gas leak rather than a motor failure. Modern HVAC systems are equipped with various safety mechanisms designed to prevent hazardous situations. For instance, if a gas leak is detected, the system may automatically shut down to prevent potential dangers such as fires or explosions.
I would like to share our experience with a commercial HVAC system gas leak. I believe many restaurant owners may encounter similar challenges. This issue taught us two valuable lessons:
- When a technician visits, it’s beneficial to identify the faulty component beforehand and consider purchasing the replacement part online.
- By gathering information from YouTube technicians, it’s possible to resolve certain problems without professional assistance.
Ultimately, our proactive efforts played a crucial role in addressing the issue.