The loneliest place in the world for a service technician is standing in front of a dead boiler on a bitter Friday night. “What do you think is wrong?” the apartment building owner asks. Fighting the urge to say, “I just got here,” you shrug your shoulders. You’ve never serviced this boiler and believe no one has in a while. The snow that fell from your boots isn’t melting, and your breath is creating vapor. The stakes of not getting the boiler started run through your mind: frozen pipes, burst coils, upset owner and angry tenants ready to leave. Where can you find portable heaters at 9 p.m.?

The pressure you feel is from knowing the building depends on you. Nobody else in the building understands combustion air, venting or flame sensors.

For all they know, a hamster on a wheel is generating heat. To them, it’s just a big gray box that heats their building. To you, it’s a living, breathing system with its own distinct personality, but not tonight. Compounding the stress, you realize there are no parts counters open, no manufacturers reps to ask, and no coworker there to bounce ideas off. You are flying solo. Taking a deep breath to steady your nerves, you get to work.

Cold call reality

The first thing I do when walking into a boiler room is to look for an escape route and mentally commit it to memory in case something happens. A runaway boiler or water heater could fill the room with steam in minutes. If it does, steam displaces air, so breathing is labored. Secondly, in a room filled with steam, visibility drops to zero, making you blind. 

In these high-stakes moments, the best technicians don’t panic; they slow down. A boiler doesn’t fail randomly; it leaves clues, and your job is to use your senses to uncover them. Do you smell something burning? Is there an unusual vibration? Is it off on a tripped control? Boilers speak, if you listen.

The hardest skill to teach isn’t wiring diagrams or flame signals, it’s patience. In a world of instant answers, it’s tempting to hit the reset button and hope for the best, but a boiler isn’t a smartphone app. Resetting erases evidence of why it failed, and it will fail again. In these cases, it’s best to go back to the basics: Air enters. Fuel mixes. Spark ignites. Flame burns.

Looking for clues

Is there a call for heat? Using a multimeter, you confirm the call for heat at the burner, meaning the boiler safety controls are satisfied. The next step is pre-purge. During pre-purge, the blower runs for 30 seconds to 2 minutes to eliminate any unburnt fuel from the boiler and chimney. The length of the pre-purge time is based on how long it takes for four complete air changes in the combustion chamber. So far, so good.  

The next stage in the sequence is the pilot. The pilot solenoid valve opens, and the electrodes spark, igniting the pilot. You can verify the pilot is lit by reading the flame signal and carefully looking inside the sight glass. I usually do both. 

After the pilot is lit and verified, listen for the gas valve opening. I typically use a contactless voltage tester to verify power is present and place my hand on the valve to feel movement inside. There is power to the gas valve, and I felt it operating, but there is no flame. The valve has to be defective, right? We have power and gas to the valve, but no flame. 

You mentally inventory the stock on the shelves in the truck. Do I have a replacement gas valve? Not one this big. Then you see it, quarter-inch tubing connected to the valve. A story an old timer told you about a vent tube clogged with a spider web comes to mind. It can’t be that you think. After unscrewing the brass nut holding the tubing on the valve, you lift the tubing from the valve and press the reset button. The time it takes for the preignition steps feels like an hour. Suddenly, a flame appears in the sight glass. 

“Is it on?” the owner asked, and you nod. Inside, you are leaping up and down with your fists in the air. Now comes the real test: shut off the boiler and restart it, fingers crossed. Whoosh. After blowing out the vent tube and evicting the spider, the tube is reconnected to the gas valve. One more cycle. When it starts, you nod at the boiler, a sign of respect.

Patience

What separates an average technician from a great one isn’t how fast they swap a part; it’s how well they think under pressure. When you hear the soft whoosh of ignition and see the temperature or pressure gauge climb, the tension melts away. You’ve kept a hospital running, a family warm or a business operational.

This work isn’t glamorous. No one takes selfies in a boiler room, but it’s noble. We’re the unsung heroes who keep the world from freezing.

The career of a boiler technician is scary, challenging and extremely rewarding. The feeling you get when the boiler starts because of your expertise, after two other companies tried and failed, is incredible. The industry is also humbling. Just when you think you know all there is to know, a new problem arises to challenge your expertise. This industry teaches you something every day if you are open to learning. 

Welcome to Boiler Room Detective

Hello, PHC News readers! I’m Ray Wohlfarth and thrilled to launch this column diving into the fascinating world of boilers and heating systems. With more than 40 years in the industry, 14 books on boilers and my YouTube channel, Boiler Room Detective, I’ve tackled everything from cranky steam systems in historic buildings to high-efficiency hydronic setups in modern facilities.

This column will explore troubleshooting, debunk myths, share safety essentials, and highlight innovations to save you time, energy and headaches on residential and commercial steam and hydronic systems.

Whether you’re a technician chasing a fault on a residential boiler, an engineer optimizing performance, or a facility manager planning maintenance, I’m here to help you crack the case. Grab your flashlight or infrared thermometer, and let’s investigate. Got a boiler room mystery? Send it my way, and we’ll solve it together in future columns.