Troubleshooting HVAC Systems: It’s All About How You Approach the Job Site
I’m sort of a health nut. You may know the type: organic lean protein shake, fresh fruits and veggies, loads of exercise …
While on a run the other day, I recalled the words of hydronic ace/sensei John Barba, residential training pro at Taco Comfort Solutions.
“The troubleshooting mind is like a parachute,” he said. “Both must be open to work properly.”
Troubleshooting a boiler is pretty simple if you remember that boilers, like bodies, do well with good fuel or food and seasonal maintenance — like smart diagnostics or exercise, if you will.
Troubleshooting Tip No. 1: Don’t assume you know what the problem is before you get started.
Troubleshooting Tip No. 2: Always perform troubleshooting analyses systematically.
Barba has a friend, Jeff Young, who’s known as “Heatboy.” Young is a longtime radiant heat and boiler expert. He once told Barba the story of a finicky propane boiler. Apparently, Young was the fourth technician to attempt to figure out why a certain boiler was having issues.
“There were five or six gas valves on the floor,” said Young. “The other guys figured they were all bad and kept replacing them. I’m no genius, but the odds of five or six brand new gas valves being dead on arrival are pretty slim.”
The problem, explained Young, was that the boiler would work fine much of the time. However, most mornings and evenings, it would lock out on low gas pressure. It would lock out unpredictably at other times, too, but early morning and early evening were most common.
Every other service guy figured the problem had to be those “piece-of-junk” gas valves, especially since the homeowner kept telling each new guy the gas valve had crapped out again. So, they simply kept swapping them out.
Someone needed to open the parachute of their mind. Young started by applying Troubleshooting Tip No 1: Don’t assume you know what the problem is.
Logic was on his side, too. You simply don’t get six straight “bad” gas valves — unless, of course, there was a national recall out on them.
So how did Heatboy nail down the problem? By applying Tip No. 2: Systematic troubleshooting. A problem is solved in a logical, orderly manner. You know, a system.
First, identify the sequence of operation from the very beginning. Young had two operation sequences to follow: the call-for-heat sequence and the get-propane-to-the-burner sequence. By applying some logic, he decided to eliminate the call-for-heat sequence by running it through its paces. He turned on the thermostat and followed the wires.
- T-stat to relay? Check.
- Hot side of the relay to zone circulator? Check.
- Dry side of the relay to the boiler control? Check.
- Boiler control to burner control? Check.
- Burner control to spark ignition? Check.
- Burner control to gas valve? Check.
- Nice blue flame? Check.
In a matter of minutes, Young eliminated 50 percent of the possibilities and narrowed his detective work to the get-propane-to-the-burner sequence.
He started with the ridiculous by checking the propane level at the tank. Sounds silly, but it checked out. He then made sure there were no leaks between the tank and the boiler (and other appliances).
Next, he pulled out his manometer and checked the gas pressure at the boiler to make sure the gas pipe was sized properly. There was plenty of pressure, so that was eliminated.
Plenty of propane, no leaks, and adequate pressure. Young had already done more than any of the previous service techs and still hadn’t found the problem. He then applied the next tip.
Troubleshooting Tip No. 3: Think about the problem, and ask yourself some questions.
The boiler would typically lock out in the morning and the evening as well as at other arbitrary times. Why would a boiler behave that way? What would cause the gas pressure to drop at the boiler at certain times of the day? He thought about the fact that the boiler was at the very end of the gas line: There was a water heater, a dryer, and an oven between the boiler and the propane tank.
What if the water heater was running at the same time? That would happen in the morning when folks are showering, wouldn’t it?
Young fired the boiler and then turned on the hot water. By simply watching the boiler flame, he could see it dim considerably when the water heater burner switched on. Still no lockout, but by golly, a clue!
People sometimes cook in the morning, don’t they? So, he activated some of the stove’s burners, then watched the boiler flame dim even more.
Do people run the dryer in the morning? Sometimes, I suppose. Let’s see what happens. He turned on the dryer, and off went the boiler.
It was the perfect storm — a call for heat combined with showers, breakfast, and wet clothes. He asked the homeowner about family routines and found that the teens do their own laundry and usually wash them at night and dry them in the morning before school. At the same time, everyone’s showering and making a hot breakfast. The result? The boiler control locks out due to low gas pressure.
That explained why, but it didn’t solve the problem. Shouldn’t the system be sized to handle the whole shooting match? And again, Tip No. 3 applies — ask yourself another question.
There was plenty of gas in the tank, the pipe was sized properly, and there were no leaks. But as more appliances fired up, the gas pressure fell like a lead weight. What could cause that?
The only other item in the chain that hadn’t been specifically checked was the regulator at the gas tank. As it turned out, the propane company put the wrong regulator on the tank way back when the job was first installed.
Looking back, the answer was pretty obvious, but it had evaded several different techs. I mean, who would guess the propane company itself had installed the wrong regulator?
What Heatboy did was eliminate the guesswork by applying systematic troubleshooting and asking questions. Once you eliminate all possibilities, whatever’s left — no matter how farfetched — is usually the culprit. Mysteries are like that.
Publication date: 5/14/2018