Steve Miles, inventor

Cracked heat exchangers give a whole new meaning to the phrase, “crack kills.” Steve Miles, general manager of Jerry Kelly Heating & Air Conditioning, St. Louis, has other interesting phrases that promote his newly invented Visible Defects (VD) Visual Detection System. Better known as Crack Finder, No Cracks Allowed, and Eliminate VD, Practice Safe Heating, are his company’s mantras.


Packaged in bright, lime green boxes, the visual detection kit contains a padded carrying case, a 12-inch injection sprayer, a black light UV LED flashlight, instructions, sprayer with flexible hose, a 22-inch, 90-degree spray bar, yellow UV blocking safety glasses, a break resistant inspection mirror, 1 gallon of dye, and 10 handouts for customers, explaining why heat exchangers fail.

According to Miles, between 30-50 percent of heat exchangers older than 10 years are cracked. Heat exchangers, however, are expensive and can be difficult to inspect. Besides the diagnostic difficulty, customers are often a hard sell.

“A furnace with a cracked heat exchanger can still be working, and usually is, which means the gas will be circulated throughout the house - silently - and over a period of time,” said House Master, a national home inspection firm. This still working, expensive, but deadly piece of machinery now needs to be replaced and the customer just isn’t buying it.

“We needed a way to find cracked heat exchangers,” said Miles. “We needed a way to show that crack to the customer.”


Miles started working on the Crack Finder project four years ago. He found that no matter how he approached the subject, it was physically difficult to show a customer that there was a problem. As a pilot, Miles had seen dye penetrant inspections used in multiple aviation and industrial applications. Combining his HVAC and aviation skills, he began to experiment with different formulas.

“The biggest obstacles were finding something that worked well, was easy to apply, didn’t put off noxious odors, and was safe to use,” said Miles. “It took me about two years of trial and error before finding the current formula.”

First and foremost, it had to be visible. Contractors can’t fix what they can’t see, and it is hard to convince customers of an invisible crack. “I tried a little bit of everything,” remembered Miles. “Anything that glowed fluorescent, I tried.”

Finding a substance that could be seen and would penetrate wasn’t nearly as difficult as finding a substance that didn’t leave behind a noxious odor. After one experiment, the entire house smelled like smoke and it was back to the drawing board.

Miles didn’t let his idea go. He finally came up with a water-and alcohol-based formula that is nontoxic, low-odor, and gives off no smoke. “The alcohol breaks the surface tension, and penetrates throughout the exchanger,” explained Miles. “The alcohol was added to the water to make it seep through, and water was added to the alcohol so it wouldn’t catch fire. The dye was added so it could be seen.”


Once a visible solution was found, procedures were created. Contractors must first run the blower for 5-15 minutes to cool off the heat exchanger. When finished with that, the formula should be applied and allowed to set for 30 seconds.

The formula can be applied to the entire heat exchanger through holes in the front panel as small as 1/8 inch on 60-80 percent furnaces and some 90-plus sealed combustion furnaces, or it can be injected into the cells on tubular-style heat exchangers, according to Miles. Whether or not the dye is applied to the air side or combustion side depends on the type of furnace. For most standard and 90-plus furnaces, the dye is applied on the air side of the heat exchanger. It can then be inspected through the burner compartment.

On tubular heat exchangers, the formula is injected into the tubes at the combustion chamber by the burners and inspected from the air side through the plenum, the insertion limit hole, or the blower compartment.

Once injected and visibly inspected, it is imperative to video document the crack, according to Miles. “Failure to leave video documentation with 100 percent of the customers whose heat exchangers you can condemn can result in your company’s reputation being destroyed,” warned Miles. “Remember, it’s just another tool in the toolbox, and should be used with all of the other tools at your disposal for a thorough diagnosis.”


Skepticism is not the only problem contractors will face. Utility companies and home inspectors add interesting perspectives to the safe heating mix.

“Local gas companies don’t want anything to do with it,” said Miles. Most utility workers are not properly trained to identify cracked heat exchangers. Miles remembered showing his invention to a local gas employee one day, asking him, “How many of these do you think you have missed?” The employee replied, “I don’t want to talk about it.”

Combined with the video, the Crack Finder kit helps boost contractor credibility, said Miles. When contractors condemn a furnace and the gas company comes out two days later and says the furnace is fine, customers begin to question contractors’ motives. Miles said his invention helps give the technician credibility while taking away customer doubt.

“We don’t claim it will find every defect in a heat exchanger, but you will find more with it than most will find without it. It’s just another very effective tool to have in your arsenal.”

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Publication date:12/11/2006