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Ignition Systems – One More Time?

by George Lanthier*

This is a second update on the fifth article I ever wrote back in January of 1992 and updated again in 2000. We missed a 10-year update in 2010, so here goes.

One of the things that all of us have heard is that they don’t build ignition transformers like they used too. In the past it was not unusual to see a 30- or 40-year-old oilburner with the original ignition transformer, and now it seems they just don’t last. Is it the fault of the manufacturers or have there been changes in our servicing policy over the years?

Let’s take a look at that old gun‑type burner. First of all, the design is not that of a flame retention head. The fire may have little or no distinctive shape or patterns. Flame control was poor or totally nonexistent. Not a lot of efficiency here, Figure 1, and yet these burners were mostly run on intermittent ignition or what we now call interrupted. First generation oilburners were pretty crude by today’s standards. One of the biggest problems with these burners was keeping the flame stable, and in many cases a good cure‑all was to put the burner on intermittent (formerly constant) ignition.


Figure 1

The next design to come along was the Shellhead® and its clones. Those of you that have serviced these burners know that this burner had a flame shape (sunflower) that was quite defined and controlled and that the preferred ignition operation was interrupted. Every OEM I ever saw demanded intermittent back then (today’s interrupted) because if the flame and draft were not stable you needed to adjust them.

The motor on most of our older burners was low speed (1725 rpm). The air coming down the air tube is really not moving with a lot of velocity as it does with today’s high velocity burners. Not much chance of blowing the spark out, right? Oh, sure, but first you have to get it to light. And oh yes, finally look at this if you will, the burner is operated by a stack-mounted protector relay, what most of us call a stack switch, Figure 2. Now before you think that I’m crazy in bringing this all up remember that this is not high tech, this is low tech, but it works. Many of the old timers will say the damned guy is right AND I am off my rocker!


Figure 2

Finally, I bring to you the high‑speed, high velocity flame retention head burner. A few years ago constant ignition became a gas pilot, intermittent ignition became constant ignition on power burners and interrupted ignition was born, or maybe just picks up a new name. Are you confused yet? Read on.

Man has gone to the moon, he can go across the Atlantic in three hours and we can microwave a hot dog in a minute but we cannot get a transformer, Figure 3, or


Figure 3

electronic ignitor, Figure 4, to last more than two or three years. What in the blazes is going on here?

Figure 4

Figure 4

How would you feel if you had just purchased a new burner two years ago and six months into the deal the serviceman had to come and reset the electrodes? At the annual cleaning, he had to adjust them again. And now, two years and five ignition adjustments later, the transformer has to be replaced. This is reliable, safe and efficient oil heat? Well, as it turns out it’s not all the transformer’s fault, and all is not lost. You may not believe this, but the problem is probably the primary control you are using that’s killing all these transformers. Remember that reference to the stack switch? That’s the key to the puzzle.

While working as a burner rep a few years ago I was responsible for coming up with ways to teach the product which were technically correct, but would show the advantages of that burner over the others on the market.

It was at that time that I found that I might have stumbled across a secret formula. Back in 1990 I worked on a new text for the industry (The Petroleum Marketing Education Foundation’s Oil Heat Technician’s Manual, 1990 Edition) which also includes this secret formula. Let me give away “the secret” that’s now been carried over to the current NORA Oilheat Technician’s Manual and is one of the keys to keeping today’s burners, even with today’s fuels, running right.

Let’s say that we have a residential oilburner, which consumes 1,000 gallons of oil per year through a 1.00 gph nozzle. Further, to produce both heat and hot water, the burner will start about 2,300 times per year. Therefore, with this criteria established let’s look at what would happen.


Intermittent (constant) ignition = ignition is on when burner runs

1,000 gallons at 1 gph = 1,000 hours of ignition on time.




Interrupted ignition = timed or sequenced ignition.

  1. Stack type relays (typical)

2,300 starts x 60 seconds = 38.3 hours ignition on time.

  1. Cad‑cell type relays

2,300 starts x 45 seconds = 28.75 hours ignition on time,

2,300 starts x 30 seconds = 19.1 hours ignition on time,

2,300 starts x 15 seconds = 9.5 hours ignition on time, and

2,300 starts x 8/10 seconds = 30.5 minutes ignition on time.


That’s right! The stack switch only runs the ignition system for 3.8% of the time that the infamous three‑wire cad‑cell control does. But take a closer look at that 8/10-second unit; it only operates the transformer 0.0005% of the time. Or, put another way, that transformer which previously had a life expectancy of just one year now has a life expectancy of 2,000 years.

As you can see, by changing the control type, you probably won’t have to change as many transformers. You also will lower the number of service calls for electrode adjustments between tune‑ups, and will probably have a happy customer who has no reason to switch to another fuel. Remember that burner company I mentioned working for, well their burners have ignition on for only 8/10 of a second during normal light off so they have a good reputation for not only lighting off smoothly, but also for very few ignition problems. But as I have shown you they just know ‘the secret.’

Three more things that you may also want to consider:

  1. Most commercial/industrial burners are run on interrupted ignition which generally, after proving flame on low or pilot fire, shuts off in less than one second.
  2. No burner manufacturer that I have spoken with has ever recommended constant ignition on flame retention designs except for just a couple of unusual problems. As always, the manufacturer should be consulted first should you feel that you have an unusual job.
  3. If you can’t get a burner to light and run on interrupted ignition you have a draft (air-flow) problem, FACT!

So the original question here was–did they build transformers better in the old days? I don’t think so, but who knows? I guess the burner men who do know are the ones who run their burners with interrupted and not intermittent (constant) ignition.

Okay, so we’re back to 2016. Amazing isn’t it? At the time that this article was originally published 24 years has passed and a few things have changed. The PMEF book became the PMAA book which became the NORA OTM. In 1992 there were only two primary control manufacturers making controls available that would provide interrupted ignition, now there are five: Beckett, Carlin, Honeywell, ICM and Riello. Stack switches were made illegal in Massachusetts on new installations in 1995, and in 2014 Massachusetts banned anything other than 15 second safety, interrupted ignition controls. I’m still off my rocker making predictions, but some things never change. At this point, if you’re still wondering why people who use interrupted ignition are having fewer problems than you are maybe now you know why.

See ya!

*George Lanthier is the owner of Firedragon Academy, a Massachusetts Certified School teaching both gas and oil. Firedragon Academy now has multiple facilities in Massachusetts and New England for teaching both their gas and oil “hands-on” schools and seminars. Firedragon is also a publishing firm publishing George’s over 60 books and manuals on gas and oil heating and HVAC subjects. He is a CETP, NATE, NORA, PMAA and PMEF Proctor and has been a Massachusetts Certified Instructor since 1975. He can be reached at 608 Moose Hill Road, Leicester, MA 01524. His phone is 508-421-3490 and his website can be found at FiredragonEnt.com

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