for a new boiler, and it works best when the burner is off, and now they send another guy!”
“ When the burner is off”, questions Bubba,“ please explain what you mean.”
“ Wow, now there’ s the first change”, says Mrs. Nastybear,“ he just doesn’ t want to go down the basement, okay here is what happens. We have a clock thermostat because we both work, we like it cool at night, and we’ re still trying to save money( some things never change). After the heater has been off for a while and it first warms up, it heats fast, and the radiators start to get hot.
Then the radiators don’ t get any warmer, and the burner keeps running. Then the burner shuts off, and then just when the radiators start to warm up again, the burner comes on and the radiators don’ t get any hotter. Just like I said, it’ s better with the burner off”.“ I think I know what to do”, says Bubba,“ let me have a look at it.”
After being in the basement for some time, Bubba comes up and announces to Mrs. Nastybear that he has replaced a control, made some adjustments, and now feels the problem is fixed. Do you know what control Bubba changed, and what adjustments he made? And why did the radiators act this peculiar way? Well, here’ s the story he told Bruce, so let’ s see what happened.
“ I arrived at the job Uncle Bruce, listened to the customer tell her story and replaced the new existing pressure control, Figure 1. It was running way over three pounds before it shut off, and I couldn’ t get it to run the burner the way you showed me. I put on a vapor type control, Figure 2, and set it to shut off( cut-out) the burner at 16 ounces and to cut the burner back in( cutin) at four ounces. The radiators got nice and hot, and the customer seemed happy”, explained Bubba.
“ Well, I’ m glad you remembered what I told you about pressures, and did all of the air vents work”, asked Bruce.
“ Boy, I think so,” replied Bubba,“ because you told me that at 1-1 / 2 psi those vents, Figure 3, are supposed to close, and all of them did, they wouldn’ t let any more air out, and so no more steam came in, just like she said,‘ it worked better when the burner was off”. But my question is why does the vapor control work so much better?”
Figure 2
Figure 3
“ It has to do with pressure and in this case, size does matter”, replies Bruce.“ See that small round thing just above the brass fitting, Figure 1? That’ s where the diaphragm that operates the control is. Internally it’ s about the size of a silver dollar. Now on the vapor control it’ s about the size of a cup saucer, big difference and why the vapor control just works better because it reacts to the steam vapor better. I guess I better call Friendly’ s and tell them the news, and then bill them for the call and the control”, said Bruce.“ They will have a fit over the price of that vapor control, but if they had
Figure 1 put one on with the boiler, they could have saved themselves eight service calls, oh well.”
Figure 4
Did you figure this one out for yourself?
Remember these important facts:
1) The # 1 air vent, Figure 4, or its equivalent, Figure 3, were designed to run at a maximum of 1-1 / 2 psi, and if you go over that they do their job and shut down. It’ s called drop away pressure, Figure 5.
2) Normal pressure controls have minimum operating ranges of. 5 psi to 1.5 psi and may not be sensitive enough to work with many systems with new faster steaming boilers.
Figure 5
3) Vapor controls run on ounces, and the correct one for residential should have a maximum operating pressure of 1 psi( 16 ounces).
4) Most, if not all, residential steam systems ever designed were laid out for an operating maximum pressure of two psi. 5) Any control, regardless of price, is cheaper than repeat calls. This is a common problem, and so I have to keep wondering when everybody will put on the right control to begin with? Don’ t think that all you have to do is up the capacity of the air vents either. If you do, you will create even bigger problems. What problems you ask, well, how about problems with‘ water hammer’, condensate return, and if an automatic feeder is present, flooding of the boiler. Take the easy way out, put on a vapor control. l FON
George Lanthier is the owner of Firedragon Academy( www. FiredragonEnt. com), a 35-year-old Massachusetts Certified School teaching gas, oil and other heating subjects. The Academy has its training facility in Webster, Massachusetts. Lanthier is the author of more than 60 books and manuals on HVAC subjects, published by Firedragon. Lanthier is a CETP, ESCO, NATE, NORA, PMAA and PMEF Proctor and has been a Massachusetts Certified Instructor since 1975. www. fueloilnews. com | FUEL OIL NEWS | JANUARY 2026 27