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Questions regarding the main vent and auto water feeder that cuts off the boiler every 10 minutes
Just finished reading We Got Steam Heat. Wow, it’s a great read. I also bought The Lost Art of Steam Heating, which will take more time to study. I’ve begun to explore my single-pipe steam heating system and thus far have come across two questions: (1) where is the second main vent (if any)? (2) what’s up with the auto water feeder cutting off the boiler every 10 minutes.
To back up, I bought the home 15 years ago and right away converted from oil to gas. The system worked well enough. I figured out how to reduce knocking by tilting the radiators. The system does heat up slowly and some rooms are always colder than others. I thought that was normal, until I came across this website and read the book.
Question 1: the main vents. My system has two mains: The insulated main is 18 ft. and feeds 5 risers; the other main is 33 ft., uninsulated but is wrapped in a chute with grating on the side that allows some heat to warm up the basement. This uninsulated main also has 5 risers. I have 13 radiators (6 on the first floor and 7 on the second and I’m not quite sure how the risers match up with the radiators). I could not find any main vents in my initial survey of the piping. A fairly knowledgeable plumber said they should be at the ends of the main, but he also could not find them. I was beginning to believe the system must not have them. Then I remembered that seller of the house was the estate of an old plumber. The plumber might have been one of the Deadmen himself. How he could he not install main vents? Then I found a main vent covered with dust inside the end of the chute, after the last riser and right before the main turns into the return. But why did he seal the main vent into chute, which is difficult to take apart? After more careful examination, I noticed several screws on the side of the chute and voila, a small cover comes off and allows easy access to the Dole 4A main vent. After at least 15 years, probably 20 years, this vent still appears to work. It’s very quiet but I can feel hot air coming out of it at the beginning of a heating cycle. I have had no luck finding a vent for the insulated main. Attached are pictures of the ends of both mains. Could it be that the second, uninsulated main lacks a vent and that the air is vented through the radiators upstairs?
Question 2: Is it desirable for the auto water feeder to shut off the boiler every 10 minutes? The oil to gas conversion did not include an auto water feeder for the Peerless gas boiler (61-05-STDG-S). I got tired of checking and adding water myself and had an auto water feeder (an ITT McDonnell Uni-Match Universal Waterfeeder) installed separately. A label next to the on-off switch of the boiler says the following:
“Water level proving relay. The relay in this box will turn the boiler off every ten minutes during the heating cycle to allow the water level probe control to verify the water level.”
And sure enough, during the firing cycle, the boiler will abruptly shut off and restart a few minutes later. One plumber says this is inefficient. Another says he’s never seen such a 10 minute cut-off device. A third told me not to worry about it. It seems to be inefficient for the boiler to cut off mid-steam for the water level check. Is there a way to change the interval from 10 to say 20 minutes?