Radiator Air Vent question

Steamhead

might be hygroscopic air vents. These are supposed to work on steam but my experience has been the same as yours.

A thermostatic vent like the Hoffman #40 will work much better. But before you buy a whole set of radiator vents, check to see if the vents on the ends of the steam mains are properly sized. Missing or too-small main vents will make the system heat slowly and unevenly. Correcting this problem, if it exists, might make next winter's fuel consumption the lowest in your 20 years at that house! Measure the length and diameter of each steam main and tell us what vent is on it.

Once your main vents are right, you can vent each radiator according to its size. Then all rooms will heat up evenly.

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Gnigamica_2

Rad Air Vent necessary?

Hello

I've been living in a house with single pipe steam heat for 20 years (Burnham Holiday boiler) without really understanding it, other than that it works. After reading through the Heating Help site, I realized that the rads are supposed to have vents that close in contact with steam. The only thing on my rads is a plug. The plug has a screw so that you can close it if you like, but otherwise it hisses and sputters and blows steam when the heat is on. I thought that was normal.

I have a local supplier who can provide vents (Hoffman Specialty Model 40). Should I replace the plugs with the vents? Or are the plugs/screws acceptable?

As I said, the system has been running for 20 years while I've owned the house, and many years before that presumably. I add water to the boiler once a week during heating season and blow off the low-water-cuttoff every couple of weeks, but it would certainly be nice not to have steam venting into the house.

Gnigamica

Main Vents

There are no vents on the mains as far as I can tell. The pipes pass across the basement ceiling from the boiler, then turn up into the ceiling and onward to the rads. I understand the main vents are supposed to be about 15 inches back from the point that the pipes turn up?

To be honest, I don't even know who I could call around here (Winnipeg, Canada), to service this system.

Steamhead

You may have a counterflow system

do the mains slope upward from the boiler location, or downward?

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Gnigamica

Main Vent

The main pipe from the boiler actually slopes DOWN by a total of about 2 inches on its trip to the far side of the basement, then turns around and comes back to the boiler dropping ANOTHER couple of inches. Pipes lead up to the ceiling from both sides of this looped pipe. I guess the slope is to ensure that any water that condenses will always flow back to the boiler. I never noticed that before.

Steamhead

That's correct

so you have a parallel-flow up-feed system. Tha main vent should be near the end of the returning portion of the pipe, after the takeoff for the last radiator. How long is this pipe, and what diameter?

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Gnigamica

The pipes measure

approximately 2.5 inches diameter, outside measurement. The length of the main pipes is... approx 19 feet on the way out from boiler, an an 18.5 foot return.

There is no vent before or after the last rad pipe. However, there is capped pipe. I've attached a photo for your consideration. And many thanks for patient pushes for the correct information.

Steamhead

It looks like

you have two steam pipes there, dropping into a tee and then into the return. Does the steam go out thru two main pipes in different directions as it leaves the boiler, with the pipes connecting together at the other ends?

You could put a vent on that capped pipe, but we'd need to ascertain the above first.

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Gnigamica

Single pipe feeds both main pipes

A single pipe emerges from the boiler piping. It's the brown pipe on the right in the picture above. It then splits between the upper main and the lower main... these two are really one pipe that loops back.



I ran the boiler and tracked the heat progress along the pipes. The steam enters the top main first. I tracked each rad pipe as it began to warm, going the length of the top main, then looping back along the lower main. However, the very end of the lower main did get hot before the heat looped back around to it... so at least some steam must enter the lower main from the boiler without first passing along the top main.

Steamhead

I think the boiler is piped wrong

With this type of main, the steam should enter at the higher end and the condensate should drain from the lower end back to the boiler. This means the steam must go all the way around the house to fill the main, but with a Gorton #2 on the lower end the steam will move quickly.

As it is now, air is being trapped in the middle of the loop by the steam entering at both ends. The only way for it to escape is thru the rad vents. I'll bet the rads in the middle of the loop heat rather slowly.

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Gnigamica

I think you are correct

The steam does travel around the whole main, and yes it does seem to move a little slowly along the second half... the lower half. As far as I could tell, the steam did not go the "wrong way" along the lower main... only the end of it heated, and this may have been convection from the metal above.



I will try to locate a heating contractor to tune the system without going so far as to re-pipe, I think. Your suggesting of a main vent toward the end of the lower main may be all that's required.



I did add airvents to the rads, by the way, since they were inexpensive. Hoffman #40s in the LR/DR (because they look nice), and Maid-o-Mist #5s everywhere else. They seem to be very effective. The most immediate effect is that the system is less noisy and no steam escapes from the rads.



Thanks for your time and assistance.