What Does Main Vent Do?

Steamhead (in transit)

you need a Gorton #2 vent on each main. If there are no vents or the existing ones are too small, installing the #2 vents will make a huge difference in the way the system heats up.

You might want to have someone experienced in carpentry open up the woodwork. Then, when the vents are in, they can put the woodwork back in such a way that it can easily be removed for future service.

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Mel_3

Do I need a Main Vent?

Since my system was reduced from 10 to 7 radiators, it has been short cycling, though all radiators get warm and eventually the thermostat is satisfied. I will shortly be seeking professional advice on down-firing. But in the meantime . . .

I notice that my system has no main vent. I don't really understand what a main vent is for. Perhaps someone could explain.

It would be very easy to install one where a pipe was disconnected off the steam main. Might that help with the short cycling?

Steam main is about 97 feet with 2.4" outer diameter.

Any advice would be appreciated.

Thanks,

Mel

Bob W._3

Mel, is your system one pipe or two pipe. If two pipe, does it have traps? Best to post some pictures of the system if possible. Someone here will answer your question.

Mel_3

Thanks Bob. It's a one pipe system, gas fired.

I could take pictures, but I'm not sure of what to take that would help. It's a pretty simple system.

Bob W._3

Mel, I strongly suggest you buy The Lost Art of Steam Heating, which will tell you what you need to know about how steam heating systems operate. That said, in a one pipe system, the mains are vented to allow the steam to replace the air in a very short period of time, which allows the steam to get to ALL the risers and therefore to all the radiators within about the same time. Your mains are fairly long (I assume you measured the entire main, including the dry returns?) so you could use some significant venting at the end of each main. If possible post pictures of the end of the mains where they go straight down vertically. Is there a Tee or other fixture there to place a vent? If so, you could vent there by placing vents up and back from that Tee, by using a 6-10" nipple for a riser. The preferred method is to mount the vents after the last takeoff to the last riser, up on a nipple. For your mains you would need a Gorton No. 2 on each one. Again, I suggest you post a few pictures and the steam guys on this Board will give you the right info.

Mel_3

Steam System

Actually, the system forks into two mains of about equal size at the boiler. Each is about 50'. The system terminates in a wet return back to the boiler.

I have no access to the end of the system without taking part of a finished basement down. I have never heard anything from behind the walls there that indicates there is any kind of vent. I assume from the positions of the covering woodwork and the pipe I can see that the wet return of one side joins the wet return of the other to flow back to the boiler.

The wet return does a great job of providing some heat to the finished part of the basement.

While the boiler is about 15 years old, I suppose the rest of the system was put in in 1939 when the house was built.

From the time I moved in (about 7 years ago) to the present there has never been a problem getting heat to all the radiators. I've worked on the vents to keep the system pretty well balanced.

Mel