Vacuum type air vents

Jamie Hall

and I hope the real experts chime in...

But, to get started. Are you sure there ever were thermostatic elements in the outlets to the radiators? Not all two pipe steam systems used them -- some, particularly vapour, used orifices on the radiators to control flow. Provided the pressures are low enough, that works fine. That said, if they really are traps with missing elements, the system won't work properly at all until they are replaced. Can you get new elements? Replacement elements are available for quite a number of the old traps, and much cheaper than replacing the whole trap!

Your old boy's notions as to pressure are exactly right. However, no steam system would hold a vacuum forever, and air will get into the system -- that's what the main vents are for. Old systems fired on coal could, and did, run at a slight vacuum when the coal fire was banked. Unfortunately, neither oil nor gas firing works that way; when the burner turns off, it's off, and the system will quickly come to atmospheric pressure -- vacuum vents or no. Nice that the old boy remembers, though -- suggests that he may really know something about steam! Modern main vents do let air in when the burner stops. They also let it out in a hurry when it starts up again. Not to worry.

Somehow I have an idea that that 1948 boiler doesn't owe you anything, and may be costing you a lot in terms of efficiency, or lack of efficiency!

Pat_34

Vacuum type air vents/system--recommended by an old timer

I have a two pipe steam system. I have gotten Dan's book and have a much better understanding of how this system should work. I have found that my main vents need to be replaced and so far every steam trap that I have opened up to inspect is missing the theromstatic element inside. No wonder some of my radiators aren't heating...I am sure I have steam heading from one return line and shooting up other return lines trapping air in radiators and keeping the steam from heating them.

In my quest to fix this I am researching new steam traps. Not a cheap option but I want the system to work correctly. So now that I have Dan's book I feel like I can talk to the pros and figure out if I'm talking to a knowlegeable pro or a knucklehead. Already had one knucklehead (a personal friend) who visisted before I got Dan's book. (The first thing that knucklehead wanted to do was crank up the pressure!).

So I'm calling around town talking to heating/plumbing supply places and pros about installing new traps and I run into this guy who has been working as a heating contractor in our town on steam boilers since the days of coal. He sounds ancient on the phone and he knows about Dan and owns a number of his books.

On the phone last night he told me I shouldn't waste money on new traps. He said I should prevent any new air from getting into my system and rely on a vacuum to move heat. He said he can get my pressure down to 4 oz., use less heat/energy to fire my boiler and save me money. It all sounds good, but I don't have any idea why this would work to heat my system. It seems to take all the principles of basic steam heat and throw them out the window.

As I looked around the site I saw Dan's note about vacuum type air vents (http://www.heatinghelp.com/steam_systemproducingvacuum.cfm--the last topic on the page)and it sounds like that is what this guy wants to do in my system--create a vacuum so the water boils at a lower temperature and the heat is drawn around the system by vacuum pressure (I think). Dan says it won't work well with natural gas. My boiler is a 1948 American Radiator Co. IDEAL (300,000 btu) and it is gas fired. Will his approach work well with my system and if not why not?

Pat_34

Vacuum type air vents/system--recommended by an old timer

I have a two pipe steam system. I have gotten Dan's book and have a much better understanding of how this system should work. I have found that my main vents need to be replaced and so far every steam trap that I have opened up to inspect is missing the theromstatic element inside. No wonder some of my radiators aren't heating...I am sure I have steam heading from one return line and shooting up other return lines trapping air in radiators and keeping the steam from heating them.

In my quest to fix this I am researching new steam traps. Not a cheap option but I want the system to work correctly. So now that I have Dan's book I feel like I can talk to the pros and figure out if I'm talking to a knowlegeable pro or a knucklehead. Already had one knucklehead (a personal friend) who visisted before I got Dan's book. (The first thing that knucklehead wanted to do was crank up the pressure!).

So I'm calling around town talking to heating/plumbing supply places and pros about installing new traps and I run into this guy who has been working as a heating contractor in our town on steam boilers since the days of coal. He sounds ancient on the phone and he knows about Dan and owns a number of his books.

On the phone last night he told me I shouldn't waste money on new traps. He said I should prevent any new air from getting into my system and rely on a vacuum to move heat. He said he can get my pressure down to 4 oz., use less heat/energy to fire my boiler and save me money. It all sounds good, but I don't have any idea why this would work to heat my system. It seems to take all the principles of basic steam heat and throw them out the window.

As I looked around the site I saw Dan's note about vacuum type air vents (http://www.heatinghelp.com/steam_systemproducingvacuum.cfm--the last topic on the page)and it sounds like that is what this guy wants to do in my system--create a vacuum so the water boils at a lower temperature and the heat is drawn around the system by vacuum pressure (I think). Dan says it won't work well with natural gas. My boiler is a 1948 American Radiator Co. IDEAL (300,000 btu) and it is gas fired. Will his approach work well with my system and if not why not?

Pat_34

Thanks Jamie.

The traps did have thermostatic elements in them. I found one that still had it in and another thrown in a corner of the basement.

It's a bit discouraging to imagine replacing as many as 20 traps/elements plus main vents. Ugh.

The old timer is coming over early next week and I'll let you know what he says after he sees my system. Maybe I'll even take a picture with him and post it in appreciation of all the coal era contractors that are still on the job working with steam. These guys are part of an exclusive fraternity.

I wonder if I put an air vent with a check valve where the main vents are now that may help create a bit of vacuum pressure for the system. If it's operating at 4 oz of pressure the vacuum can't be that intense, but I don't know.

It'll be interesting to see what happens.

Unknown

Here's a couple of sites which may be of help to you as they has rebuild kits.

http://www.tunstall-inc.com/tunstallsteam.html

https://www.statesupply.com/steamTraps.jsp

Keith_44

I just updated a system just like yours earlier this year. The homeowner had a couple of local plumbers in who didn't really want to fully explore his system, so he called me and I convinced him to spend the money on making the system work perfectly.

I replaced every supply valve with a 1/2" Danfoss thermostatic radiator valve.
I replaced every return elbow (in this system there were siphon elbows instead of traps - clogged and rotted) with a suitable steam trap.
I replaced the two leaking main vents (vacuum type) with new Hoffman #75 main vents (atmospheric type).
I also discovered that a radiator that had been installed about 30 years ago had the supply and return lines crisscrossed and the radiator was knocking and barely heating.

This cost some money for the homeowner, but after I was done he was very happy with the results. So happy, in fact, that he referred me to his community board. The system was running at low pressure and heated the furthest radiator in about 12 minutes.

Hope you can consider some of these options for your home.