Steam Heat

[Sempronia]

My boss lives in NYC and has gas-fired steam heat. He recently went to turn up the heat in his kitchen and the room filled with steam. He called his gas heat company and they found two bad air valves/vents and replaced them. What is the function of these air valve/vents? They cost $30 each plus labor. But what is their function and how and why do they go bad? Is there any way to tell if one is going bad before it actually stops working. Should all the others be replaced now in addition to the two that went bad? Is there any danger of injury when one of these air valves/vents goes bad. Can one be scalded by escaping steam?Any info will be appreciated. Thanks.John

[John SandersParticipant]

: My boss lives in NYC and has gas-fired steam heat. He recently went to turn up the heat in his kitchen and the room filled with steam. He called his gas heat company and they found two bad air valves/vents and replaced them. What is the function of these air valve/vents? They cost $30 each plus labor. But what is their function and how and why do they go bad? Is there any way to tell if one is going bad before it actually stops working. Should all the others be replaced now in addition to the two that went bad? Is there any danger of injury when one of these air valves/vents goes bad. Can one be scalded by escaping steam?: Any info will be appreciated. : Thanks.: JohnHi John. Yes steam 212 degrees can scald (actually water at 125 Deg F. can scald in less than 1/2second). Yes it is very dangerous when steam fills a room. Burning lungs come to mind as it is hard to breathe steam vapors, This is why in the Navy we learned to run down stairs (ladders) when a high pressure steam line ruptured. The Air vent is exactly what it is called a vent to allow air out of the system and was developed around 1913 by a Mr. George Hoffman I only use HOFFMAN Air vents (# 40 is the most commonly sold). You cannot have two objects occupying the same space.. Namely Air /Steam. The purpose of the AIR VENT is to allow the cool air to vent out of the radiator so the hot steam can replace the space the air was in. The parts of the air vent from what I can remember are the seat,tongue,base,nipple,float, shell and needle valve. This needle valve (small opening) allows the air to escape out of the system. Now the key to having a vapor system (steam) work properly is to get the air out ASAP BUT not to let any part become air bound. So to do it properly we use various size openings in the AIR VENTS. For example the smaller orifice is placed on the radiator closest to the boiler and the further away you move from the boiler the larger the opening of the vent. This is so you can vent the system evenly. Being from NYC I also see many types of steam heating systems one pipe two pipe and vacuum systems are just a few . You could make a career just on heating alone in NYC. The reason these things do go bad is imagine the thermo stress they are under from years and years of going above the boiling point then allowing to cool only to get burning hot again. Think about this, a part that cost under 10 dollars takes this kind of treatment year after year and is subject to no maintenance what so ever. How many cars last as long as this part? Personally if two did fail I would replace all of them AND find out why they failed. Just one pound of pressure PSI equals 216 degrees. This is called temperature pressure relationship and it is a major factor in heating & cooling systems. Ask your boss to have the pressure checked on his system and make sure his boiler gauge is calibrated properly.NYC water is slightly acidic which helps keep out plumbing system clean BUT when fresh water is added to a heating system this boiling of the water makes the acid more concentrated and leads to premature systems compared to a hydronics system (hot water heating closed system) Depending on the age of this system it should be checked for return condensate leaks and make sure the steam radiators are pitched back to the source properly as you want as much condensate to return back to the system as possible as Make up water does contain oxygen and this fresh water can ruin a system over a short period of timeGood luck and if I can be of farther assistance please feel free to contact me. Sylvan

[John SandersParticipant]

When the heat is off, the radiators fill with air. The vents are to let the air out so the steam can enter the radiator. When the radiator is full of steam the vent is supposed to shut off. The cheapest vents are single speed and probably not the highest quality. As you spend more, you can get adjustable vents that allow you to control how fast the radiator heats up.: My boss lives in NYC and has gas-fired steam heat. He recently went to turn up the heat in his kitchen and the room filled with steam. He called his gas heat company and they found two bad air valves/vents and replaced them. What is the function of these air valve/vents? They cost $30 each plus labor. But what is their function and how and why do they go bad? Is there any way to tell if one is going bad before it actually stops working. Should all the others be replaced now in addition to the two that went bad? Is there any danger of injury when one of these air valves/vents goes bad. Can one be scalded by escaping steam?: Any info will be appreciated. : Thanks.: John

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