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Steam radiator vents and explosions

So I have learned a lot lately about steam radiators, and how you don't actually have to live with them sputtering or banging all night.

I never knew vents were supposed to shut as soon as the steam reached them, but now I'm confused: if the boiler is running and every vent is shut, won't pressure continue to rise?

As a bonus question, I have read tutorials that say the vent should be sized in proportion to the radiator not the run length, but the maker of the vents say it should be based on run length. Is there a "right" answer to this? I'm just going to switch them around until it feels right.

Re: Steam radiator vents and explosions

The boiler will have its own pressure relief valve and temperature moderation system.

Re: Steam radiator vents and explosions

if you have a steam system what type of steam one pipe, two pipe, vacuum return Varivac , low pressure , high pressure there are many.I would suggest that you read a book or two on steam. As for vent they are used to get the air out of the system on start up after that the steam traps should work. The banging is where live steam meats cold condensate. Most boilers run on steam pressure not temperature. The boiler try to maintain a certain pressure that goes out to the rads where is the changes back to water (condendate) When this phase change occurs from steam to condensate a huge amount of heat is given off . Steam boilers are NOT to be played around with. If you do not know do not touch. call a plumber with a steam license or better yet a stationary engineer. Vents are sized just to let the air out, I like the manual type but some people like the auto vents by watts ect. In a house or small system the smallest should work however in huge systems larger one would be required. The guy that taught me Dan Holohan is the best look him up on the internet.

Re: Steam radiator vents and explosions

Thanks for the help. It's a one pipe system in a 3 story house. What books would you recommend?

Re: Steam radiator vents and explosions

One pipe steam is very special. I have only come across it once. some site that might help you

Btw do not let people that do not know about one pipe steam ever touch it, The time i came across one pipe a gaz company contractor said that he could change the boiler in a house easily to the home owner. the owner agreed and changed the boiler not knowing it was a one pipe steam system. when the contractor started up the system nothing worked. We were called in. Because the piping was inside the walls we had to live with one pipe. We then ripped out all the new piping and boiler Bought a new one pipe steam boiler and controls ect and started over , I think it cost about $20,000 everything in to the gas company. The system worked were nicely with control valves on every radiator. Lesson learned by the gaz company. The owner was lucky that the gaz company was responsible and not the contractor, the contractor would have walked away.


This is the bible for steam, see if you can find it, it is pricey maybe find it used or at a public library

The Lost Art of Steam Heating [Spiral-Bound]
Dan Holohan (Author


Re: Steam radiator vents and explosions

I don't know much about steam heat, but I do know this: for a one-pipe system, all pipes must be properly sloped. You want it all uphill from the boiler to the radiator. If there's any downhill slope at all, condensate (water) will get trapped in the low spot, then you'll get the typical banging noise as the steam pushes past the water. Look for any sagging pipes and support them maintain proper slope. Also look for improper repairs, and have a boiler tech fix it properly.

Even for a two-pipe steam system, you have to make sure the slope is correct both on the supply and the drain. It's not as important for a two-pipe circulated hot water system.

If a low spot is unavoidable, special condensate traps are available for installation in the low spot.

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