What will happen if I add a Air vent on a Two-Pipe Steam System?

Dairon421

So I went to a house today and found steam vents on a two steam system with steam traps. Will that effect?

Jamie Hall

Oh dear. Well, it depends on where the vents are -- I presume you mean they are on the radiators. Won't really do that much harm, except make the system much harder to balance. It is possible that, since you no longer can ocunt on any steam pressure in the radiators, that there may be some problems with condensate return being slow.

jumper

Somebodies installing radiator vents on trapped rads has been seen before. Does extra air go through the traps ?

Dairon421

https://youtu.be/NiDZOOuc13U
I just watched this video. It will effect the system if the radiator trap fails open

Jamie Hall

Yep. And a failed open trap will affect the rest of the system very badly.

Bourasque

If you install an air vent on that two-pipe radiator, the air will get out, and the radiator will heat, for sure! But since there's steam in the return lines (because of the failed traps), the condensate won't get back to the boiler until the end of the cycle.

Steamhead

Someone obviously didn't know what they were doing. The air in this system is vented at one or more central points in the basement. Fix the bad vents or traps and remove the radiator vents.