should the end of a steam main be insulated?

Bigpickle18

I have 2 inch fiberglass insulation that starts from the riser all the way to the last branch on the main. the last 2-3.5 feet is uninsulated. I’ve done some reading and asked around and was told the end portion of the main should be left uninsulated because that’s where the steam needs to turn to water to return to the boiler, and to avoid having spitting main vents.

is any of this accurate? should they be insulated or left bare?

109A_5

Hello Bigpickle18,

Although it probably does not make much difference I would insulate it unless you like (or need) the heat that is given off in that area. if you don't need the heat there leaving it uninsulated just needlessly makes more condensate. The radiators should be the place where the condensate is made. If the vent at the end of the main is properly placed and the system pressure is correct it should not be spitting water and the main vent should close when the steam gets to it anyways.

Mine is insulated and I have no motivation to change it.

Mad Dog_2

If you have it, put it on, but I wouldn't go out and buy any more. Mad Dog

Waher

It’s better if it’s insulated for efficiency. The hotter the condensate returning to the boiler the less the boiler has to work to maintain a boil and less of a thermal sink for the boiler when it starts a heating call. Hotter condensate helps deoxygenate the water better and prevent the formation of corrosive carbonic acid. It’s a very slight efficiency boost if you are inclined, but not as critical as insulating a header or mains.

Jamie Hall

"told the end portion of the main should be left uninsulated because that’s where the steam needs to turn to water to return to the boiler,"

Well that's a new bit of baloney. Hadn't heard that one before… whoever said that to you is quite clueless about steam.