Main Vent Replacement

hexago

Hi all,

I have a one-pipe steam system with a 3 year-old Burnham Independence boiler. I've had some hissing and spitting from a couple of radiator vents (Varivalves, also 3 years old). I lowered the pressure - subtractive pressuretrol main was set to 4/differential 1.5. I reduced it to 2 and left the differential at 1.5.

I have about 90ft of wet return around the basement with two mains, each with a main valve about 15 inches past the last supply line on each main
that I'm fairly certain are original (78 years) and likely need to be replaced. Are the two enough and what should I replace them with?

Also, had a guy out, who I'm fairly certain was a knucklehead, who didn't look at any of these factors and only declared that the wet return needs to be replaced. How do I know if it really does need to be replaced? There's a valve with a hose bib where the wet return meets the Hartford Loop and the water is black but there's no crud coming out.

dabrakeman

You should be able to set the ptrol at its lowest settings. If that creates problems then you have other problems. Your radiator vents could be hissing and spitting because they are doing too much of the venting if you do not have enough main venting. If with the lower ptrol setting you get a bunch of short cycling or some radiators don't get heat quick enough then likely you do not have enough main venting.

Is that a Gorton #1 on the end of an uninsulated main?

Usually best to provide some photos of your boiler and near piping. What is the EDR of the boiler and do you know your total radiator EDR? Have to understand how big your system is to know how much venting you should have.

Did the hissing and spitting just suddenly appear or has it been somewhat of a consistent issue?

Jamie Hall

You ask how to know if a wet return needs replacing. Simple. If it leaks. Otherwise, the worst it may need is to be flushed out, if the condensate returns slowly.

Steamhead

How long are those steam mains, and what pipe size?

hexago

I have about 70ft of 2" main on two runs; one is 34ft and one is 36ft. I was able to get a picture of the vent that's lodged in the corner. It looks like it is a Gorton No. 1. The second one on the other main is mounted horizontally though (?).

Boiler is an IN6I, which I think is sized correctly because the contractor that installed it painstakingly measured all the radiators three or four times. I'm having trouble finding a link to the EDR conversion sheet. All the ones I'm finding are dead. I calculated the EDR at 587, so 140K BTUs. Sound like the correct size, I think.

I just turned on the system for the first time since lowering the pressure and the spitting is gone and the hissing is greatly reduced. So it looks like I'm actually in pretty good shape. I'd just like to get the main vents working. No air came out of them (well, the one I can get to that isn't mounted horizontally) when the system is on. Should I replace with a Gorton No.2 on each since they're almost 40ft? And obviously add an elbow so I can mount the horizontal one vertically.

Jamie Hall

I'd go ahead and figure out how to mount a Gorton #2 on each main...

question

Forget the Groton 2 and purchase the faster venting Barnes and Jones Bigmouth.  They will vent better / faster than any other vent out there.  Right now you can order them on Amazon.  They actually cost less than the Gorton.  

Jamie Hall

The Big Mouth is indeed an excellent vent. Keep in mind, however, that it is slow to reopen on shutdown and does not close if there is water present. It's different -- but I'd hesitate to say that it's better.

JUGHNE

I have some BM's on almost 4' risers. They will pass a little water even at that height. No float inside to close them if they fill with water.

motoguy128

Big mouths also don’t open to break vacuum on shutdown. On larger piped vapor systems you can get whistling at radiator vents without a vacuum relief.

But OTOH, you get a lot of bang for your buck. Vent like two Gorton twos for less than half the price and are shorter. And have a union which can make for easier installation in tighter spots.