Main vent replacement sizing

mattkosloski

I have a residential steam system in my recently purchased home. I read "We got steam heat!" and it looks like one of the two main air vents (Hoffman 75) appears to have failed open. Date written on the side has it at about 14 years old, so not a huge surprise. I just wanted to make sure that's the right size vent before I go replacing it. I have two loops from my boiler:

• The short loop is 25', 1.75" pipe, currently has a Gorton #2. This feeds a 6 tube radiator with 18" plates x18.
  
• The long loop is 67', mostly 2.25" pipe dropping to 1.75" for last 18', has the failed Hoffman 75. This feeds one 6 tube radiator 18" x15 and a total of x35 36" 3 column plates.
  

It's a two story house the long loop serves all of the top floor plus a portion of the main floor. The upstairs has always been much hotter than the main floor, but I suspect this could be due to the failed vent. Thanks in advance.

KC_Jones

For the long main I would go with at least 2 Gorton#2 vents, 3 would be even better. What size tapping do you have to mount the vents on? I assume 3/4", but it's always good to check on it. A rule of thumb is 1 Gorton #2 for every 20' of 2" pipe. Your measured 2.25"...is probably actually measuring 2 3/8" if I had to guess, which is actually 2" nominal pipe. Your upstairs is probably hotter because your radiator venting is not balanced. Get your main venting in order and then you could work on your radiator venting and even things out. How is the system running otherwise?

mattkosloski

Overall it runs pretty well. There's some creaking a light water hammer but I figure that's mostly due to the previous owners sealing around the pipes through a few basement walls and lack of insulation. I'll be insulating the basement pipes and freeing up some expansion space.

The problem with going to multiple vents is right now I only have a single 3/4" mounting tap available where the existing vent is at the end of the return. I don't see any caps on the run other than a single large diameter (2"+) cap about half way through.

KC_Jones

You can install a single #2 vent, but you will have some imbalance between that main and the other. To install multiple vents you make a tree, see pics in this recent post. Just make sure the pipes on the "tree" have a little slope back towards the main.
http://forum.heatinghelp.com/discussion/153593/one-hissing-howling-radiator-convector-everything-else-finally-balanced#latest

mattkosloski

Alright great! I was never clear if you could stack them all at the end or if they were spaced throughout the run. I placed an order for 3 Gorton #2's and a handful of adjustable radiator valves. Thanks for the help.