Replacement recommendations for main valves?

susieville

We live in a two-family house with two separate one-pipe steam systems; the "old" boiler which heats our tenants' apartment is a Capitol snowman, converted from coal to oil to gas, with no Hartford loop.  The "new" (our apartment) is a Robert-Gordon 2G4 boiler.  Each system has two main vents, a No. 5 Hoffman quick vent float air valve, and a No. 4.  Our system is working beautifully but our tenants have been complaining that their radiators are loud (hissing).   A few years ago I replaced all the radiator vents in the house with new Dole 1-A Vari-Vents, and so I'm thinking those are probably not the problem, and instead maybe their main vent(s) are blocked.  What modern vents would you recommend using to replace those Hoffman main vents?  I found a No. 4 on line, but can't find a Hoffman No. 5.

Also, if I'm obviously barking up the wrong tree, please let me know! 

Many thanks!

BobC

More info?

First we need a little more information, how long are the steam mains for this apartment and what sixe is the steam main (circumference is fine). I know the Hoffman #4 is rated at 0.06CFM and that is very low for a main vent, I'm not sure what the #5 is rated at.



Bob

susieville

Measurements

Hi Bob- The riser from the top of the boiler goes to a tee, with one line then extending 24' to the #4 vent, and the other 40' to the #5.  The vertical riser is 3.5" OD and the main lines are 2.5" OD. 

One more observation: when I went down there to measure, their boiler had just come on, and I listened carefully to each vent a few times and never heard any air coming out.  It was boiling hard and the pipes heating by the time I came upstairs.

Thanks again!

BobC

Try this

The 40 ft 2"ID main has about 0.87 cu ft of air in it and the 24 ft 2" main has about 0.52 cu ft of air in it. We would like to get rid of that air quickly so I would suggest a Gorton #1 (0.33 CFM) on the 40 ft main and 2ea  Hoffman 4A (0.13 CFM) on the 24 ft main (mount them on an antler) for balanced venting. You could just replace both with the Gorton #1's (Maid O Mists #1 would be about the same) and hope the imbalance sorts itself out.



All of these vents have 3/4" male threads on them; you should use some teflon tape on the threads before installing them.



Bob

susieville

Thank you!

I'll try it and let you know.  Thanks a million!

Hap_Hazzard

#4 & #5

Bob, I don't think the numbers Gerry and Steve give for the Hoffman #4 are correct. I've never tested one, but there are cross references that give a Gorton #1 as a replacement. There is also a Dole #4 that looks identical. I used to have one of these, and it was very slow until I soaked it in vinegar, then was close to a Gorton 1. Apparently these things didn't tolerate water. They don't have floats, so they spit and fizzle and the scale builds up really fast. My hunch is that Gerry and Steve tested a used one.



I've never heard of a Hoffman #5 either, but there is a Dole #5 that cross-references to a Hoffman 75. I know I'm taking a leap of faith there, but if you substitute a Gorton 1 for the #4 and a Hoffman 75 for the #5, the venting rates make sense.

BobC

4, 4a, or 75

I had a Hoffman 4a on my main many years ago and i replaced it with a Gorton #1 and that vented a lot faster. Now that 4A may well have been partially blocked with calcium so I don't know that it was working correctly because it wouldn't fully close when I replaced it. On top of that it was a 4A not a 4 and I really don't know exactly what the exact difference in venting rates are between them.



I didn't suggest the 75 just because they are so expensive, I think you can get 3ea Gorton #1's for the cost of one #75.



It sounds like both her vents are paper weights at this point so a Gorton #1 is sure to be a lot better. She could always put 2 #1's on the long main and a single #1 on the short one.



Bob

Hap_Hazzard

4A

I think the 4A is just a 4 with a float, but I've only seen pictures.



I didn't mean to make it sound like I was recommending a Hoffman 75 as a replacement, just as a clue to what the dead man's intent was. I probably should have said substitute instead of replace. I agree with you about Hoffmans vs. Gortons, and by using 2 #1s instead of one larger vent, they only need to keep a spare #1 around in case any of the main vents fail.