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some vent questions / ramblings

once again, thanks for the great steam resource. I have some questions regarding vents on steamer which has 2 main runs. The specs on run 1 are approx 25 ft 1.5 pipe connected to approx 12 ft 1.25 pipe that then ends at condensate drop. the main vent here is a hoffman model 16 vaccum. The specs on run 2 are approx 42 ft 1.5 pipe to approx 16.5 ft 1.25 pipe that ends in drop/also model 16 hoffman vacuum vent

Run 2 and corresponding rads are noticeably slower to warm by approx 15 minutes during 40 minute cycle. In addition to its longer length, run 2 has two 90 degree turns  vs run 1 w/  one 45 degree turn which I assume may affect steam speed.  I understand hoffman 16 vacuum is legacy vent not really designed for oil/gas systems (original to house 1929???) and neither run1 or 2 vent makes any noise during operation, so not even sure if they are doing anything. Still run 1 heats much faster.

Do you think replacing the main vent on run 2 (and possibly run 1) w/ a hoffman 75 is a good idea to try and correct slower warming? This seems like the best replacement vent as the old hoffman 16 looks to be a 3/4 size. The old vent seems pretty rusted in, I tested with standard wrench last night and it will need a pipe extender to remove. I thought about boiling in some vinegar if I can remove but assume probably best to just get a new main vent(s).

I am also considering replacing some radiator vents which are a mix of hoffman 1a, dole 1a, (both seem old) and newer USAV 884. I know usav is not a good vent but some rads on run1 have this vent and heat up quickly. I have noticed the rads w/ old hoffman 1a all seem to work well(but they are all on run 1). Anyway, I was going to buy at least some replacement hoffman 1as since they seem to be highly recommend (but pricey) and switch out usav vents on run 2. The goal is to increase overall efficiency.

any advice appreciated


  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    main venting selection

    i would replace the old hoffman 16's  with gorton 2's for a start. keep the old ones as christmas tree ornaments when polished up! if all goes well, there should be no difference in the heating up of each main vent at the beginning of a cycle.

    hoffman 1a's are my selection as they can be adjusted, and almost never wear out. keep your old vents in place until you have the main vents in place and working.

    the main vents do all the work letting the air out, and balancing the different mains by being fast.

    the radiator vents are only there to let the air out of the radiators/risers, so they can all be the same on a given floor [for starters].--nbc
  • conversiontime
    conversiontime Member Posts: 87
    gorton 2 height issues

    thanks for the advice nicholas, I did not know if the gorton 2 would be too much venting. looks like manual calls for 6 3/8 height, had no idea they are that big. Will need to measure if this will fit, how close to joists or other overhead obstructions can the gordon 2 go?
  • Steamhead
    Steamhead Member Posts: 16,732
    edited October 2012
    I'd only use a Gorton #2

    on the longer main. A Gorton #1 is all you need on the shorter one. The goal is to have the steam arrive at the ends of both mains not just quickly, but also at about the same time.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • conversiontime
    conversiontime Member Posts: 87
    low pressure gauge install and questions

    thanks for gorton2 advice. I used on both mains as had incorrectly calculated too short. all rads (many with new hoffman 1as) are heating much faster and evenly, great advice. Also re reading dans books, always good stuff if a little heavy on the math!

    I installed a 0-3 low pressure gauge tonight since the code 0-30 gauge seems unreliable. The pigtail on the pressuretrol was checked and cleaned anyway and seemed fine. The pressuretrol is set at lowest cut in .5 and cut dial near 1 (1.5 cut out). I have never noticed the pressuretrol shut down the boiler always seems to be thermostat that calls/cuts for steam. Installed new lpgauge on via the lwco which seems to be the best spot?

    The steamer ran for first 30 minutes and the new lp gauge barely flickered around .05-.1 mark this made me think something was wrong with either my install (too high?) or gauge but at the 40 minute mark the lp gauge showed .5, then moved to .7 pretty quickly at 45 minute mark before thermostat cycled boiler down.

    The system seems to run at a nice low pressure on a normal 40+- burn. After that sweet point pressure starts building pretty fast and assume that build continues yes? Or can a healthy system hit a certain equilibrium where it can run sub 2 psi for extended time?

  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,849
    Pressure increase

    I think your pressure went up because all your radiators were hot and therefor less able to condense steam. As the give off heat into their surroundings, they should be able to condense more steam, but at a lower rate. The pressure at this stage would depend on how well your boiler is sized.
    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
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