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Adding a two stage gas valve

DAS Member Posts: 5
Anyone have any pros or cons (warnings?) to adding a Honeywell two stage gas valve for low and high fire settings to our EGH 85 Weil-Mclain? (We'll also be adding a new Honeywell low range vapor stat with a relay.) Also, everything to be professionally installed.

Just got a call back from the manufacture's rep. He says it's not recommended. I guess that kills the project? Yet, I'd like to know people's thoughts...


  • gerry gill
    gerry gill Member Posts: 3,000
    we do it all the time..

    Here is how it was taught to me by a dead man..this is exactly how he would put it--'you find a control that does what you want it to do, and you put it on the boiler, and now the boiler will do what you want it to do'....he taught that it was up to the installer to ''make the boiler behave itself'' on the type of steam system you were putting the boiler on..see, the manufacturer is just giving you a boiler..they don't know what your doing with it or if its going on a one pipe system, two pipe system, vapor system, mini tube system, paul system, everyone is worried about lawyers tho..see thats the problem..old joe landed at normandy and his generation won ww2 with his attitude..hope that helps.
    Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

  • ttekushan_3
    ttekushan_3 Member Posts: 936
    cross posted at your original message

    Guess I should start reading at "strictly steam" before heading to the main wall!

    They recommend it for hot water but not for steam. Steam benefits from hi/lo firing every bit as much as hot water if not more. The trick is that the low fire manifold pressure must be carefully adjusted to prevent sporadic cooling of some radiators if the steam pressure is allowed to fall for a long period of time before kicking back up to high fire.

    Check out my reply at your original posting. I have more detail there.


    P.S. If Gerry says to do it -- do it!
  • Glen
    Glen Member Posts: 855

    As you are changing the burners configuration from factory certification and AGA/CGA certs, do you now have to call for field inspection by your gas inspector?
  • ttekushan_3
    ttekushan_3 Member Posts: 936
    Using the functionality already there is no problem.

    Some manufacturers of atmospheric boilers (like W-M, peerless, etc) utilize their two stage gas valves for this purpose, just the way multi-base designs can be used for similar effect. The only catch is, the manufacturers recommend it only for hot water heating systems since the heat distribution is not affected, being that the water is pumped. I think manufacturers don't want the hassle of offering it for steam boilers because the firing level and timing all affect distribution as well.

    It is really easy to adjust lo fire properly, its just that manufacturers probably aren't confident it will be done properly in the field. [With the exception of peerless, who package a steam boiler with three firing rates. Mod-u-pak gives three rates, which handle most contingencies without diddling with gas manifold pressures.]

    As such, enabling a function already provided by the manufacturer doesn't change the configuration of the gas train. Now, adding a maxitrol two stage regulator to the existing gas train components is a bit different. Its a good question, though, since we are not disabling or altering the existing active components in any way. Maximum fire and all safeties are fully functional.

    IMO, all steam boilers should have and always should have had this function, if for no other reason than to let the pick-up factor figured into the I=B=R ratings for steam to drop out once the steam distribution is established.

    I'm with Gerry on this, as introducing an extra regulator that lowers the firing level when triggered is so benign a change and so very useful.



    I won't address the bigger-than-life morass of legal and regulational implications of adding a small downfiring gas regulator to boiler as I'm liable to break into a tirade about knowledge, ability and principles being trumped by pathological manipulations of the law and our court system to serve an increasingly organized culture of legalized kleptomania. Won't go there. Nope. Not me...


    Further reading for anyone interested, expanding on the theory of why the low fire set point is important:

    Steam heating introduces the possibility of premature contraction of the volume of steam in the system if you turn down the fire too much or too soon, letting air back in --usually at the farthest reaches of the piping/radiation. The vacuum created by the condensing steam in the radiation already filled will keep the limited amount of "too-low-a-fire" steam going in their direction and maintaining a steam starved condition at the periphery of the system. Inadequate steam output at low fire will "lock" the heat distribution in its unbalanced state throughout the remainder of the cycle.

    Theoretically you can so thoroughly balance the system so that a steam volume contraction is even and has no net effect on heat distribution. The real world tends to be different. So: the system should be well balanced, the mains vented really well, and the low fire gas input level and vaporstat trigger point adjusted to maintain the trigger pressure. See Gill and Pajek's article on balancing steam systems using a venting chart- it on the Shopping page.

    Also, Boilerpro on this site has done a great article on using smaller boilers and even undersized boilers for steam- and how to get the distribution right. Its part of a larger issue of doing a "virtual downsizing" of existing oversized steam heating systems without touching or moving pipes or cast iron radiators. Good Stuff!

    And, if you haven't read every post by Steamhead and Gordo on this subject, you really should.
  • Steamhead
    Steamhead Member Posts: 14,324
    edited April 2010
    Thanks, Terry

    coming from you that means a lot.

    I don't have much to add here, except for this link which goes to an old thread describing what happened on one of our jobs. This shows the possible fuel savings from lo-hi-lo firing. The posts are scrambled but as far as I know they're all there.
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
  • DAS
    DAS Member Posts: 5
    Thank You!

    This has been an amazing thread, and thanks to each of you for taking the time and effort to set things straight for me. First, I'd like to mention Gerry and his concluding comment...

    "old joe landed at normandy and his generation won ww2 with his attitude".

    I happened to have spent last weekend in Washington, DC - visited the ww2 monument. It's a powerful experience paying homage to "old joe" and his generation. It seems to me, that Gerry's talking about taking responsibility and doing the right thing, rather than doing just for yourself. It means standing by your work, and contributing to the common good as joe did. Thanks Gerry. Thank you Joe.

    Next, I think is Terry. It appears that balance is the trick with low firing. We still need to put vents on the risers and slow down the radiator vents - the Boilerpro article was great! So there's lots of distribution work to be done. Also, I'll make sure our installer fully understands premature contraction. Thanks for the tips and comments, I very much appreciate it.

    And SteamHead, what was you mother thinking when she named you Steamhead? :-)) Thanks for the links. I'm working my way through them.

    I've learnt a lot from this exchange. Our five story Cooperative (Brooklyn), will probably wait until we've seen the effects of recent improvements to the system before moving ahead. Nonetheless, based on what I'm hearing, I see no reason not to plan for a two stage gas valve.

    Thanks guys!

  • Jim Pompetti
    Jim Pompetti Member Posts: 552

    Weils came with a two stage gas valves . We have even disconnected the second stage to stop short cycling . Even though the EDR called for the higher rate ,the system heated the house on first stage only. Give them a call they may give you an ok
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