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Two pipe steam system converted to water with condensing gas boiler

bob eck
bob eck Member Posts: 928
can a two pipe steam system be converted to water system using a condensing gas boiler?

I know that the radiators need to have push nipples at the top and a tapping for a air vent.

Home owner has old oil fired steam boiler and would like to convert to nat gas condensing boiler.

he also has a 2nd home with oil fired steam boiler one pipe that he wants to convert to water system using a nat gas condensing boiler.

Has anyone used this to convert one pipe steam to water <a href=""></a> ?

One house has four apartments and last year 2010 - 2011 his oil bill was $6500 and that winter was a cold one and oil prices were lower than they are today. 

He has new insulated windows and insulation in the walls.

In this type of conversion what kind of energy saving can he expect.



  • Jamie Hall
    Jamie Hall Member Posts: 17,101
    Here we go again

    First, on energy saving.  If we make the assumption that the steam system has been properly maintained, or that it can be brought back to a state of good repair -- which is usually not all that difficult -- the maximum energy saving one could expect would be approximately the difference between a properly adjusted steam boiler and a similarly properly adjusted mod-con; that is, somewhere in the vicinity of 5%.a

    Now that does make the assumption that both systems are considered in a state of equally good repair.

    Second, on the conversion itself.  Yes, it is possible to convert many two pipe steam systems to hot water.  Is it a good idea?  Probably not.  To start with the radiators: they have to have both top and bottom connnections (most, but not all, do).  The valves for steam are unsuitable for water, so change all the valves.  The fittings on the outlets are unsuitable for water, so change all the outlet fittings.  Then check for leaks; what held on 2 psi may not hold quite so well on 20 psi -- plan on replacing a good fraction of the radiators because they leak.  Now consider the heaing capacity -- is there enough?  A radiator operating on steam will put out about twice the heat of one operating on 140 degree water.  Yes, you can raise the water temperature -- but you may lose the efficiency of condensing for the boiler, and thus any improvement in energy efficiency you might have had.  So plan on adding more radiation to compensate for the loss, unless the building is heavily and newly instulated.  Now on to the piping.  It is unlikely that the existing steam pipiing is laid out to accomodate any reasonable sort of hydronic piping.  Plan on replacing all the piping.  And there are other considerations...

    So... bottom line on it.  Why not spend the time to bring the steam system back up to speed, and the money on a modern steam boiler?  You'll be ahead of the game financially, and your quality of heat will be just as good, if not better.

    Converting one pipe steam to hot water is subject to all of the above, plus the hassle of the additional radiator conversions.

    Overall bottom line?  Fix your steam system.  It's easier and quicker, much less expensive, and sufficiently close in fuel economy that you will never recover the cost in fuel savings.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • icesailor
    icesailor Member Posts: 7,265
    2 pipe conversions:

    Oh Jamie,

    I beg to differ. Where I work, there was a heat guy, long ago passed, (who thought himself as a plumber and was always trying to find a licensed plumber to take out permits for him) used to convert two pipe steam systems all the time. All he did was remove the guts of the steam traps and install a circulator. It was supposed to work great.

    There aren't a lot of steam systems where I work, and I haven't ever asked around if there are still any of these "conversions" around.

    Understand that I don't want to sully the reputation of this late person. But, when he passed, a wholesale house stopped carrying "Soot Sticks" for cleaning boilers. He sold a lot of re-conditioned boilers that he took out of houses with failed boilers and installed new package boilers he just happened to have on hand.

    I thought once (Inot knowing any better) of trying it on a big house but decided that if it didn't work, I'd be screwed. I passed up on the job. The whole thing was ripped out and converted to FHW. I don't know if they used the radiators over.

    But, it is as simple as removing the guts out of the steam traps, adding a circulator, and hot water boiler controls. As easy as that.I sawe one the other way once. Some guy,got the contract to change the AC and boiler in a Post Office built as a WPA project during the depression. It was as most of them were, one pipe steam. The boiler was replaced. It didn't work. It was a nice HB Smith 2000 series boiler, connected up as water to the one pipe steam. That one didn't work. The Boss didn't get the job of fixing it. It was in courts for years over who would pay for it.
  • Jamie Hall
    Jamie Hall Member Posts: 17,101
    Kind of thought...

    that you would comment on this one!  I didn't say that it couldn't be done; it can, of course, and I imagine that some of the conversions work very well (no reason why they shouldn't, if a good man does the work and things don't leak).  My question, though, is why bother?

    To which, incidentally, I can think of at least one good because: because it is much easier to zone a hot water system than a steam system, and that could be a very good motivator.

    There is also a potential maintenance factor.  Much as we steam enthusiasts hate to admit it, there are a lot more decent hydronic guys out there than steam guys, and unless one is a bit of a do it yourself type, it can be hard to find someone to take care of, never mind upgrade, a steam system
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • furnacefigher15
    furnacefigher15 Member Posts: 514
    It may work.

    The part looks like it would work just fine, but let the customer know what there in for.

    The radiation surface area of the radiators may be inadequate during peak load.

    A radiator used for steam puts out more heat per square then it will with water.

    at 180 degree water a square foot is good for 170 btu

    at 212 degree steam a square foot is good for 240 btu

    Just make sure the load of the house will work with the reduced output btu. If not you will need more heat emitters.
  • icesailor
    icesailor Member Posts: 7,265


    You need to read what I said in another context. The late heater was known as one of the biggest hacks of all time. Whatever you saw him do, it would have been advisable to do the opposite.

    He had (though) a lot of innovative ideas. Like the fact that a Delaval or Hago 70 degree Hollow oil burner nozzle was THE universal nozzle and worked in all applications. Especially problem ones.

    I personally only considered it once because I had seen a job that he had done years ago. I decided as I said in the post, it had problems. After reading here what you, Steamhead and others have said here about the practice, I'm glad for all the reasons you all have stated that I never tried it. And it was only a passing idea.

    Be careful in reading what I say. There maybe another message in what I say.

    Someone once asked me what I thought of an idea he came up with. Not wanting to discourage him with his unique idea, I told him, That might work for you. I've never seen it work for any one else. But it might work for you. I ask, did I approve of his idea or didn't I? You need to be the judge. (Hint, I wouldn't have done it that way)
  • SWEI
    SWEI Member Posts: 7,356
    heat loss

    I suspect it would make far more sense to invest in some envelope improvements to trim that load.  Fix up the steam system, maybe add an ORC if needed. 
  • Steamhead
    Steamhead Member Posts: 14,842
    Best way for him to go

    is a wet-base steam boiler with a power gas burner. This will give 6-7% better thermal efficiency over an atmospheric boiler, and won't choke on the system debris that always seems to show up. I know you love your mod-cons, but this is not the place to use them. 
    All Steamed Up, Inc.
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • Mark N
    Mark N Member Posts: 1,090

    Just switching to gas will probably save 50% to 60%. Why go through the added expense of converting to hot water to gain maybe a few more percent.
  • icesailor
    icesailor Member Posts: 7,265
    Low Stepping:

    To step over a dollar to get to a dime.
  • Long Beach Ed
    Long Beach Ed Member Posts: 702

    Ah, the Power of Marketing!

    We're all pretty much on the same page with the technical details of converting steam to hot water.  But the question keeps coming up and answer doesn't change. 

    This is the power of marketing. 

    The customer hears of the nearly 100% efficient boiler and wants it.  Oh, but it doesn't work with his 55% efficient steam system.  Let's get rid of the steam system.  Can we convert it to hot water?  

    The fastest growing part of our business here is fixing those ultra-high efficiency boilers that other guys sell and can't get working right.  I go into homes and see the wall-to-wall baseboard covering those 1-1/2" holes that used to carry steam risers.  I see the condensing boilers flues cemented into unlined chimneys that gush condensate onto the basement floors.  I see zip cord miswiring controls.

    The repairs cost these guys more than they would save with that condensing boiler and mile of baseboard in a lifetime. 

    All they needed was to fix their steam system and insulate their attics. 

    Why didn't they?  Nobody markets steam heating repairs and insulation, that's why.  
  • SWEI
    SWEI Member Posts: 7,356
    agreed, mostly

    The great condensing boiler experiment has been a good experiment, on balance.  Over the course of the the past 15 years or so, we have all been driven to learn more applied chemistry and physics than they ever taught us in school.  In typical developing industry fashion, the path is littered with the corpses of products which failed to live up to their promises, or whose makers did not know how to support them, or to market them, or some other routine failing (which seemed so obvious to us at the time!)

    Does this mean we should give up on the entire concept?  Hardly.  We have a number of well-proven condensing boilers available right now and the industry is coalescing around those proven designs because the consensus is that they work well and are not prone to self-destruction.  When paired with proper controls and efficient emitters, the savings are significant enough to affect our national security.

    I remind myself that that the time-proven design concepts and ideas which we all use weekly day were all built on a foundation of field experiments.
  • bob eck
    bob eck Member Posts: 928
    Steam to water system

    Home owner now asking steam boiler is only 5 - 6 years old. Steam system working fine. He asked can he put a gas conversion burner on the boiler?
  • Long Beach Ed
    Long Beach Ed Member Posts: 702

    Almost certainly yes, if the job is done correctly.  The chimney may have to be lined, the boiler has to be cleaned and a new damper and spill switch installed.  The burner must be set up with the proper instruments. 

    Regardless of how the job is done, it may void the boiler's warranty.
  • Steamhead
    Steamhead Member Posts: 14,842
    What model

    is the existing boiler? 
    All Steamed Up, Inc.
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • Paul48
    Paul48 Member Posts: 4,470

    seems as though there is a lack of enthusiasm towards gas conversions. Something that I believe you will all see a flood of very soon. Maybe I'm wrong, but I wouldn't want to miss the short-lived opportunity, and have to try to play catch up.
This discussion has been closed.