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converting two pipe steam to hot water

RJL
RJL Member Posts: 2
This would be my first conversion steam to hot water. The only issue I see I am concerned with is venting the radiators. The radiators do have push nipples at the top so they go all the way thru but I do not see any place for an air vent.

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 20,432
    And why would you be wanting to do this at all? A steam system, once properly maintained and the de-knuckleheaded, is at least equal to hot water in comfort and is a lot simpler...

    There are other issues (at least) to consider in addition to adding air vents to all the radiators: you must pressure test them and all the associated piping as well, and, if you are not repiping the whole thing, making sure the piping will hold pressure, and also removing any traps or other fittings and any orifices or other restrictions on the radiators.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    1MatthiasGBartIronman
  • Steamhead
    Steamhead Member Posts: 15,755
    edited June 2018
    Don't do it. There are two basic problems:

    1- a hot-water radiator will only put out 2/3 the heat of the same size steam rad, which often causes inadequate heating, and

    2- hot-water needs over 10 times the pressure of steam to operate. This higher pressure WILL find any weak points in the system and result in leaks.

    And the supposed fuel savings? Don't count on it.

    Here is one such discussion:

    https://forum.heatinghelp.com/discussion/145002/actual-savings-over-steam-heating
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
    1MatthiasGBartIronman
  • ScottSecor
    ScottSecor Member Posts: 642
    Steamhead, I am not trying to be argumentative, but wouldn't you agree that most steam radiators are typically much larger than they need to be? Especially since most homes have better insulation, windows, doors, etc since they were built roughly a century ago?

    With regard to the fuel savings, potential leaks and maybe just as important for us is the pump issues we face with hundred year old pipes and radiators that are likely coated with some rust.
  • Steamhead
    Steamhead Member Posts: 15,755

    Steamhead, I am not trying to be argumentative, but wouldn't you agree that most steam radiators are typically much larger than they need to be? Especially since most homes have better insulation, windows, doors, etc since they were built roughly a century ago?

    With regard to the fuel savings, potential leaks and maybe just as important for us is the pump issues we face with hundred year old pipes and radiators that are likely coated with some rust.

    You never know what's been changed around in that time. I've seen homes where some or all the radiators have been replaced, as I'm sure you have.

    Besides, if this is 2-pipe steam with water-type rads, it's probably Vapor. Vapor is still one of the best systems out there. Very often, the rad valves on Vapor systems will leak if you try to use them with hot-water. And, with all the work going on to resurrect the lost art of vacuum steam, an existing Vapor system is a great vacuum retrofit candidate.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 13,111
    Converting steam piping to water to me is just kicking the can down the road. Either leave it steam and fix the system or rip and repipe. Nothing wrong with steam if done right.
  • GBart
    GBart Member Posts: 746
    There is only 1 way to do it right even though you shouldn't do it, rip all the pipe out and run pex properly sized for each load, in many cases all you'll need is 1/2", ZONE THE HOME- in many rooms you may be running to 1 radiator , DO A LOAD CALCULATION, properly size the boiler, install OUTDOOR RESET so the water temp matches the load, you don't need 180-200 degree water on any day above 40F.

    This actually works great, I did it on a 100+ year old house I had but it was hot water, I ripped all the giant black pipe out because it was a waste, heating all that water cost 1-2 circulator cycles and $$$$$.
  • RJL
    RJL Member Posts: 2
    From what I am reading you advise not to do this. I would like to say I did a heat loss calc and yes the radiators are big enough for the current load. We do have a few customers with steam, not many. Most are one pipe. I have read about the vapor systems with two pipe. How does one tell if it is a vapor system. This system has stream traps at each radiator and one main vent at the end of the return at the boiler.
    Ryan
  • Tinman
    Tinman Member Posts: 2,797
    I’d agree with Steamhead and Jamie for the most part but there are always exceptions the way I see it.

    I did a conversion at a church a few years ago using 2 10:1 modcons and a PAP homerun manifold system. It worked out great. Gas bills went way down, Church is comfortable. There are times in the shoulder seasons where only one boiler is firing at 20%.

    Originally, the place was so over-radiated and the boiler size was almost double the heat loss. There were also 100’s of pipe patches throughout the building. The steam system was never maintained right.

    Of all the radiators, I had one leaker.
    Steve Minnich
  • Jamie Hall
    Jamie Hall Member Posts: 20,432
    @RJL -- the combination of the trap configuration and the one main vent on the end of the return makes it almost certain that it was a vapour steam system. That's how they were done.

    If that is the case, then the best move would be to work on restoring it to its original operation -- which won't be hard. First off, you can use the existing boiler, unless it is wildly oversize (measured by EDR, not building heat loss!), but you will need to put a vapourstat on it in addition to the pressuretrol. Second, you need to check all the traps -- especially those traps at the ends of the steam mains to the dry returns (called crossover traps). If you find some which aren't working, it's usually pretty easy to replace the working element. Third, you should assess that main vent. It's critical. If you are in doubt about it, best to replace it; how big a vent or vents you need we can help you with. Then, chances are folks have fiddled with the valves on the radiators; you will want to go around and adjust them so each radiator is heating the space to the degree desired. Best done on a colder day...

    And that's it, unless you have some big leaks...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    1Matthias
  • Henry
    Henry Member Posts: 995
    We do a conversion about every 2 to 3 years. You pull out the steam trap guts including the seat. One drills and taps an air vent near the top of the cast iron rad. Remember that the cast iron rads were sized for windows open. So they are grossly oversized. One can now size the boiler according to the actual heat load. Mod/con work great! As for leaks, most conversions don't and the few that leak are in the basement. The energy savings are 50 to 70%. It is simple to calculate using outdoor reset as only here, 100 hours are used for -20F design temperature.
  • Henry
    Henry Member Posts: 995
    Perfect
  • ChrisJ
    ChrisJ Member Posts: 13,881
    edited June 2018
    Henry said:

    We do a conversion about every 2 to 3 years. You pull out the steam trap guts including the seat. One drills and taps an air vent near the top of the cast iron rad. Remember that the cast iron rads were sized for windows open. So they are grossly oversized. One can now size the boiler according to the actual heat load. Mod/con work great! As for leaks, most conversions don't and the few that leak are in the basement. The energy savings are 50 to 70%. It is simple to calculate using outdoor reset as only here, 100 hours are used for -20F design temperature.


    Just to be clear, they were often sized to have A window cracked in each bedroom, not "windows open". Ever opened even one window wide when it's -20F out?

    Second, if you believe converting from one fluid to another saves 50-70% ODR or not, I've got some things I'd like to sell you.

    This comes from converting an old, broken, improperly working steam system to hot water.

    Does hot water with ODR save energy and increase comfort? Absolutely. Just not 50-70%.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • jumper
    jumper Member Posts: 1,911
    ChrisJ said:

    Henry said:


    Second, if you believe converting from one fluid to another saves 50-70% ODR or not, I've got some things I'd like to sell you.

    In the seventies I was involved in several steam to water projects. Turned out to be more expensive and complicated than anticipated each time. Nowadays two pipe steam can be improved both comfort & energy wise with thermostatically controlled valves on each terminal. Staged combustion also improves operation. These improvements are easier and cheaper than abandoning steam for HHW.

  • Jamie Hall
    Jamie Hall Member Posts: 20,432
    I have never had much trouble accepting that it is possible to increase heating efficiency as much as 10% by converting either a properly working steam or hot water system to a fully controlled modulating/condensing, outdoor reset controlled hot water system, provided that the system is sized so that the boiler can always run in the condensing mode.

    However, the claim that one can increase the efficiency 50 to 70 percent can only be backed when one is comparing an old, poorly maintained system, on the one hand, with a new all the bells and whistles system (which may be either steam or hot water -- it doesn't matter) on the other. This is the same kind of false comparison as comparing the fuel efficiency of my 1994 big block Chevy K2500 with my son-in-law's 2017 Duramax turbodiesel Chevy K2500. It does a disservice to the customer -- to be nice about it.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Steamhead
    Steamhead Member Posts: 15,755
    Henry said:

    We do a conversion about every 2 to 3 years. You pull out the steam trap guts including the seat. One drills and taps an air vent near the top of the cast iron rad. Remember that the cast iron rads were sized for windows open. So they are grossly oversized. One can now size the boiler according to the actual heat load. Mod/con work great! As for leaks, most conversions don't and the few that leak are in the basement. The energy savings are 50 to 70%. It is simple to calculate using outdoor reset as only here, 100 hours are used for -20F design temperature.

    Says the guy whose "actual savings" turned out to be no more than my company got by fixing the steam:

    https://forum.heatinghelp.com/discussion/145002/actual-savings-over-steam-heating

    Nice try, Henry.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • Steamhead
    Steamhead Member Posts: 15,755
    RJL said:

    From what I am reading you advise not to do this. I would like to say I did a heat loss calc and yes the radiators are big enough for the current load. We do have a few customers with steam, not many. Most are one pipe. I have read about the vapor systems with two pipe. How does one tell if it is a vapor system. This system has stream traps at each radiator and one main vent at the end of the return at the boiler.
    Ryan

    That's correct, @RJL . You're going down a dangerous path if you do.

    We've been asked to look at a few buildings over the years that had such conversions. In every case there were issues- leaks, uneven heating, etc. There is a particular contractor here that pushes these conversions and walks away when things don't work right. Our response is to undo the conversion and take the original contractor to court. Otherwise we don't touch them- too much liability risk.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
    1Matthias
  • Tinman
    Tinman Member Posts: 2,797
    I don’t push conversions, quite the opposite. I have had a radiator or two leak and there’s the “our radiators aren’t as hot as they use to be” truths that I explain before and after. But, I can say with 100% certainty that the savings st that church is more than 10%, I went from a 750k steam boiler to two cascaded 199k modcons.
    Steve Minnich
    Henry
  • Tinman
    Tinman Member Posts: 2,797
    As far as balance, every rad supply and return were piped backed to manifolds with valves and flow meters, easy to dial in.
    Steve Minnich
  • Tinman
    Tinman Member Posts: 2,797
    There’s no doubt that a properly installed, well-maintained steam boiler/system will outlast a mod con boiler so there’s that. There’s also carbon footprints.
    Steve Minnich
  • The Steam Whisperer
    The Steam Whisperer Member Posts: 1,084
    A big part of saving fuel in a steam system, once you get all the years of accumulated problems fixed, is eliminating the need to put in a boiler matched to the oversized radiators. Then add to the top of that almost all boilers are grossly oversized even when checking the radiation ( typically we see about double the radiation size, not the 1/3 used that is the recommended pick up factor).

    If you have a typical good gas atmospheric steam boiler ( about 80% thermal efficiency) here's what you end up with for expected seasonal efficiencies when sized as shown:

    Building heatloss = 100% 72%
    Typical oversized radiators = 100% x 1.6 = 160%
    Typical conventional sized boiler with 33% pick up= 213% 61%
    Typical oversized boilerand radiators = 213% x 1.6 = 340% 54%

    This is based on National Bureau of Standards testing for atmospheric hot water boilers, which I would expect to be pretty close to steam boilers too. I have some success using this test data for predicting potential fuel savings due to boiler size changes.
    With two pipe steam, you have the unique advantage to be able to effectively resize your radiation load on the boiler by using supply valve orifice plates to meter the steam and then downsize the boiler accordingly. For most systems that works out to going from 54 to 58% seasonal efficiency up to about 70% or about a 20% drop in fuel usage. Stepping up to a power burner boiler that tends to have a lot less standby losses and burns fuel more efficiently, you can bring the boiler seasonal efficiency up to probably close to 78%, another 9% drop in fuel usage.
    Th next step up you can take is then use outdoor reset to reset steam pressures most o f the year and combine it with a modulating burner that will spend most of the year at 60% or less load. Boiler efficiency creeps up again just like in outdoor reset hot water boilers. The big gains here, however, are probably system efficiency and reduction in building heat loss due to cooler air temps at ceilings and less air leakage most of the year.

    We had a building a few years ago with a 2 pipe vacuum system with two high/low boilers...one at 2 million/ 1 million input and a second at 1 million/ 500,000 input ( 3 million btu/hr total capacity)
    We retrofitted most of the radiation in the building with Orifice plates and after getting into the heating season we could run the smaller boiler at 500,000 input for all but the coldest days. This
    gives you and idea of just how great the fuel savings can be with some basic upgrades of most two pipe steam systems.

    To learn more about this professional, click here to visit their ad in Find A Contractor.
    ChrisJTinmanCanucker