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steam heat to fhw

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by NHFarmer, Feb 17, 2008.

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  1. NHFarmer

    NHFarmer Feeling the Heat

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    Like many others,This is my first post.I have been Lurking for a while and have gotten a ton of great info,Thanks to all. I have an old farmhouse with steam heat 1945 install.All cast iron radiators,I looked at a Tarm solo40 last week and am planning to insall one soon.The steam is a one pipe system and I would like to utilize the existing radiators for my hot water system.Is this possible?How about Zoning and temp control?any info would be great.Thanks

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  2. Eric Johnson

    Eric Johnson Mod Emeritus

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    Welcome to the Boiler Room, NHFarmer. I see you're selling a boiler. Is it wood-fired? Is it a steam boiler?

    I'm not aware of anyone making a wood-fired steam boiler for residential use. Converting a one-pipe steam system to hot water would be difficult, I think, though I don't know that much about it.

    I have cast iron radiators in my house, and I really like them, so I hope you can get something worked out.

    I'm sure someone around here can provide some sound advice.
  3. NHFarmer

    NHFarmer Feeling the Heat

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    The boiler I am selling is a Memco 1980 vintage 120,000 btu wood boiler for hot water.My new system will be forced hot water,I am thinking of repiping my radiators with two pipes for hot water.
  4. wdc1160

    wdc1160 New Member

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    NH welcome, I wish I knew more about the steam systems. I think some of the principles could be useful in our current approaches to space heating and heat storage. GL Bill
  5. Sting

    Sting Feeling the Heat

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    I can only add that the steam radiators are sized for steam heat. If used with FHW they will not be radiating nearly as much heat and will be undersized for the heat loss of the area that they were able to maintain on one pipe steam! Sorry to be the weapon of bad news. If your re plumbing for supply and return - do a heat loss calculation on each room and the available radiation. Add radiation or replace the current radiator with a unit of correct size. You may find it possible to move some and add some more!
  6. Eric Johnson

    Eric Johnson Mod Emeritus

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    For steam system conversions to hot water, I'd check out http://www.heatinghelp.com

    They talk a lot about steam heat on that site, and I know from lurking there that steam-to-water conversions is something they talk about on a regular basis.
  7. NHFarmer

    NHFarmer Feeling the Heat

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    Thanks for the info.I have not done any calcs yet but with the steam most rooms are too hot.steam is great heat but the whole house is on one t-stat it will overshoot temps real easy.uses waay too much oil,thus my conversion to wood
  8. Sting

    Sting Feeling the Heat

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    [​IMG]

    I know this reply will not endear me

    but

    Why not fix the steam - zone the house with non electric controls on each point of radiation to control overshots - and correctly control the boiler engine??
  9. Eric Johnson

    Eric Johnson Mod Emeritus

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    That's what they are going to tell him at heatinghelp.com. That and better insulation.

    All things considered, that may be the best option, as much as it pains me to say it. As I understand it, converting from steam to hw is difficult and expensive, and there's no steam option with wood boilers.

    That said, putting in a Tarm and repiping the whole system and radiators is something I'd be tempted to do.
  10. NHFarmer

    NHFarmer Feeling the Heat

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    problem is I can't run a steam sysem with a wood boiler.I am getting sick of buying oil and already cut wood for 2 stoves so wood it will be.I am going with the tarm in hopes of burning as efficiently as possible.I was hoping to reuse my cast iron radiators but I will have to repipe the system.
  11. Ncountry

    Ncountry Member

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    Something you may want to check also is where the bleeder valves are located .I installed a couple and then discovered bleeder valves were located 1/2 way up the radiator. Near impossible to bleed air out.
  12. Eric Johnson

    Eric Johnson Mod Emeritus

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    I'm curious about your radiators, NHFarmer. I just love cast iron radiators, which is why I think it might be worth the effort to convert your steam setup to hot water. Do your radiators have flow on both the top and bottom? In other words, is there a way for the water to flow across the tops of the rads? That's essential for use with hot water; some old steam rads only allow water flow across the bottom--there's nothing connecting the tops of the columns to each other. If you have a flow across the top (aka top "pipes") then bleeding won't be a problem, as you'll be able to screw a plug into the side vent and bleed them from the top.
  13. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    If you're willing to spend the money, converting the hot water can make a lot of sense.

    But there are issues if the radiators are the wrong size or not the right design.

    There are also issues if the existing piping has asbestos insulation, since it would really be best to eliminate the steam piping and just run pex, but you don't want to be ripping out asbestos-covered piping...

    As far as converting existing radiators... if they are over-sized (which sounds like it might be the case) and the venting is such that the air can actually be removed, and the design is such that you will actually get flow through the radiator (not simply across the bottom), they can be converted to hot water without too much work, as long as the plugs will spin out without breaking...

    The other option to keep a similar system but go completely to hot water, is to use panel radiators that are specifically designed for hot water systems. Might take up a bit more wall space, but nowhere near as much as baseboard. And without the high cost of underfloor radiant.

    The most practical solution depends on the current radiators and the budget for the job.

    Joe
  14. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    Also, just FYI, other than the oil usage, these are all repairable problems with the existing system. Things are not balanced right, and it sounds like you have a defective, mis-adjusted, or improperly-placed thermostat.

    Joe
  15. Eric Johnson

    Eric Johnson Mod Emeritus

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    Here's an old steam radiator without a top pipe. I figured out how to make it work well in my hot water system, but that wouldn't be a practical approach in your case. If yours look like this, in other words, then it's back to the drawing board.

    Attached Files:

  16. NHFarmer

    NHFarmer Feeling the Heat

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    I just checked all of my radiators,they have 2 taps top and bottom and a small screw plug at the top of each.Also the tops of each are connected together so I am guessing that they should work?That would be great.I won't talk about the existing pipe covering but I am thinking about abandoning the old pipes and run new pipes,maybe Pex? Question is the way they were piped will leave me with feed in-feed out pipes in the cellar,can I manifold them in the cellar or do I need loops on the second floor.I don't mean to ramble but I also don't know how to pipe the radiators,feed in bottom return in top?thanks
  17. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    Yes, those should work, from a hydraulic standpoint. As long as the sizing is sufficient, and the plugs come out without breaking, you should be fine.

    Pex is a good choice for a retrofit. Or for new construction, for that matter, but it is particularly useful in retrofits.

    You can have a manifold in the cellar, and run a pair of pipes (supply and return) to each radiator. That's called a parallel or "homerun" system. If designed properly, you can put a thermostatic valve on each radiator, allowing for individual room temperature control.

    Usually supply into the top, return out the bottom. You may want to use some copper at the top connection, down to the floor, before converting to pex, for aesthetic reasons (pex isn't exactly pretty).

    Joe
  18. Eric Johnson

    Eric Johnson Mod Emeritus

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    All my rads are piped bottom to bottom.

    If you're concerned about the plugs breaking the radiator casting when you try to extract them (steam rads tend to corrode while hot water rads usually don't), there are other, more labor intensive ways to get them out safely. Specifically, chemicals, heat, drilling--in that order. I've had a lot of luck with a drill, hacksaw blade and a cold chisel.
  19. NHFarmer

    NHFarmer Feeling the Heat

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    sounds like I have a plan but I am not familiar with the thermostatic valve?
  20. solarguy

    solarguy New Member

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    steam radiators are sized to operate at 215 degrees.

    If you have a fax number, I'll copy & shoot you some stuff out of an Ashrae book on measuring radiators & the correction factors for operating at different temperatures.
  21. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    It's a thermo-mechanical valve that you attach to the radiator piping. It has a wheel like a thermostat that lets you set the desired temperature. Then it modulates the flow of water to the radiator in response to the difference between the desired air temperature and the actual air temperature.

    Joe
  22. sled_mack

    sled_mack New Member

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    Yea, but.... If the house is older everything was probably oversized enough that he'll be OK with 180 deg water. And, if the house has had any insulation/window improvements over the years, that is even more in his favor.

    I'm not saying the numbers won't be good for him to have, but he needs to think about other factors before getting scared off. Like, on cold nights, do the radiators keep up? Do they keep up with ease, or struggle to keep up?
  23. Eric Johnson

    Eric Johnson Mod Emeritus

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    Is that the same thing as a TRV, Joe? I have two of those (1/2-inch) but no idea how to use them.
  24. solarguy

    solarguy New Member

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    I don't know Sled_Mack, I assume nothing until the final numbers roll out of the calculator.
    Engineering is nothing more than an educated guess thru the use of mathamatics......
  25. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    Yup. Thermostatic Radiator Valve.

    Joe
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