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Converting steam convectors to forced hot water

Hi all,

I searched around the last few days on this but did not find any thread addressing a few of my concerns.

Working in an old new England home with an existing steam system using copper convectors that are buried in the walls. Primarily on the first floor on the second floor. Addition on second floor roughed for sf30 bb. The convectors have no vents on them. The system is piped in what I believe is a reverse return. There is a 1.5" supply header around the perimeter and a 1 1/4" return around the perimeter with each convector supply being 1" and the return 3/4". The return breaks into 4 vertical pipes with steam vents into the floor and back to the boiler.

We want to convert to fhw for several reasons...mostly to gain efficiency, run the superstor and use bb on the second floor.

My main questions are:

1. Boiler location is moving...20ft or so. What size piping should I plan on using to hit the existing supply and return for the first floor convectors. Should i pump away as we usually do now?

2. 3 convectors have to move outward (for the addition) about 12ft each. Can the mains stay in there current location, (old foundation location)? That would mean each supply and return to the 3 moved convectors would be 12ft or so. All are currenting right near the mains. I think this is ok as the water will be forced through no matter what right. I really don't want to reconfigure the main return and supply. Also planning on using the same size piping as on the other convectors. I am thinking iron on the convector side so that I can secure them nicely, then connect the two with wirsbo heat pex.

I tried to get the homeowner to change to bb for the first floor, had him convinced, and now he's back to keeping these convectors! It's a loosing battle.

Should I be worried about leaks in the existing piping ? Everything worked fine with the steam. I know I have to remove the steam vents on the return main.

Am I missing anything?

Thanks all, to date I have not performed a steam to fhw conversion so I want to make certain everything is going to work well.

The boiler I plan on using is a lochinvar, piped with a primary secondary, 3 zones...superstor, 1st convectors/iron piping with one 2nd floor convector, 2nd floor new bb

And a future. It is not ideal to Have the 2nd floor convector stay I realize...but it is in an existing section of the home that no one wants to get into the walls in. Otherwise I would put bb in there and tie it into the 2nd bb loop as it should be.

Thanks in advance!



  • jumperjumper Member Posts: 990
    why save risers ?

    If your doing all this why not use all new flexible pipes ?

    If you're moving convectors just pressure test them.

    Not that you asked, but original design sounds innovative to me.
  • SteamheadSteamhead Member Posts: 11,373
    That sounds like

    it might be a Trane Orifice system, where the orifices are cast into the convectors. If you try to run these on hot-water, the orifices will cause a lot of noise. Don't do it.

    Then there are the other reasons conversions are not such a good idea- possible leaks, insufficient output etc. Don't forget, you will be liable if anything goes wrong.

    And once again, where are the scientific comparison results that say steam is less efficient? This keeps coming up, but without the numbers it's just talk.

    Leave the first-floor steam convectors and their associated system alone. Remove the one on the second floor and pipe the entire second floor as a hot-water baseboard zone, which will also let you control it individually. If the steam boiler has enough capacity, you can run the baseboard and SuperStor off of it. If not, add whatever boiler you need to do the job.
    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.
  • Convector style

    I believe that the existing convectors are Young type b style L and are listed for use with steam or hot water. The existing steam boiler is a serious pos and needs to be decommissioned. And with this homeowner....I am along for the ride. I will double check but I don't think there are any orifices in these.
  • Keeping headers

    With the convectors (about 9) on the can't just go in and out of them...the head pressure would be so great you'd need a huge pump. Using the existing reverse return oversized iron seems like the best solution and is a high mass system that a new lochinvar should love and I would be able to use a standard gringos 3speed. I thought about using pex for a new loop connecting the convectors, but that requires almost the same work as just running new bb. And I would need at least one monoflow tee per convector.
  • Re:

    Grundfos pump. Darn auto correct! Yes this was a nicely laid out system and was installed by a true craftsmen! Everything sized and pitched just perfectly. We are so spoiled these days with pex and PVC and sharkbites! ;-)
  • HenryHenry Member Posts: 720
    Steam to hot water

    We performed the conversion on a large luxury apartment building, last fall. We kept the trap bodies and removed the seat in them. We drilled and tapped an air vent on each radiator. We replaced some of the return horizontal lines in the basement. We had only one leak on a return riser on the first floor. It was due to be changed anyways. We used variable speed Grundfos pumps on the main loop.

    The savings using degree days are enormous. With a 13% colder winter, energy consumption is less than half! All the occupants mentioned that the heating was now much more comfortable and more even in the rooms.

    We do at least one steam conversion a year, mainly commercial buildings. It cannot be done on one pipe systems but can on any two pipe. Remember that the cast iron steam radiators were always over-sized. Therefore, there is no problem with lower temperature hot water compared to steam.
  • jumperjumper Member Posts: 990
    steam conversions

    Good to see you ,Henry, back posting here. Knowledge and techniques must have improved over forty years. The steam to hot water conversions we did in the seventies always ran into glitches.

    As for energy efficiency, where does the wasted energy go ? In the boiler room you can recuperate what goes up the stack. Phase change is inherently more efficient than liquid temperature drops. Despite what US DOE says.
  • SteamheadSteamhead Member Posts: 11,373
    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.
  • jumperjumper Member Posts: 990
    remember that thread well

    And others like it. Some points are overlooked.

    First the converted involves modern improvements and that is compared with the old and probably underserviced old steam system. There are improvements that can be made to a steam system that are cheaper and less disruptive than converting it to hot water.

    Another is that there are other costs in addition to fuel. For example, with 400 hot water radiators how often do you expect a leak ?
  • Questions

    Thanks for all the input.

    My specific questions still remain...

    The steam vs hot water is of no concern to's getting converted one way or another.

  • Charlie from wmassCharlie from wmass Member Posts: 3,922
    If you want to convert

    and waste the time and money. Then you need to check for orifices and remove them. You need to size your feed and returns to suit the load. As a professional I am sure you already have the charts. You also need to do a room by room heat loss and make sure the convectors will heat the room with the derated outputs you have from hot water. Again just use your charts. You also need to hope the system will take the 12 to 15 psi as opposed to the 1 psi of steam. Make sure to add hangers if they are sparse on your iron feed and return as water weighs down the pipe more then the steam did.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • Orifices

    Thanks Charlie,

    Can someone enlighten me on orifices and where they are in the convectors.

    These are trane, la crosse Wisconsin. I have taken some apart down to the cast end...nothing in the piping connection. Is it under the 3/8 caps on the ends (4)?

    I did just have a heat calculation done and the old convectors are more than okay with 180f. I may run a lower target for most day time temps.

    According to lochinvar the near boiler piping can be 1" or 1 1/4" based on load even though it's going into a 2" main.

    One other thing I thought of I going to be able to purge all the air out with a reverse return? There are no bleed valves on the convectors and there is no way to add them....they are in finished walls. 90% of why I can't get the homeowner to scrap them and go with bb.

    On the whole waste of money....steam vs hw debate. You do not know all the facts of this job and I left them out for simplicity and it really is not pertinent to my questions. I know that there is more to afue in the real world. However with that being said....we are going from a 78% pos steam boiler....running the domestic on a hw loop and it gets air bound every now again...barely heated the second floor. New boiler is 96% with outdoor reset and we wil most likely be running a target temp of 150 on most days. With some rough math I bet we see at least a 25% reduction in cost. I did a gas 82% to this same boiler last year and this years gas costs were half....with a colder winter. However...I did not, and do not want to get into this. The new boiler has a rebate that cuts its cost in half as well. There is also no way in heck the homeowner would want another steam boiler!

    I am starting to get concerned about leaks in existing piping now with the 1/2 psi vs 15-20psi. Good point Charlie. Also good point about the hangers....i will check.

    I may pressure test all the old pipes at 30psi.

    This is my first steam conversion and i just want to make sure I have all the facts and do the best most thorough job I can. The engineer that did the heat loss for me and sized the second floor said he's converted and seen many of these convectors converted was not concerned I would have issues. The more feedback I get the less I want to do it!
  • ...they are trane!

    Injust found a barely legible trane sticker on crosse wisonsin. I posted this below as well....but how can I tell about the orifice? These appear empty looking the castings. There are 4 1/2" plugs....2 on each side square relief cut for a 3/8 drive. This is becoming a major project. I am not into drilling orifices and these are buried in the walls.....making removal the same labor as replacing.
  • Trane orific update with a bit of research (very glad I found this out now!) I have concluded that all trane convectors had orifices. I am unsure where they are located except that they are cast into them. I def. will not be converting this system to hw. The ones that have confirm that these will whistle with any amount of pumping.

    Thinking of 2 options at this point as the addition on 2nd floor is roughed for bb.

    One......I could keep the steam boiler which the homeowner hates and is the one that talked me into bb on the 2nd floor in the first place....and run a double checked bb hydronic loop of the steam boiler. There are issues with this though. I have done this in the past and it's been perfect. On this one there was an existing superstor on it. It was always getting air bound and needing to be bled and chewing up pumps. I recipes per Dan h's piping last summer....double checks...bypass....perfect. Much improved....but every now and then it still gets air bound and needs a quick simple purge. So since this...I have been apprehensive of running any hydro off steam. I know many have great success with it.

    Two. Stick to plan. Rip apart first floor convector and iron which homeowner wants gone anyway...install bb. New lochinvar, new squire indirect.

    It is not up to me to decide. I am a friend of the homeowner so it's not like a normal job. Should be...but it isn't.
  • nicholas bonham-carternicholas bonham-carter Member Posts: 6,540
    Making it work properly

    Why not simply make the steam work as it once did when first installed-quiet-efficient-even, running at 2 ounces?

    I am sure the owner's desires for a new system result from his belief that steam is -noisy-inefficient-uneven-outdated.--NBC
  • SWEISWEI Member Posts: 7,356
    steam convector

    performance falls off dramatically at lower water temps.  Check the performance curves carefully before you jump.
  • Why he's moving from steam

    A lot of valid reasons.

    Mechanical room moving location

    Existing boiler is junk. Literally

    The need to run a baseboard loop in a far away addition.

    Chimney needs a liner

    High hot water demand (6 people) needs indirect.

    Piping basement is in the every room. Nicely finished bsnt.

    On the flip side: why hot water

    Addresses all of the above concerns easily and in addition gets rid of the ancient convectors recessed in the walls with literally no insulation behind them. I ran the sq footage of the heat loss and it's equivelant to having a window open! That alone is reason enough. It makes every sense.

    To get the steam back into shape would be a lot of work, more than the new hw system. It would need a new boiler, major re pipe as it is moving, convectors added, convectors moved, far away 2nd floor heat addressed if you could even get steam there, chimney re lined. Oh...and the house was always uneven and hard to heat on cold days and the customers hate steam and want it gone.
  • Hw with bb decided upon.

    Thanks for all the input everyone.

    Without the knowledge resources on this site I may have listened to some local experts in the area and tried converting these! Boy would that stink...

    I hope others learn from this before trying to convert....trane convectors will not work with hot water systems.

    Thanks all
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