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Adding rooms to existing steam system

djhport Member Posts: 1

I have a 2 story turn of the century home with an existing gas steam system with radiators.  The house is only about 1400 sqft.  The second floor has two small bedrooms that never had heat run to them.  There is, however, a steam radiator in the 2nd floor bathroom.  I'd like to add steam heat to these two rooms (both about 11x12).  My questions are:

1. Should I use old style stand up radiators or some steam baseboard?  If radiators, what size?

2. How involved is this and what is cost of radiators?  Do you have to run a separate line from the boiler to each room?

3. Approx how many days labor should I budget for (assuming two plumbers per day)?

The boiler is only two years old.

Thanks for your help.


  • Jamie Hall
    Jamie Hall Member Posts: 22,928
    It can certainly be done...

    On the radiators -- I would match the type of radiator you have (not necessarily the exact style).  Radiators are rated in "EDR" -- which is a measure of their heating capacity.  One EDR is equal to 240 btu, so if you can figure the heat loss of the rooms you can figure back to the required radiator size.

    On complexity, is this one pipe steam or two?  It makes a difference in how easy it might be to pipe in the extra two rooms.  If it's one pipe, you will probably only need one pipe coming from a steam main in the basement; it might even be possible to hook into another riser on the first floor -- but watch the pipe sizes.  If it's two pipe, there will also need to be a return pipe or pipes.

    I am not in a position to comment on price -- and we don't usually talk price here anyway.

    Perhaps the biggest question, though, is -- can the boiler handle the extra load?  Steam boilers are rated -- like radiators -- in EDR.  In the case of the boiler rating, it is the total EDR of the radiators which the given boiler can handle.  So you would need to add up the EDR of each of the radiators in your house, plus the two new ones, and compare that to the EDR rating of the boiler.  If the load is just a little over, it shouldn't be a problem.  If it's a lot over, it would be a problem.

    I would very very very strongly recommend that you make sure that whoever you hire to do this job is competent at steam heat.  Some plumbers are.  Some aren't.  You can use the "Find a Pro" tab on this site to see who might be in your area who is a member of the Wall (seek by state; it works better than by zip).  And hopefully, if you mention where you are, I or someone else reading this thread will have suggestions of people we know.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Paul48
    Paul48 Member Posts: 4,469

    You can only hope they over-sized the boiler. You need to  add the total EDR of all the radiators, then check that against the size of the boiler.
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    how long is a rope, and how deep a well?

    there are so many variables here that it would be impossible to answer these questions without being in the house.

    what you can do is to determine if your boiler has the excess capacity to handle the extra load (EDR), which is likely as so many boilers were over-sized.

    the risers to these radiators will have to come up from the header, pitched correctly in the horizontal, and then straight up. the radiators will have to be sized to the rooms. you could do it all yourself, or hire a steam pro (not just any plummmer). this could be a good spring/summer project.

    alternatively, a hot water loop could work with a pump, but would need more parts than steam.--nbc
  • Steamhead
    Steamhead Member Posts: 16,728
    We've done it

    and it worked well. Of course, your boiler and mains have to support the additional load. 
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
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