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not enough heat

I had a new steam boiler installed last year, but since day one it was not heating up one radiator on the second floor. The plumber suggested that the boiler might be too small, but that there were fixes that could provide the steam needed. The first one was to reduce the 3" pipe that supplied that radiator to 1". That did not work. Since then, i have had other plumbers come to check out the problem. All said that reducing the pipe, especially from 1 1/4" to 1" back to 3" at the boiler was the wrong thing to do and when steam does make it to that radiator, it will eventually start banging. My question: is this true and is this something the orginal plumber shoud correct (recorrect)?


  • Jason Quinn
    Jason Quinn Member Posts: 96

    If you can post pictures of your system it would help; start with the boiler and near boiler piping as well as the problem radiator and its associated piping.
  • BobC
    BobC Member Posts: 5,228
    More info

    Do you know what size boiler was installed (in sq ft of steam) and how it compared to the boiler that was replaced?

    How many radiators is the boiler feeding and do you know what the EDR (surface area) of those radiators is?

    Is the piping in the cellar all insulated? If it is not than some of the heat that belongs upstairs may be warming the cellar instead.

    Has the venting of the system been looked into? What kind of main steam vents and what kind of radiator vents (assuming it's single pipe steam) does the system have? If only one radiator isn't heating the venting may not be adequate or balanced.

    Reducing that pipe down to 1" is not going to have any good outcome. Draw a simple sketch that shows the boiler, the steam main(s), and the radiator takeoffs. A simple pencil sketch will do.

    Definitely post pictures of the boiler and the piping around it as well as the non heating radiator.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • Jamie Hall
    Jamie Hall Member Posts: 17,080
    If just one radiator

    isn't heating, the problem is related to the radiator and its piping.  You don't say whether this is one pipe or two pipe.

    If it's one pipe, first thing to check is the vent on the radiator -- is it opening?

    If it's two pipe, there usually will be a trap at the outlet of the radiator.  These sometimes fail closed.  If it has, the steam feed pipe to the radiator will be hot, or at least part of it will, but the radiator won't be.

    In either one pipe or two pipe, next thing to do is to trace out the piping and make sure that there is nowhere -- nowhere -- along its length where water might get trapped.  The pipes must pitch back towards the steam main (or in two pipe, towards the return) along their full length (they can, of course, be vertical!).  While you are doing that, if the boiler is running you can trace out just how far along the steam riser you feel heat.  That may help find the problem.

    As to reducing a 3" pipe to 1" and then back up.  Ah... no.  If it works at all -- which is highly unlikely -- it will work very poorly indeed.  More likely, if it really does go back up in diameter, it won't work at all, and you will find that you have heat up to that point -- and no further.  Saturated steam is funny stuff that way.  You can reduce down (making sure there is nowhere for condensate to be trapped) but you can never increase in the piping (you can increase in the headers at the boiler itself, but that's a different story).
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • bostonsh
    bostonsh Member Posts: 3
    not enough heat, picture included

    I posted earlier about not getting enough heat to one radiator. Here is a pic of the connection in question: 3" elbow to a 1" slanted pipe to a 1 1/4" vertical pipe to the radiator on the second floor. Does this look right?
  • Jamie Hall
    Jamie Hall Member Posts: 17,080
    Why oh why

    do folks do these things?  And it looks as though it's been there for a while, too...

    Well, first it's not as bad as I thought it might be... and it might work, maybe.  As I look at the picture, though, it looks as though that 1" goes up at about 45, then 45s over more or less level, then 90s to the right, still more or less level, then I take it it 90s up in the 1 1/4?  If that's correct, there is a spot there where a good bit of condensate could be trapped (in the vicinity of that 90 to the right or at the base of the 1 1/4) which could choke off the flow of steam to that radiator quite effectively; oddly enough, it might not hammer.  Check the pitch of those almost horizontal sections -- they should slope, quite decidedly, back to the main.  It would be much better if they were larger -- don't have to be 3" to handle one radiator, but I'd want 1 1/4 or 1 1/2...

    You will want to insulate that steam main as soon as you can, too -- that will help.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • bostonsh
    bostonsh Member Posts: 3
    why why o why?

    Thanks for your post. The elbow has actually been reused. The work was done last year. The pitches are all good towards the main. I had another guy come by to check out the problem and he increased the pressure in the boiler a bit. Since then, everything has worked perfectly. He said that this connection thou might start to bang after a while. I guess i want to confirm this possibility before it happens as i don;t live in the house. What is the likelihood that it will bang and should i replace it with a 1 1/4" pipe?
  • Jamie Hall
    Jamie Hall Member Posts: 17,080
    If all the pitches

    really are good, it shouldn't bang as the condensate will go right back to the main and that drip I see there (of course, being steam, now it will bang just because I said it wouldn't...).  It would be better with 1 1/4, but if it's working now...

    May I ask what the pressure was increased to?  If it's over two pounds, that's not good -- it will hurt the vents (as well as costing money).  However, sometimes one does have to compromise.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • gerry gill
    gerry gill Member Posts: 3,010
    as a general rule,

    the horizontal pipe is at a minimum one pipe size larger than the vertical pipe on steam work..sometimes more than one size larger, but always at least one size larger.
    Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

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