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mystery steam

i installed a burnham mega steam boiler wusing the drop down header design which i love. here is the problem. the house has 9 convector element style radiators set in the wall. the house is split into 2 halves side A and side B. both loops are pretty much exactly a mirror image of each other except side A has 4 radiators and side B has 5. boiler heats up starts to make steam and the steam travels into header and up riser to 2 - 3" tees( 1 for side A and 1 for side B) the steam will get to those tees equally and then the problem starts. side A will allow the steam to travel into tee up a 3" x 12" riser and travel around basement and back in about 30 seconds to a minute, side B will take about 20 minutes to travel 10 ft to 2nd radiator, then it will start to move but no where as fast as side A. every radiator has new adjustable steam vents, as well as 2 new #35 main steam vents. i closed side A vents completely off and that side still continues to heat those radiators fast and hot. i then took the main steam vent on side A out and plugged to see if that would help and it did not, i then removed evry radiator vent and  main vent and it still did not make a difference. radiators still did not heat up quickly and the return pipe still did not get real hot for a long time. by the time side B heats up the thermostat shuts down and the 2nd floor radiators are cold. there is a bathroom radiator right above boiler not even 3 ft above 3" tee and riser i took the vent right off and you can hear the vapor like pulsating but even with .5 to 1 psi in boiler it still did not come out quickly or heat up radiator completly. i am sort of at a loss. not sure if ihave aplugged wet leg, or too much steam pressure. my riser from drop down header is a 2" black steel. not sure why the steam gets to the 2 tees at same time but then just stops for 1 side and cranks throug the other. any direction would be so appreciated.


  • one side plugged?

    i think your description of :"and you can hear the vapor like pulsating" would suggest  water in a low spot, trapping the air in front of the steam, in that line. 

    this would be a good use for an ir camera to show how far the steam gets in the pipe. to check for an obstruction [which is unlikely, but possible]  can you connect a hose to the farthest radiator vent tapping and back-flush the return? it would be best to wait until the boiler is cold as some water will make it to the boiler.

    to check for a sag, i have put tape on the pipes, with arrows marking the direction of slope using a level. if you see 2 arrows pointing to each other, you have found the problem!--nbc
  • Paul Fredricks_3
    Paul Fredricks_3 Member Posts: 1,557

    Sounds to me like panting. Are the mains insulated?
  • heating101
    heating101 Member Posts: 4

    they were, but they are in the process of reinstalling insullation. had asbestos. the only concern is the two halves are almost exactly identicle and yet the other side has no issue at all. pipes are pitching good. not a very long run, whole loop probably 50 ft total linear.
  • Paul Fredricks_3
    Paul Fredricks_3 Member Posts: 1,557
    see what happens

    after the insulation is on and go from there.
  • Jamie Hall
    Jamie Hall Member Posts: 19,907
    You say "almost identical"

    but... one question which occurs: is there any sort of restriction in side B somewhere? By which I mean a place -- even a very short place (like a valve) -- where the pipe size drops and then expands again? That will kill steam movement beyond it, as the steam will condense where it expands. Sounds counterintuitive, but low pressure saturated steam is strange stuff.

    Also, if side B isn't insulated and side A is, that could do it.

    I note that if you have indeed plugged every way that air can get out of side A, then the radiators on that side shouldn't heat -- the air has to go somewhere, and if you've managed to plug every possibility...

    When the boiler starts up, spend a little time and see just how far down side B steam is moving and how fast (you can use the ouch test for this).

    To go back to almost identical -- clearly they aren't, or they would behave the same. Find and document the difference(s). There may be something there...

    I know it sounds obvious, but did this start after you put in the new boiler? If it was working before, but isn't now, that kind of narrows down the possibilities...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • heating101
    heating101 Member Posts: 4
    identical sides

    i didnt plug the sides i just shut down the steam vents so im sure some air will still get out, i did the ouch test and it really just slowly trickles along even when i took all vents out and everything was wide open. logic tells me that  i have a blockage but if the return at the boiler was plugged then when i removed the vents i should have been able to make it work. there is insulation on both sides in spots and not in others. the pipes have same pitch no bows or dips, there are no reducers or valves. not sure if the style radiators i have make a difference, there is a pipe on the bottom and top with a chunck of cast iron like a pin boiler in between. like i said the two sides are exactly a like. as far as was it like this before, of course they say no, though they did say at time of install that those radiators had problem heating up but not as drastically. i think my next step is to remove some piping and try to look for blockage
  • jpf321
    jpf321 Member Posts: 1,568
    pics please

    please post some near boiler piping pictures .. the other day someone had a problem with 1 side not heating and it turned out to be a near-boiler issue. 
    1-pipe Homeowner - Queens, NYC

    NEW: SlantFin Intrepid TR-30 + Tankless + Riello 40-F5 @ 0.85gph | OLD: Fitzgibbons 402 boiler + Beckett "SR" Oil Gun @ 1.75gph

    installed: 0-20oz/si gauge | vaporstat | hour-meter | gortons on all rads | 1pc G#2 + 1pc G#1 on each of 2 mains

    Connected EDR load: 371 sf venting load: 2.95cfm vent capacity: 4.62cfm
    my NEW system pics | my OLD system pics
  • Paul Fredricks_3
    Paul Fredricks_3 Member Posts: 1,557
    Do this

    Take out a radiator vent and hols a piece of tissue over the hole. With the thermostat calling and the boiler making steam, watch the tissue to see what the air in the radiator is doing. Air should blow out the whole time, but if it blows out, then sucks in, over and over, it's panting. That's because the steam is collapsing as it hits a cold section of pipe. And that's due to no insulation.
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