Steam coming back into boiler room

bill_105

nicholas,

just to clarify, the traps i worry about aren't 1 floor up, they are actually right at same level as the bottom of the boiler(!)

any other suggestions from the experts about ways to detect failing-open traps or other ways to try to narrow down where the problem may be that's letting steam back into the return lines?

with 83 radiators on 5 floors, and lots of pipes buried in walls and floors, it seems hard to identify the source of the problem.

should i just accept the fact there there is going to be a constant flow of steam coming back in through the return line every time the boiler reaches operating pressure?

i know that in an ideal world there would be no returning steam, but this is a case where we really don't have more money to spend and i have to figure out how much returning steam we can live with, and at what point i have to freak out and insist that the problem get solved.

bill_105

Steam coming back into boiler room

Hi everyone,

We just finished replacing every trap (about 85 of them) in our 5 story apartment building (including the F+Ts), with 2 pipe steam heat.

A major motivation was very old traps and the fact that steam was returning to the boiler room suggesting failed traps.

Well.. the work is all done and.. you guessed it.. a good stream of steam still returning to boiler room, as soon as the pressure rises to near 2psi. Enough to fog up all the windows in the boiler room. it seems to me that it's gotten worse recently.

I've tried lowering the pressuretrol but as far as i can tell i'm at the low point and going lower seems to make it hard to heat the far away radiators.

--

The question is.. is there something fixable here or should we just live with the steam returning when the boiler hits pressure.

--

One wrinkle that has me paranoid since the timing is coincidental.. and i could use some talking down from. Trying to think how to explain this without taking 10,000 words.. Recently we had the condensate pump fail on the system and the HVAC connected the mud leg connection on the boiler to the returning condensate pipe (which was a good 30" below it); essentially turning a dry return into a wet return and creating a gravity system.

well. to make a long story short, the experiment failed -- we basically pumped water into the boiler for 30 minutes and it seemed to dissapear to nowhere, as if the water was flowing OUT of the boiler into the condensate lines instead of the other way around.

so after an hour or so we disconnected everything and went back to normal, manually operating the condensate pump.

now, prior to this the boiler water was very dark and dirty and full of sediment. afterwards, to my surprise, the water in the tube to my surprise was now almost crystal clear.

that's when i started to get this sick feeling in my stomach that all the built up sediment and crud in the bottom of the boiler had now just been blown back out and up and into the old condensate return pipes. ugh.

so now i'm paranoid that we've basically filled all those ground floor traps with sediment, etc.

please talk me down and tell me i'm wrong!

nicholas bonham-carter

steamy boiler rom

how is the steam getting out of the system into the air of the boiler room?
you will probably need 3 vaporstats installed with a 0-3 psi gauge to keep that pressure down to the ideal. don't forget to rectify the lack of pigtail on the upper bank of pressuretrols.
i doubt that sediment could have been washed up 1 floor. a worse enemy of the traps is over-pressure. check the manuals that came with the new ones to see how much they can stand.--nbc

Timco

I just had this problem in SLC and the problem was a bad crossover trap (same as all the rest but straight in & straight out) that was burried in a ceiling. Time how long it takes your steam to get from boiler to where it leaves boiler room, then estimate how far it is away by how long until it gets back to boiler room. You have an open trap somewhere...

Tim

bill_105

Sorry i wasn't clear about steam coming back into boiler room. It's like this:

The return lines coming back from the entire building are the sole way for water and air to leave the system. So the return lines all come down to the floor of the basement, where they feed into a condensate pump.

Prior to the condensate pump is a big 8 ft pipe up where air can escape (in addition to an air vent in the condensate pump itself).

You can see it here:
http://mouser.dcmembers.com/boiler/Picture%20020.jpg

from what i can read in Dan's books and elsewhere, this isn't all that unusual. there are no other air vents in the system.

So in other words, the condensate return lines bring all water and air back into the boiler room.

on initial startup, you can feel the cold air rushing out of this air vent line. then after a while while steam is building, nothing comes out. but then when the system hits 2 psi or so, steam comes pouring out of the air vent. as if it's blowing through the traps, or as if there are bad traps.

bill_105

sreja

end of riser has a thermostatic trap not F+T, is this problem

While trying to track down where the steam might be getting back into the return line in the boiler, i noticed that one of the steam risers in the boiler room (actually the steam in our building feeds down from attic), is trapped with a thermostatic trap (not an F+T) as it drips into the return line.

It seems to me that all of the other return lines entering the boiler room are much cooler to the touch than this one trapped riser drip, which is burning hot, even after the trap.

So i'm wondering:

1. if this trap might have failed and that could be the cause of steam slipping back into the return line.

2. and why is there a thermostatic trap here instead of an F+T (there are 4 other F+Ts in the building) at end of main stuff lines.

3. Dan does a great job of explaining what an F+T does and how.. but i still don't really grasp why you can't just use a thermostatic trap in the place where you normally use an F+T.. Is it just durability?

Thanks in advance!

sreja

discovered some big clues today.

after checking pipe temperatures for a few days i think i narrowed down the superhot return line coming from one pipe in a wall which seemed to be superhot even when all other return lines were luke warm.

THEN,
after going into the apt. unit on the other of that wall, where the pipe may be coming from i discovered...

1) a hidden end-of-main trap that we had missed during all of our upgrading(!)
and
2) even more exciting.. a "u-turn" style end of main loop in the wall that was actually hidden inside another radiator cabinet, but one that DID NOT HAVE A TRAP(!!)

Regarding #2:
what we've discovered in this building is that on the ground floor there are many 6-8 of these trapped u-turn loops.. they look like they are end of main steam risers or drips (main steam main goes up to attic and then feeds down to units). so anyway the point is i've seen 6-8 of these u-turn loops in the ground floor units that are all trapped and i think are all steam pipes which are trapped before they return to boiler room.

so the existence of this hot looped u-turn without a trap on it makes me really think that i've found the way steam is sneaking back to the boiler when we hit 2 psi.

nicholas bonham-carter

sneaky steam

is this building ols enough, so that these u-turns could have been part of some old recognisable vapor system?if so that might be another reason to turn down the pressure as low as possible.
when i see the trouble and expense you have had with your traps, i am glad to have only one pipe to worry about!--nbc