No steam at radiator inlet, but pressure and steam at outlet steam trap

fenderman

Hi All, Just had a new commercial boiler installed and apartments at the end of the line are not getting steam (ones nearer to boiler are plenty warm!). Trunk line supplies and returns are all hot in the basement, but steam is not rising to the radiators above in 2 farthest apts. To make matters worse, one radiator has pressure and live steam at the radiator steam trap (outlet side, 2 pipe system), but is stone-cold at the inlet side and zero pressure. It's almost as though the boiler is sending steam through the returns vs. the supplies in these two apts (one above the other). Piping is basically two 4"-6" main trunks (one feeds front of the units and other feeds the back rooms), with 1.5" taps along the runs that branch to the individual radiators. All condensate returns through their own dedicated lines. I know that returns can heat up a bit due to condensate temps and some back pressure from the boiler, but this one has me stumped. BTW, everything worked fine with the old boiler until it gave up the ghost.

Jamie Hall

Let us be very very clear here. There are several kinds of distributing pipes in a steam system.

Steam mains. These are, obviously, pipes which are connected to the boiler header or to other steam mains at one end.

Dry returns. These are pipes which are NOT directly connected to the boiler header or other steam mains at either end, though they may be (often are) connected to a corresponding steam main through a crossover trap.

Wet returns. These are pipes located below the water line of the boiler, connected to steam mains or dry returns through drips.

OK.

Now. Steam mains, as the name implies, have, or should have, steam in them.

Dry returns return condensate and serve as the vent lines for air from the radiator outlets attached to them. The should never, ever have steam in them nor any pressure.

Wet returns, serve to the return condensate to the boiler.

Now having gone through all that, what do we actually have here? If the "trunk line … returns" are hot in the basement, there is something seriously wrong either with the near boiler piping or with the crossover traps or, possibly, with the level of the water line relating to the wet returns. A less likely but not unknown problem occurs if water seals are used in conjunction with crossover traps and the steam pressure is excessive and blows through the water seals.

That there is steam and pressure at the outlet side of one of the radiators (surprised it isn't more) this again suggests that something is seriously amiss with the new piping somehow allowing steam into what should be a dry return — or simply that the pressure setting on the new boiler is much too high.

Now… can you verify that the high level returns are, in fact, dry returns and not steam main extensions? And, if so, identify where and how steam is getting into them?

fenderman

Thanks Jamie. Your comments inspired me to do some reading on 2-pipe systems, esp. from Holohan. Armed and dangerous, I examined the piping system, which looks pretty conventional from the 1920's and all the diagrams I saw. Steam comes off the boiler and splits into 2 insulated mains, which run the length of the building near the basement ceiling. Running parallel to and same height as the mains are dry returns, uninsulated. At the end of the runs (farthest from boiler), the mains drop down into steam traps, as do the dry returns, and join together to drop into the wet returns, which are appx 16" off the floor (see pic). There is a similar set of drops mid-building. Radiators take off from the mains and drain into the dry returns.

I noticed some water leaking from the steam traps on the dry return drops. Upon opening the caps, water gushed almost 2' into the air. Also, the boiler site glass was completely full and the boiler wouldn't fire and was cold for at least 8 hours. I should note that the boiler recommended fill level is above the wet return piping as I expect is normal.

SO… the wet returns were full of water, maybe up into the dry returns (I didn't drain the system). There was a fair amount of head pressure in those returns, and I'm assuming, that pressure also existed in the rest of the piping, all the way back to the boiler, which was over the boiler's pressure pressure safety setting.

That all said, should/could the wet returns be that full of water (because they lie below the boiler fill level)? Why is that much water (either raw water or condensed steam or both) being thrown into the system. I'm also still scratching my head on the pressurized steam at the exit of the radiator farthest from the boiler. How is steam getting into the dry return?

Based on your detailed explanation above, I think you're on the right track with it being an installation issue, not a down-stream plumbing issue (esp. since the system worked fine in spring with the old boiler). You also mentioned the possibility of boiler pressure too high. Some of my reading indicated that in residential systems like this, 0 - 0.5 psig is preferred, and that higher pressure (2-5 psig) will actually slow steam movement, not speed it up. I did not think to check the (cold) boiler pressure before draining a bit of water from the dry return steam traps.

Big Ed_4

You have a bad trap somewhere ….

Jamie Hall

Indeed. And the first place i would look would be those crossover traps in your picture.

That is a slightly unusual arrangement — it is much more common for there to be a single crossover trap connecting the steam main to the dry return, and both dripping into the wet return. That way air from the steam main can get into the dry return and go back to the boiler. With the arrangement you have, you will need main vents on the steam mains, if they aren't already there.

Now pressure. There should be no pressure at all in the dry returns. The boiler should never run over 1.5 psi — and probably will be perfectly happy at less than 1.0 psi.

Which again goes back to those traps. They really don't like to be flooded — so how high are they set above the boiler water line?

Water level. With the boiler cold, the water level in the wet return should be exactly the same as the water level in the boiler, assuming there is nothing weird like a condensate tank.

One thing concerns me: you mention that the site glass was completely full. And as you note, the boiler water level, cold, should be somewhere in the middle third of the sight glass (usually — some boilers run higher, but never beyond the top of the sight glass). Which leads me to wonder: how much higher than that was water standing in the system when the boiler was off? And, perhaps more to the point, how did all that water get in there? It is remotely possible that the boiler is just drastically overfilled? Try bringing it down to where it belongs and firing it…

109A_5

Hello fenderman,

What changed ? A new boiler, was it properly skimmed ? Maybe it was surging and an auto water feeder was trying to maintain a normal water level, ultimately flooding the boiler and some of the system. Also there may be a bad radiator trap passing steam into the returns preceding the cold radiators.

fenderman

Positive development today. Contractor never skimmed the new boiler (Weil-McLane). Instructions specifically say to flush the boiler of manufacturing oil, potential install debris, etc. or "drastic" surges in water and pressure may occur (as noted above). Performed a flush today (and drained the system down to proper fill level) and so far, everything appears to be working as expected. Going to flush again tomorrow with some sort of additive. I had noticed brown foam in the site glass last week, which seemed unusual to me, but I didn't realize it was a symptom of a much bigger problem. Meantime, contractor is also examining all the crossover traps (I didn't measure but those traps are near the fill level). Another thing I noticed is the wet return, when it eventually meets the boiler, reduces down to 1/2" copper and joins the autofeed pipe. That 1/2" copper from the wet return pipe is a good 12" below the boiler fill line. This makes me think that there has to be some sort of head or system pressure on the wet return to force that return water into the boiler feed circuit, cuz we all know water doesn't run up hill! However, from my pics of the old system, this seems to be the old config as well. Thanks for all the help guys! Hopefully this is my last post!!!

mattmia2

what does a steam trap do way down there? if the steam can get there you have other problems.

mattmia2

The brown foam is the oil in the boiler from manufacturing and the new piping. It has to be skimmed off following the instructions in the manual, it has to be floated off the top of the water in the boiler out the skim port shown in the manual. If you try to drain it the oil will just stick to the inside of the boiler as it is draining and float on top of the new water as you fill it, the only way to remove the oil is to float it off out of the skim port.

It likely will need multiple skimmings, especially if it wasn't done when it was first fired so now all that oil is distributed through the system and will slowly work its way back to the boiler as the system runs over the next few weeks. The surging from oil in the boiler could easily trigger an auto fill valve and cause is to overfill, it will also get hot boiler water in the returns and make the returns hot. It could also be preventing some of the system from being able to vent. The steam in the return if you actually saw steam and didn't just feel it was hot it still likely a bad trap or several bad traps or a drip that is no longer below the water line.

If the installer knows anything at all about steam they would have known that the new boiler has to be skimmed.

Steamhead

@fenderman , let me get this straight- you say there are traps on the dry returns where they drop down into the wet returns?

That sounds wrong. Do the radiators have traps on their return connections?

mattmia2

Show us a radiator too. Maybe the near boiler piping although I have a feeling that is going to be wrong.

ethicalpaul

I'm a little concerned about a 1/2" wet return…

EBEBRATT-Ed

If you have no steam at the rad inlet that could be caused by the boiler being dirty and needing to be skimmed.

The same rad with pressure at the trap outlet means you have 1 or more bad traps pressurizing the return lines.

fenderman

@Steamhead - yes, see pic above. Trap on left is main and trap on right is dry return. Both drop into wet return, which you see running horizontally.

UPDATE: Boiler was flushed twice and seems to be operating well. I was wrong about the 1/2" wet return - that is the autofeed line, which joins the wet return at the Hartford loop. Also discovered an ancient condensate pump and tank in an adjoining basement, Tee'd out of and back into the wet return line (in parallel). This was abandoned when the last boiler was installed (a "midnight" job, according to the prev. property mgr), so its a wonder the system functioned at all! Weil-McLain factory reps came out and said we MAY need to install a new receiver tank and pump if we continue to experience surging and boiler flooding, but it is NOT necessarily required, and we should wait until we get into stable cold weather and let the system run for a few months.

One radiator on 2nd floor was not heating and tenant claimed water was shooting out of the air vent! Turned out it was just a stuck radiator steam trap, and the rad was full of water. Traps on these radiators are the simple "flapper" piece of metal, kind of like a mini hinge. I just unscrew the cap and jiggle the metal with my finger and the water flows. Very few occurrences.

pedmec

What boiler model number you have? I was leaning on asking if you had a condensate pump or boiler feed tank. If you have a flooded boiler all the time you might need a place to put the condensate. It all depends on the size of the system. Sometimes it takes a while for the condensate to return and before that happens the water level drops and the water feeder will feed the boiler with water. The internal volume of space in these boilers are a lot less than what we had years ago so there is a lot less water in the boiler.

fenderman

@pedmec - That's what the factory rep said (and it's what we were experiencing before the boiler flushing)! Given that the old boiler was also a Weil-McLain (perhaps 15-20 yrs old) and it functioned fine without the pump, we're hoping we'll be ok w/out it. Both the contractor and rep said don't install it unless you need it, as it is not a cheap addition. Boiler is Weil-McLain LGB-6

pedmec

well it looks like your system has been Frankensteined. how are you getting the air out of your system if your returns are below the water line. Was the old boiler and LGB-6 or was it a EGH. different water lines. Those traps need to need to tie into a return that is above the water line and have a vent, which would be the tank vent if you had a condensate pump or or boiler feed tank.

LGB-6 is a big enough steam boiler that I can't believe that you are not using either return system. the traps are an indication that you need a condensate pump. your putting out about a gallon a minute of potential condensate in the system every minute. They look like riser drips traps.

mattmia2

you still haven't told us what sort of system this is hooked to or what the pressure control on the old boiler was or figured out what the problem is that someone put a vent on a radiator instead of fixing.

Steamhead

https://forum.heatinghelp.com/discussion/comment/1820991#Comment_1820991

I'd bet the trap on the right doesn't belong there. There should not be any steam in a dry return.

The "flapper trap" on the radiators is probably a Kriebel System "baffler". This is probably a knuckleheaded Kriebel.