Steam and positive pressure in dry return line

Johncapn

Hi All.

I am troubleshooting our steam heat system. 2 pipe system with a couple of radiators on the end of a steam main heating slowly. no vents were installed at the end of steam mains, and never seemed to have ever been. We just replaced the F&T traps. I tried to add vents to the end of the dry returned and we get spluttering of (lots of) water out of the Gorton #2's I opened the upper dry returns and got Steam in there!

Can anyone suggest what may be going on! I am removing all steam trap bodies and inspecting them at the moment?

3 story building, 1936 vintage with Barnes and Jones steam traps, and valves.

Thanks!

Jamie Hall

If you have steam in the dry returns, you have at least one bad trap (it only takes one, though where there is one it is likely that there are more!). Or -- not unheard of -- a pair dripse, one from a dry return to a wet return and one from a steam main to the wet return -- where the wet return isn't, due to a replacement boiler being installed with the water level too low. This is not, unfortunately, all that unusual... but not hard to diagnose (it's harder to fix) by tracing out and checking the actual level of any wet returns.

While you are pursuing failed traps (they are usually not that hard to find -- the outlet may be good and warm, but never steam hot) make sure your pressure is low enough -- cutout not over 1.5 psi.

Johncapn

Hi. Thanks for the reply. What is "a pair dripse"?

Jamie Hall

sorry. My typing lately has had problems... it should have been "a pair of drips" -- that is to say two vertical lines which carry condensate down -- one from the steam main and one from the dry return -- down to the wet return. Not all systems have them. The thing is that they had to go to a wet return -- there has to be a water seal at the bottom so that steam can't zip down the one from the steam main and right back up the other one into the dry return.

Johncapn

Hi Jamie. So heres what I found.
1. On the first floor of the building there were two steam traps that had no cage units in them! they were in lines that ran from the steam main back to the dry return, bypassing the radiators - is this the drip lines you mentioned?
2. the third floor rental unit bedroom,which is the radiator furthest away from the boiler had a different steam trap to the rest of the 40 or so radiators in the system, a hoffman 8c 3/4 inch. The remaining steam traps in the building are Barnes and Jones 12's. This trap had the incorrect cage unit in it ( it was one for all the other steam traps). I have ordered the correct barnes and Jones cage unit for this trap. Going forward I might replace the Hoffman trap with a B&J but thats a summer job as I would have to extract the 3/4" radiator outlet and put in a 1/2' and I know that is not going to be easy!

I have still some steam traps to check but it will have to wait until Monday. I have been able to reduce the steam pressure in the system from 1.5lbs to 12oz and still get heat to the furthest radiator on the steam main.

I wonder if the following problem is related, I have a 0-3 psi gage on my boiler and well as the 0-15 PSI. Both gages (on the same pigtail Flicker (about a 4-8 oz range) a lot as if there is a lot of pressure fluctuations in the system. Is there a way of "smoothing" this pressure out?

Steamhead

1- No. These are "crossover traps" which allow the air in the steam main to be vented into the dry return. I bet when you install cage units in these, your dry returns won't have steam in them- or if they still do, it will be much less.

2- if that radiator is very large, it might really need a 3/4" trap. I'd simply rebuild the 8C.

The flickering gauge might be due to dirty boiler water.

Jamie Hall

Steamhead said:

1- No. These are "crossover traps" which allow the air in the steam main to be vented into the dry return. I bet when you install cage units in these, your dry returns won't have steam in them- or if they still do, it will be much less.

2- if that radiator is very large, it might really need a 3/4" trap. I'd simply rebuild the 8C.

The flickering gauge might be due to dirty boiler water.

Kind of thought there might be a crossover trap or two hiding in the weeds somewhere... but not having a cage in them would explain a lot! (except... where did the cage go and why? ... all together now... )

Johncapn

Thanks for the reply Steamhead. If I understand correctly, these crossover traps explain why the end of the steam mains do not have any vents on them and appear to have never had ( they terminate in inhabited space)? All venting is thus done at the end of the dry return? It will not surprise the group that the same plumber who missed putting the cage units in the crossover traps also did not vent the ends of the dry returns....
I am working on that also...
Don't get me started on how he set up the boiler...

Johncapn

I have spare cage units on hand for the traps and they are already installed in the crossover traps, I was immediately able to dial the pressure back on my vaporstat to 12oz and get heat around the building. I will open up the dry return again today and inspect the contents!
At the end of the lower, first floor dry return I had added 3 Gorton #2's and a Hoffman 75 to just before it drops down to the wet return. The height of the dry return above the water level in the boiler is about 14 inches. Having steam pressure in the dry return line would explain why water was coming out the vents in the Gortons? Dialing back the steam pressure in the system would also help?
I have a dry return back to the boiler room that services the 2nd and third floor of the building, it is at the ceiling height of the first floor and has no vents... The plumber who replaced our boiler 2 years ago must have put our system back together and omitted them, no? There is a tee which he blanked off that looks like I could put some vents on, but it is not quite at the end of the dry return. Should I try a Gorton vent on this If there is now no steam pressure in this dry return?

Greening Steam is on my desk as I type this!

Johncapn

Soooo. I removed the cap on the 1" connection on our 2nd and third floor dry return line near the drop down to the wet return. On running the boiler I had a nice, steady long fire of the gas burner maintaining a smooth-ish 6-8oz of pressure in the system. I could feel a gentle "exhale" of cool air at the now open "Tee". All radiators were became hot all the way across, even the last two in the system, I could see steam coming out of the radiators when I opened the traps! on closing the cap on the tee in the dry return the needles on my pressure gages started "bouncing" and pressure spiked to 16oz, cycling the gas burner on and off. Does this appear that I may have "fixed" my steam system if I put say 3 Gorton #2's at this point in my dry return?

Jamie Hall

Amazing! Sounds like you're good to go with those vents added...

Johncapn

Can someone point me in the right direction for the calculation for the number of Gorton #2 vents I should put in? The steam line is 5" for 25' from the boiler including the riser and header, then splits to 2, 4" lines at 90' each. Dry returns are 2" pipe.

KC_Jones

Well the OP states they had a 1" pipe open and a 1" pipe would be equivalent to 5 Gorton #2 vents. I am not saying it's enough, but unless they add more connection on the returns they can't vent any faster than the 1" pipe that is available. I do agree though this would probably be a good case to explore alternatives given the size of the system. I know some of the pros have used other solutions for massive venting situations like this.

Fred

This may be a case where A steam Pro should be on-site to look at what this system really is. It is hard for me to believe it has run for 80 years with no venting and no signs there ever was any venting and now we feel it needs all kinds of vents on the Mains. Is this some type of Vacuum system?
Just doesn't feel right to me.

Johncapn

This was a former City of Boston Building. It was abandoned for 24 years when we purchased it and renovated it. The plumber who replaced the oil fired boiler really messed up the near boiler piping but did not mess with the radiators or steam mains. However when we purchased the building the City had installed ancillary electric baseboard heating in many of the rooms on the third floor and second floor, evidence that the building had not been heating right for a long while.

The ends of the dry returns had been altered by the plumber. It is very reasonable to suspect that he removed the venting on the dry returns and capped them as there was a spot to put a vent on the end of the first floor dry return with a 1/2" take off. Until I got the pressure down to 8oz this would flood ( having just re-read chapter 7 in "greening steam", "greening the traps" I note that the Building appears like the drawing on page 158 describing a two pipe gravity return system and that the "B" dimension between the waterline and the end of the dry return is about 14 inches. This suggests that maximum operating pressure of the building should be no more than 8oz, no?). The second and third floor dry return had a capped off 1" outlet

The ends of the steam mains are in offices. if Gorton #2's were in there or some older form of vent they would have exhausted moist air into those rooms?

Or, in a properly maintained system could Gorton #2's function in a finished space?

Were the crossover traps an alternative to "massive venting" I note that each of my Barnes and jones crossover traps have a greater vent capacity than a Gorton #2 and we have 13 of these (35.1 CFM @ 3oz) Therefore the venting could occur at the ends of the dry returns perhaps? The only problem I see with this is that at the end of the steam main you loose most of the crossover trap venting, which would explain some of the difficulty getting steam to the third floor radiators at the end of one of the mains.

Thank you to all that are reading this thread and helping me to untangle the situation. I believe I am close to a solution and owning a great, economical system.

Jamie Hall

In my humble opinion... and despite the general comment that there is no such thing as over venting mains and returns...

Put in enough #2s at the boiler ends of the dry returns to match the capacity of the crossover traps feeding the returns. Will the pressure running be at one or two ounces? No. It may even be as much as half a pound. DON'T put them at the ends of the steam mains. Let the crossover traps do their job.

That venting will be similar in capacity to the crossover traps. There is no point in exceeding the capacity of those crossovers.

Fred

It makes me feel a lot more comfortable that you have found indications of where vents may have been. Yes the crossover trap does act like vents for the Mains but there is still a requirement for vents at the end of the dry returns. The question is "how much" I know Jamie Hall has a relatively small nunber of vents on his dry returns but I don't know how long his Mains/returns are. Maybe he will jump back in on this thread.

Steamhead

So each of those 4", 90' mains is vented by a crossover trap into the dry return? Are they 1/2" traps?

Johncapn

Hi Steamhead.
Yes they are. Barnes and Jones 1/2" traps, 13 of them.

Steamhead

But only one 1/2" crossover trap at the end of each steam main, correct?

Johncapn

Yes

Steamhead said:

But only one 1/2" crossover trap at the end of each steam main, correct?

Yes, correct

Steamhead

With mains that size, you want to use Nicholson A33HC crossover traps. These have 1/2" orifices in them, and will out-vent every other 1/2" trap I've ever seen. I've attached an excerpt from the Nicholson catalog showing their thermostatic traps- the specs are on page 2 of the .pdf file.

These traps are not cheap- they run about four times as much as a Hoffman 17C or Barnes & Jones 122A. Also, they do not have built-in unions so you'll have to pipe in a union somewhere. And they often take a while to get. But after having used one on a lopsided Webster system and seeing what it can do, we plan on stocking a couple- also a couple 3/4" A43HC units.

And we'll post some pics soon, of the new boiler we installed there as well as the trap.

nicholas bonham-carter

If all of your radiator, and crossover traps are working, then maybe there is no need for any main air vents.--NBC

Johncapn

Steamhead said:

But only one 1/2" crossover trap at the end of each steam main, correct?

Hi Steamhead and fellow "Wallees" i forgot to mention that at the end of the steam main are two F&T traps, new this year to replace the original Barnes and Jones units. One on each end of the main. Sorry. I know that changes the mental picture that you have of our system...

Steamhead

Do the F&T traps discharge into the dry return, or wet return, or both?

Jamie Hall

For Fred -- there are three 3" steam mains, each about 50 feet long, give or take. And yes, the system would work at lower pressure with more vents and the Nicholson crossovers which Steamhead mentioned -- but it runs at about 3 ounces now as is, so... if it ain't broke, don't fix it.

Johncapn

Steamhead said:

Do the F&T traps discharge into the dry return, or wet return, or both?

Dry returns

Johncapn

Johncapn said:

Steamhead said:

Do the F&T traps discharge into the dry return, or wet return, or both?

Dry returns

I have been reading and studying our system. Here is a thought. the new F&T traps that were installed are different dimensions to the old B&J F&T traps. the outlet for these runs "uphill" about 2" before dropping down to the dry returns. would this put back pressure on the system and account for the fluctuations in my pressure gages?

I would attach pictures but I don't seem to be able to get it to work...

Johncapn

OK I think I have attached the photos correctly. Here are the two new F&T traps that were installed. Now I know more, it seems to me that the "uphill" exits from the drain side will cause a minor airlock that will cause pressure fluctuations and not allow air to clear the sram vents efficiently. I will start a new post about this too. Any comments would be appreciated.