Two-Pipe, Air-Vent Steam Heating

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Two-Pipe, Air-Vent Steam Heating

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PeterC_2

Thank you for the article. I just purchased a 100 year old house with steam heat and read your book "we got steam heat". I could not figure out what kind a radiator's / system I had. Now I know. 90% of the radiators in the house match the image above exactly (two pipes at the bottom with air vents). The other few are one pipe units with air vents. I had a couple of questions though.

The pressure on the outside of the pressuretrol was set to about 8psi. A pressure gauge next to it was bottomed out while the furnace was running but I turned the pressure down to .5 psi as you recommend in your book. The differential pressure was /is set to 1psi.

- Is it true that I can shut these two pipe radiators off if they are two hot? Do I shut off the supply, the return or both?
- Can I half close a valve to reduce the heat from the radiator?
- The upstairs of the house tends to get too warm but I don't know if thermostatic radiator valves would be a solution.
- As per your book I also looked for main steam vents in the basement and could not find any.
- While only in October the house seems to be heating fine, despite no insulation on the mains in the basement and no main air vents.
- Should I really get main air vents if the system seems to be working? A new boiler was installed about 4 years ago before I bought the place and the previous owners had a low utility bill for gas and electric of $145 a month averaged over the year despite living in cold windy oswego NY. House is a well insulated 2700 sq feet.

DanHolohan

Yes, you can shut them off if the room is too hot. Shut both valves. Supply valve first.

Yes, you can throttle the supply valves on this system

If you use TRVs, use the type that goes between the air vent and the radiator, not the type that replaces a supply valve. Think of this as one-pipe steam with drains.

There may not be main vents on this system. It's that old. Main vents will always make the steam move faster, but you should balance the cost of those (including installation) against what you have now.

If it's heating, that's great!

ColumbineCottage

New to steam heat and this article helped identify my system-to a point. My house had steam heat installed about 1910 and I would guess it was done in stages. Some radiators are 2 pipe with vents and some are 2 pipe with traps. Not all radiators heat the same or at all. I know there is some issues I have thanks to reading "We Have Steam Heat" but my question is can these radiators coexist with some having traps and some using vents? I would assume they did at some point, but it's never safe to assume.

Jamie Hall

Oh help. Well, I'm going to have to go on theory here, not practice, so take what I say with a grain of salt... I would say that yes, they could -- provided that the return valves on the two pipe/air vent radiators were closed, and the radiators repitched to allow condensate to drain back out of the inlet.

@Steamhead ? Help?

DanHolohan

The radiators without steam traps may have orifices in the inlet valves, or considering the system age, there may be an orifice in the outlet. Photos would help.

Thanks for reading me!

ColumbineCottage

Well let me add one the proverbial "wrench" to that. None of the radiators have shut off valves on return side-only on the inlet side.

ColumbineCottage

I will try and get photos tonight and post them.

DanHolohan

Close-up pics of the supply valve and the return fitting will help. Thanks.

Jamie Hall

ColumbineCottage said:

Well let me add one the proverbial "wrench" to that. None of the radiators have shut off valves on return side-only on the inlet side.

Ooops. Well, we surely will need photos then -- including close ups of the return side fittings.

EBEBRATT-Ed

Could be that his 2 pipe radiators with no traps are dripped into a wet return and they should work fine with an air vent on the radiator

DanHolohan

Good point, Ed. Thanks.

EBEBRATT-Ed

@Dan Holohan Thank you!

I learned most of what I know about steam from you!

DanHolohan

Ah, shucks!

Jamie Hall

EBEBRATT-Ed said:

@Dan Holohan Thank you!

I learned most of what I know about steam from you!

me too.

Mad Dog_2

Dan is da man! He came along at the right time for me too! Ha ha. Ive seen lots of these systems in Old Manhattan and City of Brooklyn
Buildings. Mad Dog

mikeg2015

Wasn’t there a type of vapor system with no traps but with orifices on the inlets with the radiators oversized so steam fully condensed before it reached the end of the radiator. These probably of course had vacuum vents. One advantage of as more radiator mass means more even heating with lower cycle rate.... or more importantly probably less frequent stoking of the coal boiler.

2nd advantage as well, is if pitched to the return pipe you might have slightly higher boiler efficiency due to lower return condensate temps. Also wondered if You could have a “economizer” radiator somewhere nearest the boiler like a kitchen or foyer and you would allow gravity pressure differential and send it all the return condensate passively. Could use a 3 way valve to regulate temp.

I’ve also always wondered if I could size my steam boiler just above building heat loss and then carefully balance it with very very slow air vents on the radiators.

ColumbineCottage

Here are the requested photos for my "hybrid" system. As you can see it is a mix of traps, vents, and even both! My concern is that they all will play nice together. Some radiators heat wonderfully while others not at all. I know there are items that need to be repaired such as replacing main vent, lowering system pressure, rebuilding traps, and a few other items. I am assuming this system all worked at one time, but you can never be sure. I just hate to be chasing my tail and replacing parts if it will never work properly and since I have no reputable steam contractors in my area I will need to learn as I go. This has been a highly valuable resource and thanks to all in advance who offer some sage advice!

The following 3 pictures are of a great working radiator







The next two photos are of a radiator that only works when house temp is above 72 degrees.





The next 2 photos are of a radiator that never gets hot although both pipes are hot.





This last photo is of a great working radiator but has 2 pipes, a trap, and a vent!

EBEBRATT-Ed

We would need to see basement piping supply and return to different radiators. The first radiator (the one that works) has a CRANE elbow on the return that looks suspicious. I don't know if Crane made a vapor system with a orfice in the elbow

nicholas bonham-carter

If steam gets into the returns, the traps feeding into that line may close without any steam in the radiator.
Maybe you can test them by closing all the valves, and firing the boiler. Next, open one valve after another singly, while feeling for steam leaking past a bad trap into the return.
Turn the air vent upside down on the working rad, and you may find it does not heat.
The trap less rads probably have orifices in the inlet to limit the steam to that which can be condensed by 80% of the rad.—NBC

JUGHNE

Dan, I too must thank you for getting me into the world of steam!

A question concerning the building in the story.
Is there a wet return below each floor that the return pipes drop into? With 15 stories that would be a lot of pipes running down to the basement.

Just to have condensate drop down a vertical pipe 15 stories is hard to imagine.
I envision some sort of "switchback" for the DWV system and maybe the condensate also??

DanHolohan

Thanks. With a building of that size, it would have been set up like a ladder, where the steam favored the supply riser first, and then passed into the return riser as counterflow to the steam as it approached the radiators. A classic two-pipe, air-vent system.

Malcolm

Hi Dan, Like the others above, I learned a ton about steam from you and one of your books. We spoke a few years ago about the issue of running the system at 1-2 psi which I have been relatively successful at doing. My current frustration is over the consumption of components in the return side, just had a pinhole in a return pipe pointed out to me a minute ago. It has been occurring to me that some of this could be reduced if I remove all the traps and just put one big bucket trap next to the condensate return barrels. Then all the piping would be full of steam and therefore mostly dry. Sounds like this would work? A complication is that half the system drains into a remote return tank 200' away from the boiler room where it is pumped up high to get slope enough to drain back. That loop is where the pin holing is occurring and I was thinking that when these return pipes are replaced in the next week or two, I would have the end where it drops into the main building return changed to an inverted U so that pipe only drops water into the returns when the pump runs at the other end of that branch. I'm thinking the return pipes will last longer if they are flooded and there is no oxygen over the liquid? Sorry about two questions but that's were I am - can't get the system down to one question! Malcolm Black at the Beaumont Mill, Glen Williams Ontario Canada

DanHolohan

The traps are there to keep the steam out of the wet returns, and I know you get that. If you turn wet returns into steam lines you're probably going to have a lot of water hammer.

Pumpguy

@Malcolm,

The concept you offer is called "Master Trapping", one big trap at the end of the return instead of all of the traps out in the system.


The problem with this idea is, now you have the same pressure in the returns as you do in the mains, and with no difference in pressure, you have no flow, and when you have no flow, you have no heat.

Remember, "All fluids flow from high pressure to low pressure, ALWAYS"

Malcolm

Hi Pumpguy, now I'm confused by Dan's comment above or elsewhere about systems built before the invention of traps where the movement was caused by the differential in piping size "steam takes route of least resistance" or something like that. Seems tome that if you remove heat from rads and unit heaters there will be condensation which reduces the volume in the unit by 177 %. The condensate would still run through the return pipes for mechanical reasons. I see the issue of steam being over the condensate as it runs which must have been the case in the systems described by Dan?
My system has that structure already, the steam headers are 3" and 4" with returns at the traps 3/4 or 1" dropping into 1 1/2" in one loop and dropping into 2" in the other loop. I was thinking that I wouldn't even need a trap at the tank, just put an upright elbow at the outflow in the tank so steam can't get into the tank itself. In theory once up to temp, all lines would be dry even above the condensate running, except when it gets to the tank. If the tank steams up then add a trap. The loop that goes to my residence has one air vent in the farthest rad but in spite of header size this rad is very slow to heat up. I replaced the trap element yesterday but it didn't make much difference. It's only 100' of pipe max from boiler. bloody mysterious.

Pumpguy

@Malcom,

My comment above was only confined to the installation of a "Master Trap" just upstream of a condensate return pump.

The subject of installing a "Master Trap" is covered in Dan's THE LOST ART OF STEAM HEATING on pages 31, 163, 174, 182, and 187.

Dan's comment is confirmed on page 31. At no place in this book or any other authoritative literature I have ever seen is such an arrangement recommended or even suggested.

Please understand that as my handle suggests, I'm a pump guy and only see steam heating systems that have pumps on them.

That said, I've learned a lot about steam heating systems over the years, and feel qualified to comment on many piping arrangements I see. I will also say that I also know there many piping arrangements that may be correct but I couldn't say for sure one way or the other. As a result, I try to keep my comments confined to what I know, offer suggestions that may be helpful, and am not afraid to admit that I don't know when that is indeed the case.

Hopefully others here on this board with the necessary knowledge and experience will reply to your post.

EBEBRATT-Ed

@Malcolm It's unfortunate to have leaks and trap repairs but there's not much you can do except fix it. It will never work properly otherwise.

Master traps cause all kinds of issues. I would suggest Dan's book LAOSH. It explains most everything

Malcolm

Hi Guys, I really appreciate the time you take to try and help - I think it's amazing. I checked p31 of Dan's book and read what he had to say about master Trapping. Damn. The notion of having all the pipes in steam and therefore dry seemed to be the obvious answer to corrosion which is one of my big issues. Boiler water is testing 7000 micro-Siemens conductivity which is not good and I don't really know what to do about that.
I have another problem which comes and goes, the rad at the end of my residential loop won't steam up. It's on the second floor, feed pipe is under it. Steam pipe is hot to 6" above the second floor. Even if I unscrew the vent and remove it - the steam will not rise. It can't be a return blockage if the vent is removed, the rads 10' away and further are working perfectly. The steam header is 3" to within 4' of the rad then steps down to 3/4 with several elbows to get over a beam and up to the rad. Header is pitched rising toward rad. I jacked pressure up at boiler in stages today, first to 1 1/2 psi then to 2 psi. Nothing changes - another heater began to work in a different loop however.

Malcolm

Few updates. I raised cut out pressure to 2 1/2 psi and steam is now getting to every device and it's been warm. I used a digital thermometer I got for testing old marine engines and after re-reading Dan's book a bit found I could identify a dead trap in seconds - wonderful - need to buy another batch however. So it's working now but not at low pressure.

JohnNY

Just to share....

I'm working on a building now that was built, I'm told, in 1888. The radiators say "AA Griffing NY PAT Sept 22 1874"
This was a 2-pipe air vent system that began to develop problems at some point. The building hired an engineer that added ½" traps to every radiator and the building banged like crazy. So they hired another engineer that replaced the ½" traps with ¾" traps, and added a condensate pump, and I'm told the building saw great improvement in the noise.
Now they're trying to get rid of the noises that remain, and a few new ones.
I want to tell them to restore the system and get rid of the traps (12 stories of apartments) and pump, but I don't think that's going to happen no matter how well I explain it so I'll have some alternative Band-aid fixes at the ready because that's just how life is sometimes. Again, the building's system is not working terribly. In fact it's not very far off from working acceptably well. But there are new tenants, they happen to be Rockefellers, and they want it as close to 100% as it can be.
I'm paid as a consultant and I don't need to sell any work but I need to submit a very clear report detailing what's gone wrong here. It's going to be interesting.
Yes. I name dropped.

dopey27177

JohnyNY

I retired early from my consulting work because I faced the same bull that engineers who know nothing about old or even new steam systems. They graduate from college get a job and some with master degrees never used a Hoffman Engineering Manual, a Dunham Bush Pocket Manual or read any other manual that should be in their library.

I received calls from many of my old customers to see what was wrong with the engineered upgraded systems. After a review of these systems and providing a price for my consultant fee I was told that they they could not sell that to the board because the board would be in a hard place as the work that was done did not save sufficient fuel or cure the failure to do proper maintenance on the boiler plant and heating system.

My visit to the sites was a waste of my time as to get paid for that time was a freebee because providing a proposal still would not get me a Job.

My proposal always had a guaranteed result and if not met they did not have to pay me.

When customers show no loyalty to the consultant of record and use engineers to redesign old heating systems I found it was time for me to hang up my shingle.

Jake

Jamie Hall

I hung up my shingle (Registered Professional Engineer -- several specialties) a couple of decades ago, @dopey27177 , for one very simple reason: the errors and omissions insurance premium had reached the point where I couldn't charge enough to cover it, never mind buy lunch. And I'd never had a claim of any kind (a few complaints, rectified, but not claims).

There is a vast gulf between many of the younger engineers and, dare I say it, tradespeople we are seeing now and the ones who were coming along when most of the folks who contribute to Wall were coming along: they lack two things. Basic fundamental science and on-the-job training, sometimes for years, before collecting that shingle. I'm not quite sure what to do about the fundamental science part (well, I have some ideas, but they are hardly PC, so not here, not now) but the on-the-job training is a different matter. In the trades, this still is the classic apprentice -- journeyman -- master route, but finding people who are willing to be apprentices seems to be getting harder and harder. When I go my PE license (don't ask, but it was a long time ago) you still needed at least 6 years of field experience even with a degree, and 12 if you didn't have one. Not any more. You also needed to show continuing field experience to keep your license. Now? As @dopey27177 notes up there, you can come in with a satchelful of manuals and a Masters and off you go. Perhaps worse, you don't need to be active in the field to keep it -- a few Continuing Education course credits every year and you're fine.

Funny story: when I finally did go and sit my PE exam -- 6 hours worth -- I arrived at the exam site with a slide rule and three manuals I thought would be useful (they were). I looked at the crowd around me -- all of whom were at least a decade or more younger than I -- with their suitcases of manuals and handbooks (plural, and suitcases, literally) and fancy pocket calculators and figured I'd had it, but it was a nice drive anyway and a day out of the mud... I passed...

JohnNY

Consulting on work I know I'm not going to be hired to do has been a real learning experience for me. I like it. It gives me a glimpse into what it must be like to be a PE and not have to consider how something will physically get done. How liberating.
What sets me apart from my Consulting Engineer friends is my consideration for the limitations that field conditions are likely to present to the guys actually swinging the wrenches. Well, that and other stuff. Like 35+ years in the field. At 52 with a head full of grey hair now, I look like one of the more experienced people in the room without having to open my mouth. Still, I get challenged often, mostly by Building Supers who I've learned long ago never to underestimate. Some of these guys really know their systems even if they don't use the right technical terms for their functions. So I hear them out, respectfully, and we always and without exception work together toward the common goal with great success.
My Errors & Omissions policy is pretty resonable so far. It's been interesting...

Jamie Hall

I've learned more about engineering over the years, @JohnNY , from the guys and gals swinging the wrenches (or whatever -- I had a young lady assistant once who could pick up a manhole cover and walk away with it...) than I ever have from book learning. But I was always willing and wanted to work with the crews, not supervise them, which made it easy to do.

dopey27177

Dopey to Jamie Hall

Gotcha. I admire men that got their PE's the hard way.

I can not compare my knowledge to yours because each consulting job I worked on I spent a lot of time in my library trying to find economical ways to restore systems without rip outs.

I worked as an installer and repair man in this industry as well as a supervisor, I learned if a man designed and install it and worked from the get go and if man built man can fix it.

Jake