Assessing a Two-Pipe Steam System

Brad White_171 · May 2007

The B dimension is, surprisingly... 56 inches. I have a suspicion to be confirmed that Ed Wallace might have done this install some years ago.

The devices seemed like a vent (air eliminator by another name would not smell anything like a rose). I suspect that it might be a Hoffman Receiver Vent as depicted in Figure 56 (Page 266) of The Lost Art. I will have to look at it with regard to the peripheral piping. Some more detail would help, maybe a new set of eyes. I will stroll the library too.

Does anyone have an explanation of the actual operation? I suspect it has been abandoned from original function for some years, if it is a Hoffman Receiver Vent.

The returns are at most one-inch from each end of this end of row house. Seems that a Gorton #2 if not a #1 would be plenty but I have to make sure that the device is nothing more than a vent.

A device that ornate for such a mundane purpose has me wondering. The top has what seems like the body of an egg petcock without the lever. The top seems to have a ball bearing which can be depressed with my finger (or else my fingertip gave so easily), so I suspect it has a vacuum breaker function. Hence, my caution about wholesale replacement.

Adjacent to this is a vertical plugged pipe which connects to the riser (atop which is the vent discussed). This vertical 3/4" pipe connects with a tee just above the water line in that riser and rises to about eight inches below the elevation of the vent. There is a plug there now, so I suspect an air vent at one time. See the attached photo should it jog something.

While the system has been set to run at 0.50 cut-in and an apparent 1.5 cut-out, I am going to recommend as an alternate a Vaportstat and really fine gauge to supplement the code-gauge.

Insulation of all piping to be sure, replace trap guts and adding a trap on the one radiator without one... pretty straight-forward stuff.

Thanks for any insights!

Brad White_9 · May 2007

A question for the steam pros

Hey guys-

Last night I went to assess a 2-pipe steam system in an 1873 Cambridge row house. The steam system was apparently installed later, perhaps the 1910's or 20's, with the boiler (W-M EG-45) installed about 6 years ago.

Near-boiler piping looks decent but not yet compared to W-M literature. 3" riser, 2" equalizer serving a 2" main feed connecting to original 3" mains.

Just getting into this, the only issues being banging on start-up and one radiator with a spitting vent (and steam trap) and one radiator with no trap at all. Those are for another post.

My principal question is in the posted photos. There are two beautiful low radiators (American Radiator Co.) with what seems to be "Peerless" cast into the lower boss. These measure 20" high, 12.5" wide, with 6 tubes per secion with notable "fins" as the photo indicates. These are not the "tube and convector type", not that kind of fin density. Sections are 3 inches center to center. Any idea of output and history?

The other is the main vent. I could not read the casting but it has a unique shape and seems more complicated than a vent itself needs to be. (My LAOSH copy is at home right now

). I thought that this might be a vacuum device or have another function in addition to venting.

The Owners LOVE their system and want to preserve and restore it. So gratifying.

Any ideas and thoughts?

Thanks in advance.

Brad

Daniel_3 · May 2007

Hi Brad,

That would be a 20" high 11 section Peerless WINDOW radiator that can also be used for hotwater. The rating for that particular rad is 55 heating sqft steam with 5 heating sqft per section. It should measure 33 inches long. It also only came in a 6 column that could have been ordered curved or corner with the proper template given to the factory.

Brad White_171 · May 2007

Thanks, Daniel

I would have ballparked about 5 EDR per section. They are rather elegant! What is the relationship between American Radiator Company (which was cast on the top of the end section) and Peerless (cast on the lower bosses) if you know? Just curious. I would imagine Peerless either did the casting for them or were distributing them.

Thanks again!

Brad

p.s. small world in that the Owner has a harvard.edu address also.

Christian Egli_2 · May 2007

Just to ramble on - because you asked

The cast iron device looks exactly like an air eliminator - an articulated float that lifts a pin to shut a breather hole - the same devices that let air out of a hot water system, but not the water. The air eliminator does nothing except confuse everyone. It's only a safety device that prevents a flood if boiler pressure goes wild. With modern vaporstats, they aren't even necessary.

By wild I mean 1 - 2 PSI tops, or whatever is your B dimension. This is a vapor system and it will be greatly (I really mean greatly) improved by keeping the breather hole on top of the air eliminator completely wide open. Often, the old coal set up are fitted with a vacuum check; this extra constriction in not wanted in quick gas fire today.

Steam is never supposed to get this far into the returns, if it does, there are radiator traps to be fixed imperatively. Pressurizing the returns with steam gets everything to slow down. At worse you get hammer and spitting.

On the trapless radiators, it is possible the return line dips into a plain water seal. This, along with a one pipe air vent on that radiator makes it work just fine, but without the super radiator venting that comes in two pipe systems.

Bore out the nostrils on the air eliminator, but not with the fingers. There, my two bit advice.

Best regards

Daniel_3 · May 2007

That is a good question Brad. Around the very early 20's the "Peerless" rad was named "Rococo" and this simply is the design name. A&R had "Detroit" radiators as well as a few others, the "Detroit" being manufactured at their Detroit facility. The castings were manufactured at the A&R co. factories which were quite large and look to be able to handle all the castings themselves as well as every other aspect of production, no out-sourcing there

. Someone else here defintely knows the rest of that question.

Christian Egli_2 · May 2007

To drop cigar ashes all over the carpet, like Columbo would

56 inch is luxurious, anything that measures up to that is impressive to my eyes. Mainly, it makes me think that there never was a need for any alternating return receivers or either the Hoffman differential loop. This leaves us with the air eliminator as the most probable suspect.

I can't tell the brand, the logo looks like Armstrong, the bolting looks like it could be Illinois and I have a vague inkling that it may be Barnes and Jones. Your radiator trap also looks like it could be B&J. Around my parts, we have lots of systems that do have the Rococo (name, not style) Radiator of p 57 in EDR like Daniel said, and mostly these are connected with Dunham traps and air eliminator. (In my Midwest I see way more two pipes than the one pipe systems that I think you see so much on the East Coast) So, it also could be Dunham. The only one it doesn't look like is Webster (we have loads of those around here in commercial dos).

The round opening on the Webster air eliminator is placed in a vertical plane - yours is horizontal. That's a big difference. Nonetheless, the fancy hole is just big enough to fit the float. All the hinge mechanism seems attached to the inside of the lid, like it so conveniently is on Armstrong stuff.

Such air eliminators were fitted with vacuum check valves to allow subatmospheric operation of dying coal fires. A ball check. This feature is no longer compatible with rapid on off automatic fires.

As the pressure inside the boiler goes up, the returning water starts piling up the B dimension. At 56 inch, you top out at about 2.1 PSI. After that, water floods the returns and pours out the air exhaust hole. The cure: stop the pressure at 2.1 PSI.

With coal, that couldnt be done. The air eliminator went into effect and automatically closed the normally wide open air hole. With no connection to the atmosphere, there is no B dimension to measure anymore, your 56 inch becomes the familiar A dimension where only a few inches are necessary for stacking condensate back into the boiler. A dimensions are only related to pipe friction losses. B dimensions are related to PSI gauge measurements against the open atmospheric pressure.

At this point you also had to assume the air venting phase was over. It would be with a slow to start coal fire. Today, this is no longer true of automatic fires.

Phantom ends

The 3/4 appendix riser that connects to the bottom of the return into the boiler must have been a previous water feed. This was a common way to pipe it: far away from the boiler to stop a bit of cold shock; notice how it connects below the water line, a bit lower but just the way Hartford connections are made. There is no duplex of check valves with midway pumping tee connection to show this ever was part of an alternating receiver contraption.

A further clue is the newly replaced copper feed line that is in such close vicinity. Also, putting a vent hole atop the appendix riser would serve no purpose for passing gas, the below the water line connection makes this impossible. You'd only get burps and leaks.

Dangerous encounters

You mention Gortons, but on a two pipe system, there is no place for one pipe air vents. You have the radiator traps to stop the steam. Putting a steam stopping air vent at the location where air is eliminated from the system will be cause for major failure whenever a radiator trap will go bad: you'll be packing live steam into the returns - against its will - and you'll have a big fight on your hands. No healthy trap will survive, and worse, packing heat in the returns keeps the radiators cold.

Think of this system exactly the way an industrial two pipe system would look like. Steam leaves the boiler with air traveling ahead of it. All this goes down the mains and into radiators that are wide open at the trap. Two pipe steam mains are massively vented plainly through each and every radiators (One pipe air vents do nothing compared to a trap, thus the need for alternate and massive main venting on one pipe system. However, adding steam main vents such as Gortons in place of crossover venting traps to the two pipe steam main is sometimes useful, but this is not the same as adding steam stopping air vents to the breather hole of atmospheric or subatmospheric return lines.)

Back to the industrial two pipe. After the radiator and the radiator trap, everything not steam is poured down the return line that functions just like a sewer drain. It has to be vented just like a stack, slugs and double traps need to be avoided at all cost.

Then, this drain just dumps itself into the condensate return tank for further pumping of the water. Air at the condensate tank plainly comes out the top vent which is nothing more plain than a gaping open pipe of the same size as the return line. If ever anyone spots an air vent - Hoffman, Gorton - screwed on top of the condensate tank, well then, you've found the culprit. It's always the one you least suspect...

Of course, the condensate tank comes with a pump. In a home setting without the pressure needs and with a boiler room carefully placed in the basement, there is absolutely no need for pumping. Gravity takes care of everything. No pump, no need for delaying the water in an accumulation pool. Where you'd have a condensate tank, in a residential two pipe system you now have a passing pipe and where the condensate tank opens with a big hole -- you need the exact same big hole off a tee. This is where the air eliminator sits.

Air eliminators only had a purpose in raging coal fires and galloping pressures. Today, there is no need for them.

**

I find them best substituted for the same kind of piping we add to the breather hole of the condensate tanks i.e. a riser that goes up to the ceiling (or B dimension) of the basement and then back down to an open drain on the floor. Piped the same size as the returns. And importantly, its ending must be unthreaded to make it obvious it is no place for a plug. (You laugh, but Ive got plenty pictures of plugged nostrils. We cant breathe that way)

**

Breathing should occur without congestion. Two pipe returns must never ever build any kind of pressure. Anything that puffs back at you after you blow into where a trap drains is bad and calls for improved venting to the atmosphere.

**

In case of an autofill malfunction, the overflow will simply pour out within the safe confines of the boiler room where no one has thought of laying the most precious and beautiful of area rugs.

**

In case a trap malfunctions, the excess steam will spill out the same breathing hole thus clueing the owner for an important and easy fix. Wait any longer and the fix becomes expensive.

**

Catastrophes are easy to prevent.

Once you have fully atmospheric venting within the return lines, you'll be amazed at how totally silent steam is. Absolutely totally silent and quick. Only the boilerman downstairs will be humming and proudly grinning from ear to ear.

I made this sound like a lecture and of course I am preaching to the choir, so, I mean no condescension - just lots and lots of condensation.

For the obvious, trap repair / replacement is a perfect start.

Best of luck Brad, what a beautiful job to go after.

Daniel_3 · May 2007

Christian, you should have someone proofread that post and send it off to the press for printing and then wait a year or two before you consider the second and third editions

Wow! What a storehouse!

Brad White_171 · May 2007

Jaw Dropping (Cigar Ashes on my Chin)

Christian- what can I say?

Thank you for the (as usual) thorough, erudite and Eglidite treatise!

What I love about this place is that, while I was well steeped in steam early-on, the residential applications still hold enough mystery to keep it all interesting. Ever learning every day. With your post above, might I take the weekend off?

I had a feeling that the mystery vent had a vacuum function in a prior life while now standing as a relic in obsolescence.

Still, a vent is needed and while this may serve the function, what vent brand or model might you recommend in the spirit of renewing critical components?

Ever Grateful for your Brain,

Brad

Christian Egli_2 · May 2007

I recommend nothing...

The current air eliminator is not an air vent in the way one pipe air vents are. The air eliminator never stops steam, it only closes if boiler pressure goes beyond B dimensions.

Neither is there ever steam in the condensate return lines. The air venting, meaning the steam / air separation occurs at the radiator outlet, that's at the radiator trap, and no where else. Return lines are always filled with a combination of near atmospheric (sometimes vacuumized) air and water, it cannot be any different.

The same lines are drawn for one pipe connection radiators: steam / air separation is done at the radiator air vent. There is the thermostatic bellows and then, beyond the exit hole, it's wide open atmosphere... What if we'd connect a pipe to the top side of a rocket shaped air vent, and then lead this downstairs? What would we want to put, or what would we need to put on the outlet end of this hose?

The answer:

Nothing at all. Keep the open pipe as unobstructed as possible. It needs to breathe in and out.

If we do install a secondary steam stopping air vent downstairs on that hose that is already connected to a steam stopping air vent, we get the -oh-so-playful- double trap situation where the quarantined section of the return becomes bloated and stops functioning. Heat starts appearing in mysterious patterns and with lazy delays. This bloating happens on cold startup already, air is a gas just like steam and it only gets worse from there.

It is the very exact same baffling problem that constipates sewer lines that are double trapped (sometimes by puddles) and improperly vented. Nothing flows while the pipes appear very normally unobstructed.

Now put away the rubber hose theory on the old one pipe rad and we find:

Two pipe steam radiators are vented at the radiator, but the vented exhaust is not let loose into the room it is piped to the basement *** where it still needs to be released just as loosely as if we'd let it all out in the room ***. Incidentally, condensate travels along in these air venting pipes and this only adds to the jeopardy of the double trap idea.

The air eliminator sits on the hole in the basement where air returns are vented to the atmosphere. In modern gas fire operation, the B dimension will never be exceeded, thus, the air eliminator never actually shuts. By design.

It is a very fancy name for a very fancy open hole.

The air eliminator can be replaced if necessary. In modern operation, a plain sawed off nipple is the best air release hole you can imagine for the business end of the air returns.

Or better yet, pipe this sawed off nipple towards an open floor drain for when the water feed goes bad - this will avoid flooding the entire system, and pressurizing it to near street water pressure, and leaking all over the carpets upstairs, and yes, the overflow will come out the air release hole and pour into the floor drain. No big deal. I can cite cases where this scheme has saved the day. Note also, that both the air eliminator and the float operated Hoffman, Gorton, air vent would have transplanted the water overflow from the basement floor drain to any of the possibly many valve stems upstairs... your pick. This option is not available on one pipe system, but it is on two pipe - I take advantage of it.

Now for reading books

I am fully aware of the many official schematics (by the manufacturers of condensate tanks no less) that plug those air release holes with steam stopping thermostatic air vents... usually they say for stopping the remote steam that would escape from a faulty radiator trap... aieeee... that's akin to grafting a master trap in the return line to the boiler (and I am fully aware that that too is done all the time)

What do we do when we have a faulty trap that is leaking precious steam? Do I hear: Can - We - Fix - It? Yes - We - Can! Come on, sing along with the Bob the Builder jingle.

It's that easy. Trying to stop steam twice does not ever work and I read so many more stories about these caveat that I am perfectly happy to x-out official contemporary schematics of strangled return lines. I note also that the positively modern heating handbooks of Webster and Dunham never ever proposed a game of double trap double jeopardy.

Enough book wielding for now

The practical options are to 1) make sure the current air eliminator remains wide open at all times, with the back pressure of the now unnecessary check valve removed or 2) replace the gadget for a sawed off nipple arrangement from which air can breathe and overflow water can accidentally pour out, just like we do for condensate tanks. Alternately, for historic conservation purposes, leave the eliminator in place but build an additional bypass sawed off line right next to it. Leave no tempting thread on the breather hole for things to get screwed.

I hope this was more help than lecture. It applies to most all two pipe people.

For fun, I include two photographs of things that should not ever be done - the second from a boiler deep in a pit where plain open nipples worked wonders until someone could do better with four caps - the first, if you look at the far right corner of the tank, you can see the struggle some enterprising hack went through to stop steam; yet there were only 4 f&t traps to maintain on this branch... plugs stop steam too, then of course, since old boilers can't build proper pressure a new machine was installed and cranked up to the ceiling. This sort of stuff is mighty embarrassing.

Thanks to Daniel and Brad for your encouragement and for making me type.

Steamhead (in transit) · May 2007

That vent trap

looks like was made by the V.D. Anderson Co., which was located somewhere in Ohio. I don't think this was the same Anderson company that made Vent-Rite radiator vents for many years. Have you found any other hardware with names on it?

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Brad White_172 · May 2007

Hardware

Steamhead- thanks for checking in- There is a distinct casting but hard to read. I may do a rubbing of it or if ambitious, a dab of 5F5 paint remover.

Do you agree re: the function as set forth by Mr. Egli?

The one part of the system that is definitely not right is that one radiator has no trap at all. One can see what happens there.

The other anomaly is a radiator with a vent and a trap on the third (top) floor. That one spits. The system has been running at the lowest practical pressure the instrumentation can deliver (0.5-1.5).

Aside from the ARCo/Peerless radiators, no other identifiable hardware of note.

Steamhead (in transit) · May 2007

It will work

but I prefer to have something at the vent location that can stop steam from escaping if a trap fails. Escaping steam + LWCO malfunction = cracked boiler.

My guess is that the third floor rad was heating slowly and some knucklehead thought a vent would help.... trouble is, that vent has air coming at it from both the steam and return lines. Unless the return has water trapped in it or something.

What about the rad valves and traps? Any names on those?

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gerry gill · May 2007

Brad,

if you can get me any engraved/enbossed info off the objects, i can try to dig up any patent papers on it.

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Brad White_9 · May 2007

Great of you to offer, Gerry!

I will see what I can do. Love this stuff.

Brad

Assessing a Two-Pipe Steam System

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