Elimination of Boiler Return Trap

RLS

The original boiler is to be replaced. The original system dates from 1935 and is a two pipe vapor steam system.The new boiler is shorter in height and presents the opportunity to eliminate the boiler return trap. If the new boiler is to be run at 1psi is the trap necessary ? Is there anything else needed to allow the boiler to run correctly?

JUGHNE

Picture of the boiler return trap, include near boiler piping please.

Jamie Hall

To what, exactly, are you referring as a "boiler return trap"? It may be an integral part of the original system... in which case removing it will open a rather spectacular can of worms.

Second point: if this really is a vapour steam system, it was meant to operate at no more than 12 ounces per square inch, and more like 6 to 8. That's ounces. 1 psi will be too much pressure.

Third point: "The new boiler is shorter in height" -- so the water line is closer to the base of the boiler. The installed water line much match, within an inch or two, the original. Resist the temptation to lower the water line. You must raise the boiler on a pedestal to match the water lines, or install a false water line system. The former is much more satisfactory. It is very likely that when you go out in the system you will find that there are drips from the dry returns and from the steam mains which go into wet returns. Those wet returns must remain wet, or you will be dismayed to find that steam whizzes around from the mains into the returns and the system will work poorly, if it works at all.

Find out all you can about the specific vapour steam system which you are playing with before you start turning wrenches. It will pay in the end.

Danny Scully

If it’s a vapor system, I’m think 1psi is too high of a pressure to be running. Pictures always help.

DanHolohan

A return trap also has a main vent connected to it somewhere. Be sure you can get the air out of the system if you remove it.

Dave in QCA

I'm going to pose a question. How often has anyone who participates on this forum ever walked into a boiler room that still had all of its original accessory apparatus in tact, such as a return trap, air eliminator, etc. etc., and said, "Gee, if only they had stripped out all of the original components, it would be great."?

Instead, we are left trying to imagine what was there and how it was designed to operate.

Jamie Hall

Dave in QCA said:

I'm going to pose a question. How often has anyone who participates on this forum ever walked into a boiler room that still had all of its original accessory apparatus in tact, such as a return trap, air eliminator, etc. etc., and said, "Gee, if only they had stripped out all of the original components, it would be great."?

Instead, we are left trying to imagine what was there and how it was designed to operate.

Too right. And then we are left trying to figure out how to make it operate at least sort of vaguely right without the original equipment which made it operate so well... and which is completely unavailable.

the_donut

I walked into one that had a bulletin board of the previous 3 boiler installs. Couple generations of dead men I those photos.

Mike_Sheppard

@Jamie Hall question for you. If the returns were dry returns, like that Dunham system I was working with a while back, wouldn’t it be ok to lower the water line? I’m asking just out of curiousity. And if so, if there were then enough “A” dimension after the lower water line, couldn’t the return trap be eliminated? This probably isn’t the original poster’s scenario I’m just wondering for myself.

RLS

Thanks for the replies. Some additional information: The 1935 two pipe gravity return steam system has a Marsh return trap with a sight glass and a Marsh #11 air eliminator. I contacted Marsh and learned these parts are no longer available. And of course these parts are not working either. What is to be done next?

jumper

DanHolohan said:

A return trap also has a main vent connected to it somewhere. Be sure you can get the air out of the system if you remove it.

Yes you have be able to get air out of system somewhere and condensate back into boiler. An adequate B dimension should suffice to do the latter. At least I hope so.

Mike_Sheppard

@RLS look up “Condensators” from Barnes and Jones. Steamhead told me about these. I don’t know if they’re available any more or not.

Jamie Hall

Mike_Sheppard said:

@Jamie Hall question for you. If the returns were dry returns, like that Dunham system I was working with a while back, wouldn’t it be ok to lower the water line? I’m asking just out of curiousity. And if so, if there were then enough “A” dimension after the lower water line, couldn’t the return trap be eliminated? This probably isn’t the original poster’s scenario I’m just wondering for myself.

You can, @Mike_Sheppard . Provided -- and this is the biggy -- you make one hundred percent sure that any wet returns stay wet. It was very common for there to be drips from the far distant ends of steam mains and from their related dry returns, far out with the spiders and the snakes at the end of the coal cellar. Or some similar place. And those wet returns were often pitched back to the boiler.

But... so long as the lowered water line is still high enough to keep them wet, you should be fine.

On @RLS 's problem. No surprise there. There are a few companies which still make their old stuff -- Hoffmann is one -- but most don't. The best thing to do now is to take a deep breath and sit back and figure out the best way to make it work as it was meant to, but using modern parts. The general principles are, after all, much the same: you have steam mains which go out to the radiators and, almost always, to crossover traps which go to related dry returns. The dry returns may or may not come together in one place (I think in the Marsh they did) at or near the boiler, where they drop to the boiler. That is the location to put really healthy main venting. There were almost always also wet returns which picked up drips from the steam mains and the dry returns. Those -- as I said above -- must be kept wet. No options there!

The crossover traps are critical -- they just aren't optional. They're also usually easily repairable, if they fail.

The gadgetry -- like the boiler return trap -- was usually there to protect the system from excessive pressure. These things were meant to run on only a few ounces of pressure, and so long as you keep them there you don't really need them. To which end one must use a vapourstat, properly calibrated (you need a low pressure gauge) and it's not a bad idea to use two, if the gadgets are gone. Plus a backup pressurestat (and I prefer a manual reset on that). The air eliminator is basically a big main vent. I would suggest an appropriate number of Gorton #2s where the dry returns join, or on them separately if they don't join. Why Gorton rather than Big Mouth? So that if the pressure gets to high you don't get a shower. But that's my preference.

Jamie Hall

Oh and one more thing. Size the boiler right and insulate all the mains. Do not oversize the boiler. Size it by the EDR. If you have a choice of one slightly too large and one slightly too small, go with the one slightly too small -- and insulate the mains. Put a good header on it; you can't skimp there.

Dave in QCA

If you proceed with your plans to remove the return trap and the air eliminator and it sounds like your mind was already made up, at least put them for sale on Ebay or something like that. Don't scrap them. I've been looking for similar components for a Dunham system and only after 10 years did a friend come across a air eliminator for me.

Back on the subject of removing these devises, you say that they are not working and that parts are not available. Granted, parts certainly are not available, but are you sure they are not working? The return trap, if not working, will have 2 possible symptoms. One, is the steam valve inside does not close properly. This will result in steam leaving the vent pipe to the air eliminator and then escaping that device through the air vent port. The second symptom would occur when pressure in the boiler is high enough to cause condensate to back up into the returns to the point that the reservoir chamber in the return trap is full. If the trap fails to cycle at that point, that indicates a problem. When boiler pressures are low enough that condensate returns by gravity, the return trap does nothing but set there and cause confusion to people who think its not working.

As for the air eliminator, it is a simple float device. If condensate backs up into the float chamber, it causes the air port to close so that condensate does not come out of the air vent port. At all times when there is no condensate present, it just sits there and does nothing.

I agree with most advice that has been given. But to simplify things, if you have standard pressure limiting devices that are set at the conventional residential limit of 2 psi (give or take), you need a B dimension of about 6-7 feet to assure gravity return. Note; B dimension is the difference between the normal boiler water line and the lowest point of the horizontal dry return piping before it drops to the boiler return connection. if you have a B dimension that is less, you must have an alternate means to return the condensate to the boiler when pressure is high. Such means could consist of a return trap, a condensate pump, or a boiler feed pump. The other option is to precisely control the steam pressure at a lower level with the use of a Vaporstat.

Jamie Hall

Well said, @Dave in QCA

jumper

Jamie Hall said:

Well said, @Dave in QCA

Agreed except that there can be exceptions to "to simplify things". One is that in a vapor system with no traps at all the B dimension only has to overcome pressure loss through the heating system. So maybe if OP is heavily into trap elimination.....