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Bioler Return Trap & Alternating Receiver

I would say yes re-pipe them. If you don`t and your new boiler WL is below this tee, the condensate in the return main will flood the new boiler to this height.<BR>Remember, the B dimension is taken from the boilers waterline, if you change-it the BRT tie-in point will have to follow suit.<BR><BR>Dave


  • Tom Minz
    Tom Minz Member Posts: 18
    I'm confused!

    I've attatched a picture and a paragraph taken directly out of chapter 15 of Dan Holohan's "Lost Art..."
    I'm replacing an old boiler with this exact setup.The new water line is a good 2 ft. lower than the old water line. the end of the main loop seals are still well below the new water line....but....
    Question: Do I need to re pipe the inboard and out board swing checks at and 12" below the "new" water line in order for this system to work?!Thanks for any help.

    Tom Minz
  • Tom Minz
    Tom Minz Member Posts: 18

    here is a smaller file so it doesn't take so long to download. Please does anyone know if these check valves NEED to be at and below the water line. I'm thinking they only come into play when the pressure exeeds 12 oz. With a a Vapor Stat set @ 8oz, they should sit there quietly until they are needed, which if all controls are functioning well, that should be never. Am I way off base here, or will leaving them in the existing location not cause a problem....Please help.

    Tom Minz
  • Tom Minz
    Tom Minz Member Posts: 18

    Here is a smaller file so as not to take too long to download. Please, do these check valves need to be repiped at and 12" beloww the "new" water line. I'm thinking the y don't come into play unless the presure gets too high. with a vapor stat set at 8 oz. i'm thinking they should just sit there quietly until they are needed. If all controls are functioning properly, that should be never. Am I way off base here, or will leaving them in their existing location cause no problem....Please Help

    Tom Minz
  • Christian Egli_2
    Christian Egli_2 Member Posts: 812
    Elective cardiac surgery for the alternating receiver trap

    No faulty logic to give queasy feelings to anyone. Pumpless condensate pumps work like magic - when they're needed. And they are needed only when the boiler pressure is speeding over the B dimension. Today simple math determines what is a safe number. That wasn't so easy to respect in the olden days of live fires. Coal was the real thing.

    Tom, you clearly seem to have a good handle on what your B dimension is and how not to ever exceed it. The big detail that mustn't be missed is from where we measure the B dimension.

    Top side - easy: the bottom of the lowest dry return.

    Bottom side - careful: it could be the boiler water line... it could be something else... you know... it depends...

    Many alternating return traps have both their heart valves piped anywhere below the water line, usually near the floor, well bellow the Hartford connection. Needless to say, the heart shaped cast iron organ is useless without functioning valves, I think keeping them well below the fluid level is better at preventing flutter. At any rate, the diagram you produced shows an arrangement were the exit valve sits at old high boiler water level. Let's not care about the low set inlet valve for now.

    Let's suppose you keep this original setup, with the exit valve sitting up high and you drain the outlet piping down to your new low level, if you imagine the stream of water pouring down the return you'll obviously see how that high set valve has in effect become a new false water line. Ah ha.

    Your new B dimension would still be exactly the same as the old one (24?) inches or whatever else it may be. This would negate the benefit of going lower with the new boiler water line because it wastes at least half of the now available B height. Too much pressure, we'd just count on the alternating trap to do its job... no problem, but why? Stacking B heights are always a shame to waste.

    (Technically, depending on how your equalizer connects to all this, your newly exposed false water line could be either of the outlet valve level or the old level Hartford connection - they vary by just 1-2 inch, I'm skipping over that detail)

    Moving the valves, what Dave meant, is the way to increase your full B dimension potential and maintain the safety operation of the alternating receiver on wild pressure, and also remove potential for flutter. Had the original valves been set near the floor as in so many typical installations, we wouldn't be typing this now.

    -- Transplant operation

    Fortunately, cast iron cardiac valve transplant surgery is painless. Even while maintaining all vital functions. Working around the receiver stem, abandon the exit piping up to the outlet valve. Also abandon the inlet valve. We won't need to touch the vertical stem itself. With a sharp scalpel it all comes out easily. Now we have several veins to reconnect: the return line that ends at the old dirt pocket, the new boiler Hartford connection and two holes on the alternating receiver stem. Most simply start at the old dirt pocket, pipe it near to the floor, don't forget to insert a new dirt pocket and also a port hole for dirt flushing purposes. Then go horizontally, through the new inlet valve, then horizontally to a tee, then straight through the tee a bit further to the outlet valve. Then, you're free to go back up to the Hartford nipple - insert again a dirt pocket on the up step, dirt pockets are good.

    We still have the open tee. Connect this with pipes going upwards to one of the two holes we have on the receiver stem. Plug the other old hole. There is only one pipe protruding from the bottom of the cast iron ham, it makes no difference how far we go extending this one pipe down to the new valve level. Just make sure the pipe vents upwards and that air bubbles cannot get trapped in an inverted U kink that would look like an air seal. Important. Nowhere in the new layout should you ever cause air to be trapped. This is real easy to avoid. Exit side, it vents to the equalizer, stem side it bubbles up to the receiver which is self vented, inlet drop side it vents most naturally to the air eliminator.

    Doing this most simply extends B height to maximum value and it maintains the alternate receiver operation. How can you go wrong?

    There is also another procedure: the heart bypass surgery.

    -- Bypass operation

    Do this only if you know for sure your system doesn't need to operate at any pressure higher than your available B size.

    Leave everything old in place, keep it there in case it really was vital and needs to be put back in service. Maintain the old Hartford connection which will now be pouring into a dry drop - nothing wrong with that, what you have is exactly a false water line that maintains your old B dimension exactly the way it was before you dropped the boiler. You could do nothing else and let the patient survive without the new life the new extended B dimension provides.

    To get full B use, install a bypass return from the inlet dirt pocket to your new boiler inlet. This bypasses both check valves. Pick up the connection from the old equalizer line on the way. Dirt pockets, port holes, blah blah. Add also a valve on this bypass. This new straight connection affords full use of B stacking heights without the backpressure of the two heart valves. This makes for simple system operation and if you should really really need more pressure, call for the return of the pumpless pumping action by simply closing the bypass valve.

    The drawback to this, is that you need to know your homeowners will figure out whether to keep the bypass valve open or shut, you'll always have to remind them.

    I think I would go for the valve transplant and I would try to reuse the old check valves after a good reconditioning of the internal mating surfaces. If you get new ones, make sure they open with nearly no backpressure.


    I want to go on and give more advice: make sure your patient is still breathing.

    Focus on the air eliminator, remove the vacuum check valve and replace it with a cut off nipple. This is the only nostril the entire system has for exhaling all air from all the mains and all the radiators. You need a clean nose free of any boogers. With rapid electric controlled burner operation a big open breathing hole is key.

    Steam is stopped once at the radiator thermostatic trap - you can't stop it again further down the returns without asking for trouble. Double trapped steam always goes into a destructive fury that pounces on harmless bystander traps. Letting this happen over and over is an expensive joke.

    If ever steam (not just a whiff of vapor) comes out the breathing nostril, make sure the owners know to call for quick and easy repairs on the radiator traps.

    To know if the patient is breathing enough to be alive, perform easy CPR. Blow into the system, say at the boiler relief valve and watch what comes back at you when you release your mouth. If there is a cough back, it means you can benefit greatly from poking the nostril into a larger hole (assuming also all your traps aren't busted shut). If everything you blew in comes back at you, you are having serious congestion, your vent hole is probably plugged. Fixing this is imperative. If nothing comes back and an delightful assistant perched over the air eliminator feels your blow of air, you have a very healthy system. Try blowing harder.

    It is really amazing how easily our very own human lungs can pressurize these wild steam pipes: they were built to operate on maximum 0.5 PSI head loss. We easily blow to 1.5 PSI. Enough to tear down the place.

    Now, Tom, go do the Frankenstein act, wait for a stormy night, then, from the depth of the boiler room, revive this steam system.

    I hope this helps. I attach some A.R.T. work for clarity.
  • Tom Minz
    Tom Minz Member Posts: 18


    Thank you for taking the time for giving some extremely valuable (and knowledgable)input on this old system.

    As you mentioned, my concern was with the outboard check. What is it going to do? Flutter , chatter, wake up a sleeping home owner...realizing I would be depending on the original B dimension if I leave it in it's original position.

    You are also correct when you said , with a sharp scalpel, surgery is painless. As with any surgery,no matter how sharp our scalpel is, its vital that we cut in the right place...and thanks to this site and knowledgable people like you who frequent it, I'm confident the I will perform the surgery with out a glitch and I expect a full recovery!

    Thanks Again ( until I stumble upon another old system....there is quite a few still in operation in my market) for your expert advice!


    Tom Minz

    P.S. Great Drawing!
  • Fred Harwood_2
    Fred Harwood_2 Member Posts: 195

    Tom, with a Vaporstat all but the vent can come out. Because your pressure will never stack condensate up to the drip of the main or the dry return, all that iron becomes superfluous. As for the vent, get rid of that check vent as well, and let the return breath though as big a hole as you can arrange (assume traps function).
  • Christian Egli_2
    Christian Egli_2 Member Posts: 812
    Murmurs at best

    Hoffman makes a big do about this check valve flutter (if that's an appropriate word) on their vacuum line installations. I don't think it is ever a noise issue, at worse it is an issue with getting tight seal. Documentations on vacuumizers show their kinky approach to check valve installation.

    Personally, and I don't know why really, I prefer having my check valves sitting idle in exactly the same fluid they get to see when in action. If the checked line is only for handling a gas, then I don't like drowning the check valve in a water trap (this is the Hoffman obsession in vacuum lines). If the valve is for liquid control, then it is best not to trap the gadget in an air pocket. It is a way to think I have my check valve ready and primed for the job - whenever it may come.

    Note, noisy check valve chatter on pumped lines is something else altogether -- here in this post there is no power pump, and the extra low pressure alternating receiver does not qualify as one either.

    Really the important thing in condensate and air return lines is to not have water pockets in dry lines and not have air pockets in wet lines. It is so simple and yet so hard to keep it straight.


    To add one more comment. What I playfully described as the ART bypass surgery is exactly the sort of decommissioning Fred referred to minus the cast iron removal. I don't disagree with Fred in the slightest, except for not holding on to the old stuff... it seems so hARTless... :)

    Humor aside, it is never funny to drop the cast iron ham on the foot and neither is it funny at all to discover, a bit too late, that the two pipe system imperatively has to be run on more than 1-2 PSI. This happens often enough in two pipe deals where there are condensate lifts. Lifts that are never obvious to spot either. Mostly, it is not the traditional old install that will come up with these oddities, it is the remodels where condensate returns were lifted.

    If the ham has been carved off the bones, you may be looking at a condensate tank and pump purchase... and who wants to use electricity. That's why I inserted a valve on my bypass return line.

    Thanks Tom for the kind word.
  • Tom Minz
    Tom Minz Member Posts: 18

    I agree with Fred too. With an an aditional 2 ft. of B dimension and a Vaporstat the ham really isn't needed. But( i think Dan Holohan may have said something like this), those curves, those beautiful curves! I don't think I have it in me to gut this beatiful old system.
    Another thought. If I was going to be the only service man in that boiler room ever again, then i wouldn't worry about it. However,I think it's inevitable that someone will walk up to that boiler and say ( I can here it now),
    " There's your problem. This system is not building enough pressure! I'll swap out this vaporstat and put in a pressuretrol and give it ALL the pressure it needs! It's a BIG house ya know!"
    Even tho the problem might be a bad trap in the system. or low gas pressure...or whatever!
    I think I'll leave that beatiful thing in place, just incase its ever needed.Thanks again to all!

    Tom Minz

  • I think it`s very,

    admirable of you to keep the BRT/AR on the system, they are a work of art. And Christian(Dr. Egli`s) description and attached drawing is nothing less than outstanding! Obviously you want to keep this in working-order, and the possibility of someone else coming along and "cranking-up" the pressure is a reality . However, I would be very leary of introducing return condensate(even though a trickle provided the traps are OK), above the new boilers WL, and we all know how well manually operated bypass valves work out.
    Myself, I would still move the CVs and eliminate any possibility of probs.

This discussion has been closed.