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Boiler replaced - Boiler trap removed

TDubbTDubb Member Posts: 5
I'm hoping someone here can lend a little advice on a problem project I have been drawn in to. I have done a fair amount of work on residential steam heating systems and boiler replacements in the past but I do not consider myself a steam expert by any means. I have a basic understanding of the operation of the system I am now trying to repair but I don't have enough knowledge to feel confident in a repair.

My customer had their old oil fired steam boiler replaced with a new gas fired steam boiler by another contractor several months ago and claims it has not worked since the day it was put in. The other contractor has been making attempts at finding a fix but with no luck. From the descriptions of the old system that the customer has been giving me, it appears that there was originally a boiler return trap in the system. The installing contractor removed it during the course of the installation and replaced it with a new F&T trap. A dry return pipe, which is the return from all of the radiators, enters this trap then exits and is piped straight into a return tapping of the boiler. Another return pipe, which originates from the end of the supply main, comes in low and is piped into a Hartford loop and into a return tapping on the other side of the boiler. All of the piping near the boiler, both supply and return, has been replaced with copper and there are no check valves left in the system.

My suppliers have told me there is no possibility of getting my hands on a new boiler return trap. From researching as much documentation as I've been able to get my hands on, it appears the system will never operate properly without it. My thought process has been that I could probably reengineer this system with a receiver and condensate return pump but I don't want to make this expensive leap without some input from those with more knowledge of this design then I have. Does anyone have any experience with boiler return traps and what to do with the systems if they are removed?


  • Jamie HallJamie Hall Member Posts: 6,706
    From the sound of it...

    this is at least a two phase, if not more, knucklehead job.  Which mean that getting back to where it should be may take some real detective work.

    But fear not, it can be done.

    First things first -- all that copper for the new near boiler piping is just plain wrong.  Whether the routing of the pipes is right or not is moot.  The material is wrong, and has to be replaced in threaded black iron.

    Further, it has to be replaced in accordance with the diagrams and specifications from the manufacturer -- or better.  No compromises or skimping on sizes or dimensions.

    Now.  That will give you a boiler, delivering steam through a riser or risers, to a header.  From that header one or more steam mains will depart, as well as an equalizer at the far end, which will go back to the Hartford Loop connection and from that down to the boiler return.  The steam main or mains will go out to the system, and a return or returns will come back and tie together before the Hartford Loop, come up to the Hartford Loop, and thence back to the boiler.

    So far so good.  First question: is this one pipe or two pipe steam?  It makes a difference.  In either one pipe or most two pipe systems, there needs to be main venting at the ends of the steam mains.  In one pipe steam, there are also vents on the radiators; in two pipe there are not, but there are vents on the dry return(s).

    In one pipe steam, condensate returns from the radiators to the same mains the steam came from.  In counterflow systems, all the mains slope down towards the boiler, but before they get to the boiler there has to be a drip connection from the main or mains down to a wet return.  In parallel flow systems, all the mains slope away from the boiler, and there is a drip connection down to a wet return at the far ends of the mains.  In these systems, no trap is needed anywhere on the system.

    In two pipe systems, air and condensate comes out of the radiators via the return connections.  In most systems, there are traps on the radiator outlets to keep steam from getting out; in some vapour systems, there are no traps -- nor are they needed, as the pressure and sizings and fittings also keep steam from getting into the returns (provided the steam pressure is correct).  There is no steam in the dry returns, and hence there is no need for a trap on the dry returns.  Nor is there a need for a trap or check valve on the wet return.


    Where are we?

    I would be helpful to have some pictures of the near boiler piping -- even if it all has to go -- and a diagram of the rest of the system.  Also, of course, whether it's one pipe or two...

    We look forward to that -- then we can probably help a lot more.

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-McClain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • TDubbTDubb Member Posts: 5
    A little more info

    Thanks for responding Jamie. This is a two pipe steam system. The radiators are all equipped with steam traps and none have air vents. There are two steam supplies leaving the boiler. They both start at their high point above the boiler and pitch away, down to the end of the main. At the end of the main the pipe reduces in size and drops vertically down the wall then pitches back to the boiler where it enters the right side of the boiler with a Hartford loop. The dry returns start high at their far end and pitch back to the boiler where they join before entering the new F&T trap that was installed. From the trap the return drops down and enters the left side of the boiler. There is one air vent installed in the return just before the trap. This was installed by the contractor who did the boiler replacement as one of his attempts to fix the system. The customer does not believe there was a vent there originally. Other than that I have seen no other air vents in the system.

    From the description the customer has given me I believe there was a mechanical return trap originally installed in the location where the new F&T trap is now. He describes it as a large, sort of square device that had a support pipe that dropped to the floor to hold it up. He also believes there was a small steam line feeding from the main into the top of this device.

    I am attaching some pictures I took of the near boiler piping. As you will see I am going to need to do quite a bit of repiping to get rid of all that copper.
  • ChrisJChrisJ Member Posts: 8,630

    It looks like they did get the pressure relief valve piped right at least.  Everything else on the other hand...

    I see the water heater doesn't have a drip leg on the gas piping, can't see if the boiler does or not.  Is it acceptable to reduce the flue pipe like that at the wall?
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment

    Steam system pictures
    Central air project pictures
  • TDubbTDubb Member Posts: 5

    You're picking up on a lot of things I saw myself. I didn't bother mentioning any of them because I understand those fixes. I'm not touching anything on this system though until I get this steam issue worked out. Relatively speaking, the rest is a piece of cake.
  • ChrisJChrisJ Member Posts: 8,630

    Sorry bout that. :)

    Though I am curious about the flue, is that acceptable or not?  I'm asking because I'm not a pro and am curious.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment

    Steam system pictures
    Central air project pictures
  • JStarJStar Member Posts: 2,668

    A Boiler Return Trap and a F&T Trap are not the same thing! Right now, there is no way for air to leave the system/radiators. Get rid of that F&T trap, and install a heav dose of main vents. Then fix that horrible mess of piping, getting rid of the copper at the same time.
    - Joe Starosielec
    [email protected]
  • RobGRobG Member Posts: 1,850
    edited June 2014
    Am I Nuts?

    It seems that in one picture the main is going into the chimney. Then in another picture it's not. Needless to say, it is some F......ed up piping. I just seem to lose myself going from one picture to the next. there is an f/t trap in one picture and not the other?

    And no, that venting is not correct. The water heater is also tying into the reduced vent.

    I am still wondering about the main / header?  running through the chimney
  • RobGRobG Member Posts: 1,850
    Gas Cock

    And while you're re-piping, put a gas cock on the water heater.
  • TDubbTDubb Member Posts: 5
    edited June 2014

    I have lots of things to do to make this one right. The problem is that until I figure out what to do about the missing boiler return trap the rest means nothing. At this point the boiler only runs a few minutes before it runs out of water. The pictures aren't the best but the F&T trap is there and it's definitely not the right trap for this application. The piping job is almost as bad as it looks but it doesn't run through the flue.
  • Jamie HallJamie Hall Member Posts: 6,706
    edited June 2014
    I, at least,

    don't think you need a boiler return trap.  If a two pipe system is properly piped in residential sizes, the only traps needed are on the radiators.  I think you really need to think through the piping beyond the boiler -- as well as the boiler -- and see if you can figure out how it might have been piped originally.

    There are several possible causes for the boiler running out of water after just a few minutes, but there are only two classes of them.  Either the pressure is much too high, and the water is backing out of the boiler and hiding in the returns, or the piping is seriously wrong with the same result or with the water being carried out into the mains.  Or some combination.  Check the pressure -- anything over two pounds is too much; quite possibly way too much.

    I might add the contraption which was removed may not have been a trap of any kind.  If this was originally a vapour system -- which is quite possible -- there are any number of contraptions which fit your client's description which were not traps, but which served to make sure that condensate returned properly to the boiler.

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-McClain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • BobCBobC Member Posts: 4,453
    Bad near boiler piping

    It's no wonder all the water is leaving the boiler the way it is piped. The header configuration is wrong, the equalizer is badly done. I suspect the water line is bouncing around and the boiler water may be filthy.

    No mater what else happens the near boiler piping has to be completely redone in threaded steel if you ever hope to have a stable waterline, then add Gorton #2 main vents for each main - each main should be fed from the boiler header separately. The boiler then has to be skimmed to get rid of all the oils that will be introduced to the system. Also the pressure should be kept very low (ounces) and that means throwing out the pressuretrol and installing a 16 oz vaporstat.

    You also will need venting on each main or it's return, the pipe diameter and length will tell you haw many. You may or may not need a master steam trap but as long as all the radiator traps are working you might get by without them. Some of the pro's on this board will be able to tell you what the best course of action to take.

    good luck,

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • ChrisJChrisJ Member Posts: 8,630
    edited June 2014

    I suspect it may be easiest if you pipe that boiler similar to how I piped mine as it looks like the mains line up in the same fasion.  Have a look at the pictures found in the link of my signature.

    I used two 2" risers out of the boiler into a 3" drop header, though if I could redo it I'd probably run 3" out of the boiler part way into reducers as it may produce drier steam and wouldn't cost much more.  Not sure what size tappings the boiler you're working with has, many only have 2".
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment

    Steam system pictures
    Central air project pictures
  • TDubbTDubb Member Posts: 5
    If I understand correctly,

    the thought is that I don't really need a boiler return trap on this system? My understanding was that the return trap was needed to overcome pressure in the returns to force the condensate back into the boiler. The diagrams I have seen of these things show a steam supply line entering the top of the trap and a check valve on either side of the tapping where the trap is piped into the return.

    Is the idea that if the system pressure is maintained low enough with a vaporstat and the returns are vented at the point where they drop down to the boiler, that gravity will do the rest? There were no air vents installed in this system originally. Are the check valves no longer required if the piping configuration is changed to this setup? Do the two dry returns get piped down into the wet return before the Harford loop?

    Sorry for all the questions but I don't want to be experimenting with this. I would like to know I'm taking the correct steps to repair this mess before I get started.
  • Jamie HallJamie Hall Member Posts: 6,706
    As I noted in my first reply

    I think you are looking at a system which has had at least two stages of knuckleheads... if not more.

    First off -- air vents of some kind, somewhere, are absolutely required.  In two pipe systems which have been "modified" over time, the easiest and most reliable approach to venting is good big vents at the ends of the steam mains and another set at the ends of the dry returns, just before they head down to the boiler.  The objective of the steam main vents is to allow steam to move rapidly to the ends of the mains, thus allowing all the radiation to start heating uniformly.  The objective of the vents at the ends of the dry returns is to allow the air leaving the radiators to go somewhere, and thus allow the steam into the radiators.

    All this should happen at very low pressures -- a few ounces or so, maximum.

    On residential systems, if is almost never necessary to have any kind of fancy gadget to get the return condensate back into the boiler -- assuming just one thing: that you have adequate (read: vaporstat) control of your pressure.  Gravity is astonishingly reliable, and all you need to do is give it a chance.  So yes; the ends of the dry returns should all drop down and join whatever wet returns you have before the wet return connects to the bottom of the Hartford Loop.

    At this point it is worth wandering around in the basement and checking to see that all the wet returns are, in fact, wet -- that is, below the water level of the boiler.  Sometimes when boilers are replaced the water level is lowered, which can dry out some of the wet returns, with lamentable results.

    The comment on the fancy gadget arises because in older, coal fired systems, there often was a fancy gadget at the ends of the dry returns (or sometimes elsewhere) to ensure that if and when the pressure rose to high that the condensate could get back to the boiler while at the same time still allowing air to escape.  They were needed because it was harder to control the pressure in a coal fired boiler; they don't turn off quite as neatly as oil or gas burners do.  There is no reason to take them off, however, if they are there -- but equally no reason to put them back on if they aren't.

    Again, though, use a vapourstat for control!

    As others have noted, the near boiler piping does leave something to be desired...

    In response to direct questions: no, no check valves are needed.  Gravity will do the job.  At one time, there was some means for venting this system, which has been taken away.  The boiler return trap is not needed.  The two dry returns drop to the wet return before the Hartford Loop.

    And, if you haven't already bought it, I highly recommend buying at least "The Lost Art of Steam Heating" available on this site.

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-McClain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
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