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Boiler Bypass

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FWDixon
FWDixon Member Posts: 78
I have an old Burham RS-112 boiler that was converted over to ng a decade ago supplying hot water to my 75 year old converted overhead gravtiy heating system. I've been reading everything I can get my hands on since I've been having problems getting a warm (60's) house this winter (bought the house before turkey day last fall). One thing that I've seen a few times is that these old gravity systems need to have a boiler bypass installed in the system, otherwise something not so good will be happening (in addition to heating a large volume of water).



So, I'm wondering while I save up to buy every book for sale on this site re: hydronic heating, why is the bypass important, should I have one, and what should I talk to my plumber about when contracting the work?

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  • SWEI
    SWEI Member Posts: 7,356
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    Boiler bypass

    allows some water to return on a "short circuit" allowing the boiler to heat up more quickly and reduce flue gs condensation.



    The right answer is either a thermostatic boiler protection valve (ESBE, Caleffi, LK Armatur) or a properly controlled mixing valve and additional pump.
  • SWEI
    SWEI Member Posts: 7,356
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    Converted gravity systems

    when properly fired and controlled, will beat most new systems for both efficiency and comfort.



    More details, and perhaps some photos of the boiler, the pump(s) and associated piping?
  • FWDixon
    FWDixon Member Posts: 78
    edited February 2014
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    re

    Here is a diagram of the heating system as best as I have it figured at the moment. The radiator valves are all on the rad outlets, and the living room rad only the supply end gets warm (not hot), and the office rad is always cold (haven't figured that one out yet).
  • FWDixon
    FWDixon Member Posts: 78
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    pic

    Here is a composite pic of the boiler.
  • FWDixon
    FWDixon Member Posts: 78
    edited February 2014
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  • SWEI
    SWEI Member Posts: 7,356
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    Diagram

    shows the circulator pumping into the expansion tank, which should be changed.



    Your piping diagrams lead me to suspect you may have some interesting valves on those radiators.  Can you snap a photo of a radiator inlet and one outlet?



    Boiler composite photo works except at the bottom right.  What kind of Krazy Kwilt did that?
  • FWDixon
    FWDixon Member Posts: 78
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    re

    The lower right was my attempt to include the side of the boiler showing the return inlet, circ, and burner assy. I admit it does look weird. Here's the original:



    https://lh4.googleusercontent.com/-mGvbgXPVmJU/UvZ8QSd0IgI/AAAAAAAACRY/87fh4rLFgAA/s512/IMG_20140208_134507.jpg



    There is no valve on the inlets, just a rather large dia supply pipe and elbow (I'm guessing 1" pipe as the ext looks to be about 1 1/4"). The outlet valves look like this one (snagged this from the site as I'm not at home atm)



    http://www.heatinghelp.com/images/posts/673/resize_radiator_valve.jpg
  • FWDixon
    FWDixon Member Posts: 78
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    re

    I'm thinking about moving the pump but not sure if I'm wanting to set up a primary/secondary on the system. I definitely want to re-plumb that whole area as the Domestic water (hot and cold) are approaching rat's nestish and really bother my sense of order.
  • kcopp
    kcopp Member Posts: 4,440
    edited February 2014
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    primary /secondary....

    is really the way to go. This way you provide some measure of protection to the boiler and can control the flow to the radiation. It is very important to try to mimic the gravity flow out to the system  Over pumping will result in poor heat transfer and a  less efficient system. That looks like a #30 extrol tank...generally not big enough for a gravity system...
  • FWDixon
    FWDixon Member Posts: 78
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    Tank

    It is an extrol, but some enterprising individual decided to paint the boiler, pipes, and tank and painted over all of the data plates....How can I determine the proper size tank?
  • FWDixon
    FWDixon Member Posts: 78
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    Air Sep

    Thx for the help on the extrol, may upgrade to the EX-60 this summer.



    I need to replace my air vent, I have a Taco air scoop now. Should I just replace the vent valve and nipple or would a B&G Air Separator give better performance?
  • SWEI
    SWEI Member Posts: 7,356
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    Air separator

    would best be replaced by a combination hydraulic separator / air separator / dirt separator.  If you eventually intend to install an ECM pump, I'd add magnetic to that list.



    B&G makes one with the first three (they call it a Primary Secondary Header or PSH.)  Caleffi makes all kinds, including a new one with all four (they call it a SEP4.)
  • Eastman
    Eastman Member Posts: 927
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    magnetics

    What's the connection between an ecm pump and the magnets?
  • SWEI
    SWEI Member Posts: 7,356
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    ECM pumps

    use very strong magnets in their rotors.  Ferrous tidbits have a tendency to stick to them.  Old systems are full of ferrous tidbits.
  • FWDixon
    FWDixon Member Posts: 78
    edited February 2014
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    Sep.

    I have been reading about the Sep4, but this isn't something I am able to do in the near future due to cost. But my current air vent has a fair amount of corrosion on the nipple (I think largely from the pipe being painted by a previous owner) which is why I am needing to replace it in the short term.



    Short Term goals (least cost): Replace Air Vent/Sep, Install Boiler bypass, move circulator, clean rads, clean flue.



    Long Term: Switch to primary/secondary system using the Sep4, install Indirect DHW, and replace current boiler with 2 smaller units in parallel (we only have a week or 2 of sub-freezing temps, and constantly firing a 125MBTU boiler is expensive).



    I also want to re-evaluate the diameter of the pipe connecting my boiler to the heating system. The old cast-iron pipe from the original system is 2 1/2" OD that is reduced to 1" OD (3/4" pipe I presume) pipe to connect to and from the boiler. Of course the pipes connecting to the radiators are all different depending on the size and location (on the system) of the rad, which is pretty interesting considering what went in to determining all that.
  • stufine
    stufine Member Posts: 13
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    Can he

    move the expansion tank to the return side without moving the pump?

    I'm asking for myself also, my water fill feeds into my return line and the expansion tank connects to that line 10" before it enters the 2" line
  • SWEI
    SWEI Member Posts: 7,356
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    Future plans

    should include a properly sized mod/con boiler.  By the time you factor in the associated piping, pumps, valves, and controls needed to make dual conventional boilers behave well, you'll spend less on the mod/con.  A fire-tube design can usually be direct pumped on a gravity system, removing the need for hydraulic separation.  You'll still want the magnetic air/dirt separator, but those cost a bit less.
  • FWDixon
    FWDixon Member Posts: 78
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    Mod/Con

    I have heard so many conflicting statements about using Mod/Con's on retrofitted gravity systems. I initially had in the plan to convert to one, but then was talked out of it on another industry forum, only to see them recommended often here. So at this point color me confused...



    I've done two heat load calcs on my old house, and the average is roughly 56MBTU (Manual J put me between 44MBTU and 49MBTU depending on Tightness, slant fin had me a 64MBTU). I have about 54MBTU of heating area on my existing rads, and about 4750 HDD (70 deg)(Manual J) with the coldest nighttime temp being around 13 on average.
  • SWEI
    SWEI Member Posts: 7,356
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    Conflicting statements

    We have seen plenty over the years.  Once you eliminate repetitions of "something somebody else said" it almost always boils down to improper product selection, improper installation, or improper commissioning of the boiler.  The first generation of mod/con boilers were based on high resistance water-tube HX designs that absolutely required primary/secondary piping and were introduced into a market full of wholesalers and  installers that had no experience with this type of product.  We're still dealing with those problems, and our distribution channels make it almost impossible to mandate proper training and education.



    The current generation of boilers are better built and include far better onboard controls.  The fire-tube HX design pioneered by Triangle Tube is now available in boilers from almost every major manufacturer.  This design has almost no head loss and is far more forgiving of knuckleheaded installers.  A good installer is still the most critical part of any job, but the kind of overt failures which underlie a lot of the myths about mod/cons are much less likely to happen with newer boilers.  I have several brands I am comfortable recommending and supporting on a 15-year design life.  A well-designed emitter system should last 50 years or more, but our current situation with energy price volatility and technological progress makes me advise that the heat source be re-evaluated on a shorter cycle.
  • FWDixon
    FWDixon Member Posts: 78
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    Installer

    "A good installer is still the most critical part of any job, "



    Therein lies my problem...I have had zero luck finding even a semi-competent repairman in my area (I've used the locator tool on here an other sites as well as a lot of phone calls), which is partially why I'm starting to look to do at least the more routine stuff myself. But replacing a boiler is so far more than I'd even consider.



    Anyhoo, I've kind of veered off track, but what should I consider when installing the bypass on my current boiler, is the 3/4" pipe connecting the supply and return plumbing on the original system adequate, and should I replace the air vent valve or replace the entire separator assembly.
  • PLUMMER
    PLUMMER Member Posts: 42
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    Burnham installation manual

    The Burnham manual show a diagram of suggested boiler bypass and near boiler piping. Very easy and manufacturer recommended.



    Installer is the most important part of any system.
  • FWDixon
    FWDixon Member Posts: 78
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    Do you

    have a link for the RS-112 manual? All I can find is the RSA series....
  • Ironman
    Ironman Member Posts: 7,379
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    No Bypass

    Frank,

    Look at my reply on your other thread. It looks like an overhead gravity system to me. You don't want to put a bypass on that system; it will short circuit flow.



    Forget about modern piping diagrams unless you want to re-pipe the entire system.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • FWDixon
    FWDixon Member Posts: 78
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    OK

    will do....