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Re-piping existing boiler

DJDrewDJDrew Member Posts: 52
edited September 3 in THE MAIN WALL

I was wondering if I could get some opinions on the best way to move forward with a re-pipe. Currently we are pumping into the expansion tank and experiencing some odd issues at upstairs radiators and collecting air - especially ones near the end of the lines. After reading Dan's book, I think some of this is likely attributed to pumping into the expansion tank.

Based on what I read, it seems I have two viable options for re-piping. I am trying to address this in the simplest way possible. Attached is a picture of the existing setup and then two options I sketched out.

Option A: I think this would move to a primary-secondary arrangement. While I'd save costs on piping, I'd have to spend money (and electricity) on a second circulator. This option is appealing as all radiators will get the full power of the circulator, regardless of what the ESBE is doing.

Option B: I think this switches the existing setup to "Pumping Away" but the ESBE would still throttle the entire system for awhile?

Does anyone have any thoughts or suggestions on the preferred way to repipe? It is going to cost a few bucks to do, so I'd like to try and get it done and done right.


  • mattmia2mattmia2 Member Posts: 1,740
    I wouldn't worry a lot about the proportion of circulation that goes through the mixing valve vs the system, it doesn't take much flow in the system to move the heat. As long as the flow in the system is balanced to the load, it will heat proportionally regardless of what the flow is from the proportioning valve. If the system isn't designed very well and relies on brute force to sort of work then maybe you should thing of p/s or adding some way to balance it.

    Get a good microbubble scrubber type of air separator.

  • SuperTechSuperTech Member Posts: 1,390
    Need a little more info on the boiler, existing piping and the issues you are experiencing.  What type of boiler do you have and how old is it? Is the boiler just for space heating or does it also take care of domestic hot water? Just one zone? Do you have only one air vent?

    Going to a primary secondary setup might not be necessary.  I would absolutely recommend pumping away and using a micobubble resorber air eliminator. Your issues could be from a bad air vent and incomplete purging of the zone and bleeding of the radiators.
  • Jamie HallJamie Hall Member Posts: 13,209
    And while you're at it, I have to wonder -- if you are getting air in the upstairs radiators... what pressure is the system running at, hot and cold?
    Br. Jamie, osb

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

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • DJDrewDJDrew Member Posts: 52
    edited September 3
    All, thank you for the feedback. Here are some answers to your questions:

    Age/Boiler: 2017 Slant/Fin Sentinel SE105. The boiler is only for space heating. The setup is a giant single zone, essentially Front/Rear of house T's above the boiler and drops down.

    PSI: Cold is a little over 12psi. Hot ends up a little over 15psi.

    Typical operating temp: 130-135. Only on design days after an hour of running will it get up to the low 140s. (Old gravity system, house over radiated.)

    Air Separator: Currently the one installed is a SpiroVent.

    Aside from air issues settling at end rads of the system, sometimes we can hear what sounds like a gurgle of air in the water go through the pipes once the system shuts off. The only other really annoying issue we have is that the rads at the end of the line heatup last, even if we close all the radiator valves down to a minimum earlier on, it seems there is just not enough flow to the ends with the current setup unless the boiler runs a long time.

    You can see pictures of this system in an earlier thread when I was advised to add protection to keep the return temperature higher.

  • DJDrewDJDrew Member Posts: 52
    All thanks for the feedback, I will be reaching out to local vendors, asking for option b to implemented.
  • hot_rodhot_rod Member Posts: 13,738
    Could be the cast iron radiators have air bubbles trapped up top. Are there bleeder screws on each radiator?
    Two things, they can be noisy, and they can also act as a false PONPC
    You need at least 2 feet per second velocity to push air through then pipes. With large pipe conversions you may not have enough flow. try increasing pump speed.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
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