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Burnham ES2 low return water temperature

jeremy0
jeremy0 Member Posts: 3
edited March 2023 in THE MAIN WALL
Hi Folks!

I had a Burnham ES2 boiler installed about a month ago. The system has cast iron radiators (original gravity system, still uses 2" pipes), radiant floor (under wood/tile), fin-tube (one of which is a microzone), and an indirect.

Unfortunately, it wasn't installed with a bypass or any low return temperature water protection, and with the radiant/old gravity system, it runs for a long time with really low return temperatures. The CI radiator zone might get the boiler supply temperature up to 130°F before shutting off after ~20 minutes, so we have condensation that doesn't get sent up the chimney.

I'd like to add low return water temperature protection so this new boiler doesn't rust away like the old one did. In the docs that came with the boiler, Burnham recommends their bypass kit (107795-01) - variable speed pump with a temperature sensor as a system bypass, but it's on backorder everywhere.

Anyone have any idea where I could find this in stock or are there any alternative options that could take the place of their bypass kit? I definitely want to stop this before it becomes a bigger problem, so I'm open to ideas. Thanks!






Comments

  • hot_rod
    hot_rod Member Posts: 22,121
    edited March 2023
    Don’t bother with that bypass kit, it will not do what you think it will. Image 70 return from the radiators, boiler supplying under 130F for 20 minutes. How does that pump increase the return. It doesn’t, can’t won’t

    Buy a VS set point circ and one of these two piping. I added a buffer on one drawing to help that small radiant zone to not short cycle the boiler.

    In these drawings the vs circ becomes your “thermal clutch”. Via the wonders of primary secondary piping the boiler disconnects from the load, until the boiler catches up.

    The VS circ allows only the gpm the boiler can provide while staying above 130 return. So you will always get some amount to the radiators, 100% flow when return sees 130

    100% absolute protection. Possibly less $$ also. Any circ operated by a tekmar vs control would work.

    But some piping changes required.

    If it were zone valves with a single circ, a simple thermostatic valve could have been installed. And eliminated about 500W of circulators
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • MikeAmann
    MikeAmann Member Posts: 997
    Nice setup. Very well laid out.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,830
    And using Hot Rod's re-pipe you can keep it nice by moving the boiler away from the wall 18" to 24" and extend the gas pipe and vent pipe. That way you can tuck the buffer tank behind the boiler. If you don't want to mess with moving the boiler, you may just place the buffer tank next to the boiler and just re-do the boiler piping to the tank next to the boiler instead of behind the boiler.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • hot_rod
    hot_rod Member Posts: 22,121
    edited March 2023
    I think a 2 pipe buffer may work, off the shelf stubby 30 electric DHW tank, 30" tall. Remove dip tube connect two top ports. Bottom element hole with 1" M X 1-1/4 copper adapter.
    Boiler on a tight ODR maybe 150 or 160- 180°

    Any PSC circ with the tekmar VS setpoint control
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • The Steam Whisperer
    The Steam Whisperer Member Posts: 1,215
    hot_rod said:

    Don’t bother with that bypass kit, it will not do what you think it will. Image 70 return from the radiators, boiler supplying under 130F for 20 minutes. How does that pump increase the return. It doesn’t, can’t won’t

    Buy a VS set point circ and one of these two piping. I added a buffer on one drawing to help that small radiant zone to not short cycle the boiler.

    In these drawings the vs circ becomes your “thermal clutch”. Via the wonders of primary secondary piping the boiler disconnects from the load, until the boiler catches up.

    The VS circ allows only the gpm the boiler can provide while staying above 130 return. So you will always get some amount to the radiators, 100% flow when return sees 130

    100% absolute protection. Possibly less $$ also. Any circ operated by a tekmar vs control would work.

    But some piping changes required.

    If it were zone valves with a single circ, a simple thermostatic valve could have been installed. And eliminated about 500W of circulators

    The bypass pump will likely reduce the flow through the boiler down to 1Gpm or less when its 70F return., which is not a problem. Its not just temperature that matters, but the flow rate, especially with higher mass cast iron boiler ( won't work on low mass boilers like a copper tube). Thaat's how bypass piping works ( which is essentially what this pump set up its doing). If return temperature was the only criteria that needed to be met, nearly all two pipe steam boilers would be condensing nearly constantly since the return water is typically near room temperature much if not all winter. However, since steam systems only have to move about 1/50th the amount of water for the same btu output, return flow rates are quite low.
    To learn more about this professional, click here to visit their ad in Find A Contractor.
    Mad Dog_2
  • hot_rod
    hot_rod Member Posts: 22,121
    on paper it looks this simple.

    Don't waste time with bypass piping, or pumping. To make it work an additional vs pump properly applied, is worth the cost.

    An adjusted bypass only work at the specific time it is set. With 7 zones it gets complicated.

    Buffer is optional if that small zone calls often by itself.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • jeremy0
    jeremy0 Member Posts: 3
    edited March 2023
    The VS primary/secondary layout makes much more sense to me... I couldn't make sense of how the system bypass could work with a large temperature difference.

    I love the simplicity in using something like a Taco VT2218 instead of a separate controller, but is it powerful enough to provide enough flow? I calculated that I need 13 gpm (for delta T of 20 and 130,000 btu/hr - I think 130k is the right number, but I've added a picture of the boiler label), which I think should be fine with the 1.25" pipe, but can both loops and injection piping be the same size? I take it I'd also need to add a mag filter if I go with an ECM pump like this, right?



    For ODR, would it be better to handle this in the boiler's aquastat or separate injection mixing controller (with PSC/non-ECM circulator)? The boiler does not have the ODR IQ card currently, so I'd have to get one if I don't want to use an external controller for ODR.

    I like the idea of a buffer tank, it's something I've been thinking about since got the new boiler installed. Would a 20 gallon tank be big enough though? Rough estimate with a 5000 btu/hr load and only 5 minute run time:



    Does the buffer tank replace the 2nd set of closely spaced tees?
  • hot_rod
    hot_rod Member Posts: 22,121
    Too bad the folks putting out that module and drawing don't understand the "math":0 Some expensive lessons will be learned. Maybe a visual with some actual numbers will help with the concept of VS pump temperature protection, see below.

    $$ is about the same buying a circ and separate control, or a circ with it onboard. If you want a specific size circ, the tekmar control might be a better option.

    Buffering a small load with a fixed output boiler gets into a large tank. A 30, 40, 50 are usually the least expensive tanks. I doubt a 20 is worth the effort? How often is that smallest zone to only one operating? Here is the correct formula for tank sizing. Call it a 130K boiler with a 5K load, 10 minute time.

    The ODR card is probably the least expensive option.

    Does the system ever need the full 130K that boiler can offer? In not that circ could be fine with 10- 12 gpm, maybe. If the load is 100K or less, all 1" copper.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • jeremy0
    jeremy0 Member Posts: 3
    edited March 2023
    The small zone is on and off by itself a lot throughout the day. That room isn't insulated very well. This might explain why it previously was wired up in a way that the thermostat would start the circ but never the boiler (it would just use residual heat left in the bpiler over from other zones). According to that formula, I'd need a 125 gal buffer tank. Definitely need to think a bit about that one before deciding if I want to go down that path.

    We need about 110 k BTU on design day, so 100k may not cut it a few days a year. Plus, the indirect is on the manifold as well. I read in one of the tekmar docs that it should be a size smaller than the boiler/system loops, but wasn't sure if that matters for this application of mixing. Might need to do some more repiping if this won't work
  • EricPeterson
    EricPeterson Member Posts: 215
    hot_rod said:



    If it were zone valves with a single circ, a simple thermostatic valve could have been installed. And eliminated about 500W of circulators

    My favorite topic.

    "If it were zone valves with a single circ, a simple thermostatic valve could have been installed" - @hot_rod do you have a diagram for his layout?

    Thanks,
    Eric Peterson
  • hot_rod
    hot_rod Member Posts: 22,121
    Here is the info o0n the Caleffi 280 thermostatic protection valve.

    https://www.caleffi.com/sites/default/files/file/01223-23_na.pdf

    Some application schematics here. Its a valve we sell to the solid fuel boiler industry in Europe mainly. Available in the US and Canada also.

    https://www.caleffi.com/sites/default/files/coll_attach_file/idronics_10_0.pdf
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • EricPeterson
    EricPeterson Member Posts: 215
    @hot_rod - thanks, but those diagrams are overly complicated for my setup which is a converted gravity system, one circulator, and three zone valves.
    I've read that there aren't many converted gravity systems out there, which seems kind of surprising to me. Regardless, I would think there would be a simple module for providing protection to the boiler against low-temperature return water.
    Burnham seems to be trying to provide this with their kit, but it does not seem to do the job very well, which is even more surprising, since they are a big company with presumably lots of design talent.
    All I am looking for in my case is a simple layout with a thermostatic bypass that provides the proper protection. It seems to me that such a layout would apply to 99% of converted gravity systems.

    Thanks,
    Eric Peterson
  • hot_rod
    hot_rod Member Posts: 22,121
    edited March 2023
    This is pretty simple, bypass pipe and 3 way thermostatic.
    It doesn’t fix the short cycle issue of that 5 k zone however.

    This goes to my point of a mod con being a better match for a zoned system regardless that it needs 180 for a portion of the season

    Run your actual numbers with a mod con and that low load zone, the buffer is much more realistic.

    Or add that small zone to a larger zone thermostat call. But that defeats one of the nicest attributes of hydronics, zone-ability
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • OldawgBryant
    OldawgBryant Member Posts: 69
    @EricPeterson I'm in that same "minority" of converted gravity and I'm replacing the original boiler. Did you ever find a solution for the bypass? I was also looking at Burnham's pump. I could have had my 97 year old Bryant go farther but the condensation got it...
  • EricPeterson
    EricPeterson Member Posts: 215
    edited September 2023
    @OldawgBryant - I decided to go with the Caleffi 280 Series ThermoProtec thermostatic mixing valve.
    I am in the process of installing it now and hope to wrap it up in the next few days.

    Now the valve shows up in ads everywhere....




    Eric Peterson