boiler, buffer, backup, DHW and loads

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Bob Rohr, Mar 2, 2013.

  1. Blue Tornado

    Blue Tornado
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    WOW... Wild looking control room there.

    I am thinking that this diagram is doable with the bumblebees. Not the most economical way to go but still seems to me it is workable.

    Both pumps wired to go on from boiler controller at 180 or so. Notice sensor locations as per Taco install sheet.
    Hope the upload goes well enough.

    Boiler Protection.jpg
     

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  2. __dan

    __dan
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    Yep, thought you guys would like that. The crowd here keeps asking how to wire circs with extension cords. Looking at the bumblebee documentation, page 5:

    http://s3.pexsupply.com/product_files/Taco - HEC-2 - Install Instructions.pdf

    shows *this* ECM circ is a single thermistor control. So, for the P1 system circ it will vary pumping to maintain setpoint boiler return temp. However, as the P2 variable speed storage charging circ, this unit does not incorporate boiler return temp protection and could easily overpower the P1 system circ, driving low temp storage water into the boiler return. The ECM VS storage injection pump would need two thermistors minimum to do setpoint VS injection pumping with boiler return protection, ramping up load only as allowed by keeping boiler return water temp, BRWT, above setpoint.
     
  3. Blue Tornado

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    It would seem to me that the P1 would also ramp up to meet its setpoint as P2 ramps up. They are equal pumps. Just my thoughts without experience in this field, yet.
     
  4. __dan

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    If the system has been running (boiler firing) 2+ hours with hot storage, loads returning hot, yes. In the first hour or two with cold storage and initial demand at max, the boiler could be struggling and get hit at the return with 90 to 100 deg water in volume from storage. As shown, with no P2 boiler return protection, P2 will initially go to full speed, ramping max up to the setpoint of its sensor (sensing temp below setpoint). Because it is sensing max load. P2 is supposed to stay off until *a* BRWT sensor enables P2, then P2 is supposed to ramp slowly up, limited by the BWRT sensor staying above the low limit protective setpoint. As the BWRT increases, P2 may increase, sending more to the load and more return to the boiler. It is cold start protection. The bumblebee HEC 2 does not have this functionality, but I'm sure an ECM pump with integral BWRT protection will come to market. I'm going to check the specs of the Grundfoss Alfa.

    In setpoint mode with the sensor at the boiler return, P1 will actually slow as the return becomes hotter and less supply mix tempering is required
     
  5. Floydian

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    I sure do love my lk810 loading unit, despite the cost. Isolation ball valves, unions, temp gauges, insulation package all in one. Pretty simple.

    And it shouldn't be too long before we see ECM pumps on loading units as an option on this side of the pond. The lk810 eco has a 3 speed Alpha(50 Hz).

    Fewer pumps and less power usage sound good to me.

    Noah
     
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  6. __dan

    __dan
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    Drawing is very close to my as built but it is closer to my idea of a reference design. I don't know if I will get enough heat passively from the storage as shown but I do know I get enough straight from the Froling supply header, when the Froling is firing. I have a circ there and disabled it, I do not have to pump through, plenty heat rises.

    Primary concerns, fast heat from repeated cold starts bypassing storage at startup. Direct isolated, and heat trapped loops do not heat up idle piping. Mod con boiler would have OAT reset and DHW priority call built into the boiler, so, taps directly into the loads. Using OAT reset built in the mod con boiler and bypassing storage increases efficiency, lowers RWT, boiler firing turns down and goes off earlier every firing cycle.

    Drawing shows the LK 810 loading unit which will close off flow to the boiler as return temp drop below 150 F or so, reducing boiler standby loss while drawing from storage (but I could redraw it to show the BWRT protection built into the pump controllers).

    Tried to show a hydraulically separated flow between DHW and storage to maintain stratification, DHW has a high flow and high return water temp while storage would want to come off and return slowly. Since electrical is my thing and not heat, this last part is the one I would like heat engineered (can I take heat from storage slowly and passively as shown?). Indirect over plate and frame because water soluble minerals in the cold water supply, when heated will cause mineral precipitation either in the tank or on the HX plates. Low grade service techs in the future will cut and replace the plate and frame HX rather than clean it, just like they will chop the ECM circs and replace with old style PSC. Codes and reference designs will have to change to make a market in this.

    Lastly, This is the only thing I would consider when building new (in cold climates). Found the link in another thread here. Insulated envelope totally surrounding the foundation, Heat that radiantly and there's most of your storage and distribution problems solved, very simply.

    http://www.nauglerhouse.com/foundation.html

    Fresh drawing in the last hour for your viewing pleasure.

    froling as built.JPG heat and DHW.JPG
     
  7. Willman

    Willman
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    Can't comment on the control or electrical end of your install but wonder how the long length of horizontal smoke pipe works out? Any ash issues?
     
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