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Constant Circulation

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jwade55_3
jwade55_3 Member Posts: 166
Thanks,

I could move the primary circulator to the return, my real questions are on the secondary side of the piping, not that I don't valve and appreciate the input.

Thanks

J

Comments

  • jwade55_3
    jwade55_3 Member Posts: 166
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    Been working on ideas for

    constant circulation with Modcon boilers. I'm thinking about repiping my muncher per the attached drawing. More than anything for research. Control sequence would be, zone pumps run below 60 OAT, zone valves open to maintain a floor temp, with space temp hi limit. Boiler temp reset by vision 1. Amy ideas, changes, etc..

    Thanks,

    J
  • Constantin
    Constantin Member Posts: 3,796
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    Are you going to get enough flow?

    IIRC, the Munchkin HX is fairly particular about the flows it needs to see in order to be happy, hence the I&O manual preference for pri-sec piping, I guess. Have you considered how much flow you'll develop at either end of the firing range and how that'll interact with the system?
  • jwade55_3
    jwade55_3 Member Posts: 166
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    Constantin,


    First, I'm glad to see you adding your expertise to our industry. As to the flow, the DPBV should take care of that for me, I've run the numbers, but don't have them in front of me right now.

    Thanks,

    J
  • Paul Pollets
    Paul Pollets Member Posts: 3,656
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    Pipe sketch

    The Vision1 book has the preferred pipe schematics and P1 pump location pumping from the return through the boiler to maintain required flow. Near boiler piping must be 11/4".

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  • jwade55_3
    jwade55_3 Member Posts: 166
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    Another idea

    Another view of a piping possibility.

    J
  • Paul Rohrs_4
    Paul Rohrs_4 Member Posts: 466
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    Nice drawing.

    I agree with Paul on the boiler pump location, I would expand on that with a dedicated boiler loop and primary loop. Nice work though. I like the 2nd drawing, but I think zone valves might be overkill.

    Regards,

    PR

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  • jwade55_3
    jwade55_3 Member Posts: 166
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    Thanks Paul(s)

    What I'm thinking is how to keep circulation, without overheating individual zones? I've done many Minitube systems with injection, trying to pare it down to small residential, with condensing boiler.

    J

    Paul Rohrs I think we may have shared vision stencils before?
  • Wayco Wayne_2
    Wayco Wayne_2 Member Posts: 2,479
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    They both look

    good to me. I like the constant circulation idea. I like the first picture best because it is simplest. If you size the circ and adjust the bypass right you don't really need the extra circ. (Yeah I'm Scottish. Thrifty to a fault) Are all zones the same temperature. If not you could go primary secondary and prioritize them from hottest to coolest and not even need the bypass. (Cave man hydronics. Place a stone in your campfire and place it under your chair cushion) :o WW

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  • jwade55_3
    jwade55_3 Member Posts: 166
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    Yeah that was my thinking on the first one, KISS. I ultimately want to come up with a simple/efficient/non-cost prohibitive constant circulation layout for our designs. In this case all zones are the same temp, could add a thermostatic valve to a lower temp zone, see attached, say a slab. I like the pri-sec idea, but cannot get my mind around how to isolate the heat input from the zones, ideas?

    J
  • Alex Giacomuzzi
    Alex Giacomuzzi Member Posts: 81
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    Interesting....

    Hi J:

    I prefer the 2nd flow schematic if you are looking at having constant circulation without a flow thru with the boiler that is.. It also offers you a bit more functionality...

    I tend to concur with Paul and Wayco above......... the solenoid valves appear to be an extra unless you must absolutely have 100% shut off capability which you could possibly do without. In fact the PRV would not or should not be required if this were piped as a secondary with 2 closely spaced T's and the appropriate flo check valves and leaving the solenoids out.

    With the solenoids incl you need a PRV with the piping shown, without them you do not or possibly not....see below...

    Now you were concerned about overheating an area....
    If you are not supplying any additional heat from the boiler, the best you can do is move heat around within the system with a pump running. That movement it really quite gradual and should not cause any overheating so to speak unless you have some great solar to capture and distrubute... If you are purely in a constant circ mode, you could have all the zone pumps running ---- if that is what you desire along with your primary loop pump. That is a lot of pumps running........
    When a call for heat comes in, only that zone pump would run ---- the others would stop. After the call was satisfied, the others could start. I have an idea..

    Another thought....... Scrambling things a little bit possibly but pointed at constant circulation..in particular.... Let's try this approach.

    Assume you have your primary loop set up as in figure 2.
    Your individual zones would be piped slightly differently than you presently have them shown....
    They go from the supply header and would have a solenoid valve followed by the heating loop back to the return header....... This could be to most simple variety of piping loop. A slightly more complex variety could have a pump between the solenoid and the heating loop for example if the loop design required more heat pressure.

    The primary circulator would be sized appropriately and if added head was required a pump could be located between the loop solenoid valve and the heating loop. Similar amount of hardware that you have shown only configured slightly differently...

    The controls would be---- when there were no heat calls "ONLY" the primary circulator would run and all solenoids would be open, but only the primary circulator would run, not the other pumps (if installed). The primary circulator will pump thru enough for constant circ.. Now if a call for heat comes in, the other solenoids close and just that one zone enjoys the call for heat. If there is an additional pump in that zone --- it turns on with the call and appropriately off when the call ends....

    When the call is over.......the other zone solenoid valves open up and the total system is back to constant circulation... with only one pump running..the primary circulator pump.

    Regards Alex










  • jwade55_3
    jwade55_3 Member Posts: 166
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    Alex,

    Sounds interesting, can you do a sketch of what you are describing?

    Also my thoughts are that I would like circulation to continue within a zone, even when there is a call for heat to another.

    Thanks,


    J
  • hr
    hr Member Posts: 6,106
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    What about 3 way zone valves

    Here is an idea I had. Although not yet implemented :)

    Gives you constant circ, a decoupler for the boiler, air purger, and a nice, easily mountable insulated PS piping "box".

    More ideas at this link

    http://www.pmmag.com/CDA/Archives/4073b3e8510d7010VgnVCM100000f932a8c0____

    hot rod

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  • Uni R
    Uni R Member Posts: 663
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    Sweet!!! n/m

  • jwade55_3
    jwade55_3 Member Posts: 166
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    That's what I'm talking about.

    That is a great idea, easily applied to existing systems, and existing mindsets.

    Thanks everyone.

    J
  • jwade55_3
    jwade55_3 Member Posts: 166
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    That's what I'm talking about.

    That is a great idea, easily applied to existing systems, and existing mindsets.

    Thanks everyone.

    J
  • hr
    hr Member Posts: 6,106
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    If you are in a 3 way state of

    mind... May as well handle the indirect with one also. Saves a circ.

    Caleffi has a 1" 3 way with an 8 cV and a 20 psi close off. Plenty of flow for DHW recovery.

    hot rod

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  • jwade55_3
    jwade55_3 Member Posts: 166
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    Another good idea.

    Only drawback I see is larger circulator required, with pressure drop of boiler, indirect, three way( even with generous CV), piping, etc. But I guess a larger is required for priority DWH anyways, Hmmmmm something to think about. I'm also concerned with over-pumping boiler on heat only call, throttling valve in primary tie in. I'm working on a design for a guy that will try anything I come up with, once :) I may propose these ideas tomorrow.

    J
  • hr
    hr Member Posts: 6,106
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    Depends on the boiler choice

    More and more of the Mod-Con's are getting ported out HXers.

    The Lochinvar Knight runs a Grundfos 15-58 all the way up to the 210K model. I think the Prestige runs with a low head as well as the new Slant Fin and a few others.

    Unless you have a real restrictive coil in the indirect you shold be fine with a high Cv zone valve. Most of the manuals show the available head in their installation instructions.

    I like the Phase 3 or Weil tank in tank design for this. The pressure drop in that is nil. Same for the Ergomax style tank.

    Sounds like the new Lochinvar indirects have a large diameter, wide open coil also.

    hot rod

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  • jwade55_3
    jwade55_3 Member Posts: 166
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    Interesting.

    I just pulled out the lochnivar install manual, seems they are using 40 deg delta as their circulator sizing default, I guess that explains the 1" boiler tapping, nice. Take a a standard approach, 20 deg delta, WOW, guess thats the dual HX's. It's tough to get people to think about sizing pipe based on flow requirement, instead of device tapping size. You are again dead on with the tank in tank, and lower pressure drop boilers, I'm working with what I've got to go to market with, like my dad says, "work with what you're given"

    J
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