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Check please on new boiler layout

1Ron_L1Ron_L Member Posts: 13
Hi all,
First thank you to Zman and Hot Rod for the input on my last question regarding the proper circulator for the reconfiguration of my radiant system. The radiant system has been in operation for 4 years and warms nicely. Now switching from a Phoenix Light Duty and HX on the closed side to a boiler and indirect. Long story but glad to be rid of that unit.

Zman sent me some homework and I figured the head and GPM for the individual zones and found that the entire system needs 8GPM and highest head was 9.1.(So I think). Did a recalculation of the heat loss using the Slant Fin program as others have suggested. Total BTU is 76K.

I have accumulated parts and ready to start putting things together but wanted your input on my diagram. All pumps are IFC and I have maintained the recommended straight pipe on all upstream runs to it. I do have a couple of questions also if you would be oblidging.

1. Are the air and dirt seperators in the right place. I usually see the air above the expansion tank but the Caleffi says closest to boiler outlet and low pressure area. Given the location of the expansion tank, I'm not sure if this primary loop is a low pressure area given that it is pumped hard with an 011 pump to achieve the recommendation for the boiler head/GPM of 22FT at 10 GPM

2. Speaking of the expansion tank. The circulator for the zones is pumping away from the tank but what about the primary loop. How does that fit in?? Is there somewhere else I should put it?

3. Not sure if any other check valves are needed. I thought that maybe a ballcheck valve on the supply to the indirect. I thought I remember that Hot Rod had mentioned something like that on another post to prevent any ghost flow from that circuit. Also should there be checks on the supply to the 2nd floor radiant zones. Returns have zone valves.

Any other suggestions would be welcome. Thanks again


  • ZmanZman Member Posts: 5,831
    Are you planning on domestic priority? With that piping scheme you would normally turn off the boiler circ in priority and size the indirect circ to move the water through the boiler and indirect. With the circs you have, you might be better off moving the indirect to the secondary and cycling the system pump off during DHW call.
    I am not saying what you have drawn will not work. It is a bit unorthodox and I don't have experience with it.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • 1Ron_L1Ron_L Member Posts: 13
    Thanks Zman. Did it this way because that’s what the HTP boiler manual shows.

    If I turned the boiler pump off and relied on only the indirect pump, wouldn’t I have to size that pump to overcome the high head restrictive boiler also. Another big pump? Could I just zone the indirect and use the boiler pump to do it all? I had the 008 SS from the previous setup so I figured why not use it.

    Is the indirect off the secondary the “normal” way to do this? Like I said, just following the HTP diagram.

    Have not thought too much about wiring. My service guy ( who has experience with these boilers) said we would wire DHW control right off the boiler or so I remember.
  • ZmanZman Member Posts: 5,831
    I have not worked with the newer HTP controls so someone more familiar may want to chime in.

    With Triangle Tube, Lochinvar and the older Munchkins, when you piped it like that, you sized the indirect circ for the additional head loss of the boiler and the boiler pump turns off under priority.

    You don't want to run the DHW as a zone because your radiant needs outdoor reset and the lower temps where the indirect does not.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • 1Ron_L1Ron_L Member Posts: 13
    Thanks Zman, makes sense about the zone setup. Will have to check again on that pump layout. Hopefully others can comment on setup I have drawn
  • Steve MinnichSteve Minnich Member Posts: 2,540
    I’m not sure if this has been mentioned but a Caleffi Sep4 would save you time and space, clean up the piping a lot.
    PHC News Columnist
    Minnich Hydronic Consulting & Design, LLC
    delta T
  • 1Ron_L1Ron_L Member Posts: 13
    Steve, I did see that after I had purchased the air and dirt seperators. Thought of bringing them back but then priced out the Sep4 and it would be almost $400 more so that buys a lot of pipes and fittings.
    Steve Minnich
  • 1Ron_L1Ron_L Member Posts: 13
    I appreciate the comments so far but can someone answer any of the 3 questions in my original post so I can move forward on the piping of the system?
  • Steve MinnichSteve Minnich Member Posts: 2,540
    I’d move the air separator so it’s piped in just before the system pump.

    Pipe in your water make up and expansion tank off the bottom tap of the air separator.

    Flow checks look ok.

    On your dhw, store the water at 140 degrees and use a mixing valve to mix down to 115-120 degrees.
    PHC News Columnist
    Minnich Hydronic Consulting & Design, LLC
  • hot_rodhot_rod Member Posts: 13,318
    I like the indirect piped at the boilers, before the secondary You get set directly from the boiler, no temperature mix A Z mentioned that circ needs to be sized for the indirect, boiler, piping and valves in the circuit Needs to be at least the same as the boiler circ spec
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • 1Ron_L1Ron_L Member Posts: 13
    Ok, so I thought I had my head wrapped around this but now I'm confused ( not hard to do).

    First off, question for Steve or anyone else who would like to comment. What is the reason for moving the air seperator? Caleffi always notes that it should be closest to the boiler because that is where most of the air is released and can be eliminated. Doesn't moving it away prevent any air in the primary and DHW loops to be scrubbed away? Also the pressure tank is close to the intake on the radiant system pump now so doesn't that work as "pumping away"? I do see the air eliminator above the expansion tank often but is that just for convenience because that is where cold water enters and cold water doesn't release air as well as hot (granted, not much make up water should be entering after the original fill).

    Secondly, regarding Hot Rod's comment. I will pipe the indirect as shown because that is what HTP shows but the pumping is not as I thought. Sounds like only the DHW pump will be running in this configuration and not the boiler pump also, so that is the need for the DHW pump to be as large as the boiler pump to accomodate the boiler head loss and GPM. Zman was kind enough to previously plot my Elite requirements on a pump graph ( See attached) and it looks like only the 011 pump would fill those shoes. Does that mean that I would need 2 of these 011 pumps?? One on the boiler and one on the indirect?? Seems like two large pumps.

    My original understanding was that the boiler pump would run in conjunction with the indirect pump ( refer to the Taco wiring PDF) thus allowing a smaller indirect pump to be used. In the diagram, the system pump would be the boiler 011 pump, the secondary pump would be the VR1816 feeding the radiant and the DHW pump the 008 on priority. Does that not work? My only thought was that if the boiler pump and the indirect pump worked at the same time, there might be conflict because they are not hydrolicly seperated. If run this way, is it that the DHW on priority will not be hot enough and be subject to the outdoor reset as Zman mentioned earlier?

    Please help my confused mind!
  • 1Ron_L1Ron_L Member Posts: 13
    Figured I would bump this to see if there are anymore comments before I start piping this weekend
  • Steve MinnichSteve Minnich Member Posts: 2,540
    As far as the AS goes, I put an air vent at the top of the boiler like a Spirovent Jr. or a Taco HyVent. There’s a lot more water flowing through the system side of the P/S piping that you’ve sketched. More water, more opportunity to remove air.

    If the DHW pump is piped in parallel to the boiler pump as you’ve plotted, there’s no need to have the boiler pump running on a strictly DHW call.

    I’m not familiar with the control strategy of the HTP boilers. I was mostly a Lochinvar and Burnham guy.
    PHC News Columnist
    Minnich Hydronic Consulting & Design, LLC
  • 1Ron_L1Ron_L Member Posts: 13
    edited August 2019
    Thanks Steve, that’s helpful and I appreciate your time and comments. It makes sense about the amount of water passing through the system but the way I’m seeing it, anytime the water moves through the system side, it also goes through the boiler and through the AS too and at that time hotter and more ability to give off more air if placed where I have it near the boiler.

    Looks like if the DHW pump runs alone on a call, i’m gonna have to
    pick up a larger pump as others have mentioned to compensate for the head loss flowing through the boiler. Damn, thought I was going to be able to use most of what I had from the previous iteration
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