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Opinions on system design (s milne)

J.C.A._3 Member Posts: 2,981
As far as I know, there are all high temp emitters on this job. Plan includes using zone valves for individual zone control, and possibly a panel distribution system like ZCP...(hopefully! our first. )

I'm thinking a pressure differential by-pass, and a staging control based on boiler return temps with an outdoor re-set for those not so warm days.Maybe later, a water maker add-on. H.R., we ARE pretty much forced to use the chimney for venting, and that has been one of the major thoughts.DV or power venting will not fall within the realm of perhapsibility on this job.

11 zones, I think, plus thinking forward, an indirect water maker for 5 apartments and 1 business, a toy and card shop in the basement.Currently a 50 gallon gas fired hot water unit, with no complaints.

Just clarifying the thoughts.....Chris


  • ScottMP
    ScottMP Member Posts: 5,884
    Hey guys

    I am quoting a system in which I will have two smaller boilers for an apt. building. I really like the idea of two smaller boilers for redundancy and for better control of the building load. These two boilers will be controled with a tekmar staging control.

    There is more than one way to skin a cat and I wonder what your thoughts are on the following three designs.

    What would you use and why ?



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  • hr
    hr Member Posts: 6,106
    Condensing boilers?

    more than one temperature? Micro zoning? Indirect? I would like to know a little more about the big picture before I weigh in :)

    hot rod

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  • bigugh_4
    bigugh_4 Member Posts: 406
    Your cool!

    I looked at the Caleffi description of their unit and your statement is the correct answer. If the system is just a straight forward single type of emitters, why spend the $$$, But if the emitters are varied and of different flows, the Hydronic Seperator is a neat answer.
  • Constantin
    Constantin Member Posts: 3,796
    I'm still learning about all this...

    ... so please bear with me.

    Wouldn't it depend a bit on the fuel and the type of boiler? For example, the Caleffi approach could be ideal for applications where you have a high-head HX like a Vitodens, Munchkin, etc. right? The LLH makes piping the rest of the system a bit easier...

    Whereas the two following designs are best suited for non-condensing boilers that need flue gas condensation protection? If you have a low-head HX and low-mass condensing, modulating boiler on your hands, why not simply make it part of the primary circuit?

    Of the two, I like the combined Pri-Sec better as it presents both boilers with the same incoming water temperature. That makes staging them easier, right?
  • Ted_9
    Ted_9 Member Posts: 1,718
    Cast iron?

    So they are cast iron boilers then.

    Five apartments and stores? Lets push that air out.

    I would not invest the extra money in the Caleffi approach(not for this job). Keep it simple. Forget the last option. Go for the combined P/S and put the circs on the supply side. Then you will have a circ to circulate the primary loop controlled by the Tekmar, right?

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  • S Milne
    S Milne Member Posts: 112
    Hot Rod

    These will be atmospheric cast iron boilers with what I would consider a few micro zones. Copper finned tubing in most Apt.s

  • S Davis
    S Davis Member Posts: 491

    How large is the flue, any offsets?
    We have run PVC venting up through an existing flue and where able to install condencers, on one job we got four 3" PVC vents in a larger flue.

    S Davis

    Apex Radiant Heating
  • Andrew Hagen (ALH)
    Andrew Hagen (ALH) Member Posts: 165
    I like

    the one that uses the Caleffi Hydro Separator. It vents both sides of the system. Of course you don't need it for hydraulic separation, but you do need it for thermal separation. Makes no difference where the boiler pumps are in that application. You can pipe the expansion tank into the bottom of the Caleffi unit. I like to minimize the number of circulators and use zone valves with a dP bypass. It might not be as inexpensive as close tees, but I like the way it organizes the piping, venting, and thermal expansion in one unit.

  • hr
    hr Member Posts: 6,106
    11 zones

    all split and controlled at the boiler location? I would use that "ladder looking" parallel primary loop approch, so all zones get the exact same temperature.(Chapter 11, page 445 of the 2nd edition of Modern Hydronic Heatings)

    What is the total load, and or the load of the various zones?

    With cast iron boilers, and a one temperature system, really no need for a hydraulic seperator, unless you like to embrace technology to the fullest :)

    hot rod

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  • Floyd
    Floyd Member Posts: 429
    I'm wondering?????

    Y no use of the chimney???? If you got enough chimeny to vent two good ole atomo boilers then you got to be able to get fresh air in there and you defintely got enough room to run two 3" PVC pipes up the flue.... who says you got to pull air from the outside???? On further reveiw you will probably find you do have enough room for four pipes.....I have an install with four WM GV's that have the S/S run up the old flue and they pull intake from the room and the vent that supplied the old beasty that I hauled up out of there in card board boxes full of CI galss wool and fire brick all broken up by my hands on the handle of the BFH.........
    The GV's have run flawlessly for 6 years now, maybe 7, time flies.... espec. when you can install something and forgetaboutit.....
    I'd be figgering away to get some kind of condenser in there, be it a big V, GB, Munchie, or Ultra, something or other and then hook it up with option #2.....I'd be pretty leary of all those zone valves though.....I like good circulation... nothing makes a system work better than good circulation. Too many zones to one pump and wham-o you's gots big problem's and your scratchin' you behind tryin' to figger out Y....

  • ScottMP
    ScottMP Member Posts: 5,884

    Its also ALOT of flow when all zones are calling !


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  • Dave Yates (PAH)
    Dave Yates (PAH) Member Posts: 2,162
    ZCP the way to go

    Mornin Scott,

    I'm a fan of the panelized approach with the primary pump included in the panels. The by-pass and indirect zone can also be included so that your twin boiler install can be kept simple, clean and appealing to the consumer. The only thing I'd add for cast iron boilers, would be a system or boiler by-pass in 3/4", which is a nice-to-have feature.

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  • tim smith
    tim smith Member Posts: 2,738
    dual boilers, primary secondary.

    We are doing one right now with duals. Your 3rd drawing is how we are doing it except pumps on the supply's. Tim.
  • hydronicsmike
    hydronicsmike Member Posts: 855
    Scott - Boiler Piping

    Hello Scott,

    My favorite is the drawing in the middle, the "combined Primary/Secondary.

    Piping it this way is probably cheaper than using the Caleffi sperator or any low loss header and achieves much of the same thing, resulting in lowest stand-by losses.

    Please feel free to call me at 250-545-7749, Ext. 214, should I be able to help with anything. Have you looked at tN4??


  • ScottMP
    ScottMP Member Posts: 5,884
    Ah Yes ZCP

    IS just what I wanted to do but I am trying to watch the cost.

    I know the cost of install shoild be lower by using the ZCP correct ?

    Thanks Dave


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  • ScottMP
    ScottMP Member Posts: 5,884

    That was going to be my original design but my concern is that when the second boiler kicks in it will see the supply temp of the first boiler and not have a true reading of system return temp ..


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  • Ron Schroeder_3
    Ron Schroeder_3 Member Posts: 254
    Why cast iron?

    Hello. Forgive my obvious self serviance but, why do the boilers have to be cast iron? Is your client only concerned with the initial capital cost of the repower? Did he/she unequivocably communicate that operating and life cycle cost do not matter? Just wondering...
  • Carl PE
    Carl PE Member Posts: 203
    I use..

    Design #2, for exactly the reasons you mentioned.
  • Floyd
    Floyd Member Posts: 429

    But if you go condensers you have to have the piping for a ton of flow in the P/S header anyway, so what the h...... do it and you won't be sorry. Nothing worse than listening to pissing and moaning because you tried to cut a corner and worse yet when you really knew better.
    Do it right and do it once....

  • ScottMP
    ScottMP Member Posts: 5,884
    Yes but ..

    IF we do P/S we only need one pump large enough to keep the proper flow thru the boiler, not eleven.

    I am not trying to cut corners Flyod, just trying to design a proper system for my customer. By pissing and moaning I assume you refer to the Taco zone valve problems of the early seventies ? I do know better and have come to realize that zone valves actually work now in the year 2005 and can lower electric consumption and use less space. The only advantage I can see to useing all those pumps would be that they are self balancing.


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  • Floyd
    Floyd Member Posts: 429
    you got it....

    I think that self balancing is a wonderful thing.... you don't have to worry about the shortest loop always getting satisfied first... the pissing and moaning I'm refering too, is from the HO when the single pump goes and the whole house gets cold, rather than just one zone. Or the grief you will get when they come back from Vac. and had the heat turned back to 50 and then call you wondering why all the zones aren't heating when then turn the heat up, Of course that will be around midnite, when your more interested in talking sweet to your wife then babysitting some miserable HO.......
    Then there's the issue of elec., do you really think the HO gives a rat's behind about electric when he goes out and buys the entertainment system with the highest watt amp that he can possibly find so that he can rattle the crap out of his windows????? Why should you worry about a couple of amps???? besides all the pump are not going to be running all the time and the single one will.... and if you can install a condenser instead of an old atmo. CI. job the gas you save will easily pay for the extra electric.....
    Plus most HO's will really have a fit about the gas bill, but merrily pay the electric....screwed up, yes, but it's reality.


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