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Low loss header versus buffer tank.

icy78 Member Posts: 404
So I've seen a number of mentions lately on this site concerning low loss headers. Looking for thoughts on when, to use a low-loss header?
When is a buffer tank preferred over a low loss header ?
That type of conversation.


  • GroundUp
    GroundUp Member Posts: 1,924
    LLH are for hydraulic separation, buffers are to prevent short cycling of the boiler. They serve totally different functions
  • icy78
    icy78 Member Posts: 404
    > @GroundUp said:
    > LLH are for hydraulic separation, buffers are to prevent short cycling of the boiler. They serve totally different functions

    Well that's what I was thinking. However in the last few weeks I have seen comments that make the two sound interchangeable. It could be that it was in reference to such a small amount of buffering needed that a generously-sized low-loss header could take care of the small difference between boiler turn down and lowest BTU load?
  • hot_rod
    hot_rod Member Posts: 22,254
    The best route would be ti identify the smallest zone, in BTU/ hr.

    Then look at the boilers lowest turndown, how do the match up?

    A sep and related piping would add a few- maybe 5 gallons of capacity. Plus dirt, air, hydraulic and magnetic separation.

    The buffer, properly piped could supply the similar function air, dirt and hydraulic but also add however many gallons the tank is.

    I know of no hard and fast rule for determining when a buffer is worth the added cost, it comes down to then load match and how much on/ off cycling you can tolerate on low load, mild day conditions.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • clammy
    clammy Member Posts: 3,113
    I have a caleffi separator on my system w a mod con . It serves its purpose and saves space in lieu of p/s piping as to distance before and after your tee s ,so in a limited space it s a no brainer to me and they do give pretty good temperature diff as to not much bleeding and still good td across boiler. As for buffers and using a 2 or 4 port I prefer a 4 port and a buffer that is tall and narrow seems to get better td across top and bottom of the tank more separation . I would say if using a system sensor to put it on the outlet side instead of the tank unless the well is hi other wise you will lose the thermocline temperature diff in the tank . As hot rod stated I used a buffer for the issue of small micro zones that where below the mim modulation of the boiler and I was satisfied w the way it worked . You really have to do the math or just run as one zone and balance the emitters and possibly use trv ,it’s one of the reasons I like panel rads w by pass valves on constant circ w a boiler buddy and a mod con . You can go either way low temp $ large panel rads or mid 150 hi on design and save a little bit on the panels . I usually just add a ETD to run the pump based on outside temp and have the boiler made by the stat . It of course takes up more space and adds to cost but in the systems I ve incorporated into there’s no short cycling even when the smallest zones calls that not trv based emitter . It’s a great tool just have to think it’s merits and not go crazy Peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
  • Alan (California Radiant) Forbes
    Do you know how many buffer tanks I've seen here in the Bay Area? One, and I installed it. The owner asked for it because he learned about them here on HeatingHelp.

    We're kind of slow out here, but we'll catch up.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • icy78
    icy78 Member Posts: 404
    Thanks guys.👍