Is your company doing it wrong like everybody else??? low mass pitfall

Discussion in 'HVAC Heating & Cooling' started by NedFlanders, Sep 21, 2011.


Do you use a buffer tank with baseboard heat

  1. Yes

  2. No

    0 vote(s)
  1. NedFlanders

    NedFlanders New Member

    Sep 20, 2011
    Master Plumber
    I am new to this forum, only came here to see if anybody had mentioned turbomax water heaters. Wanted to see what others have found.

    I found the post with not a lot of actual hands on experience, just folks running the numbers to compare with a boilermate or superstor.
    Everybody was talking only about gal per min of hot water.

    This is only half the reason to use a turbomax.

    I have found that most if not all condensing boilers hooked up in a typical home do not condense very much at all. There is a very good reason why this is happening. It is because they have not followed the directions in the manual and have not followed proper engineering practices. I will admit that the directions try to hide the truth about how you HAVE to hook them up to work properly. A lot of the time they will just tell you to adhere to some approved standard so they dont have to break the bad news about how you have to add a buffer tank in order for it to work right.

    Thats right you need a buffer tank. You might be able to get away with not having one if your heating system is just right and can deliver enough cold water back to the boiler. This is normally not the case. Most people have baseboard heat. Baseboard heat does not work with a low mass boiler without a buffer tank. Well it works (most of the time) but it is not efficient , and defeats the whole purpose of getting a condensing boiler. And in some cases will not work at all because the boiler will overheat.

    You need to size your boiler to keep with the hot water demand of your customer. This size boiler normally can not turn down low enough to support small zones of baseboard heat. This is believed to be the leading cause of problems with this style boiler, It causes short cycling and overheating .

    Baseboard heat is supposed to be hot all the way to the end of your loop. Which means the water going back to the boiler is hot...too hot for the boiler to be efficient and condense.

    A buffer tank is always cooler on the bottom and that is what you send into the boiler, you only heat the top of the tank that is sent out to the heating system.

    I like the turbomax because it kills two birds with one stone. You get a very impressive water heater and a buffer tank in one. To put a boilermate as a zone is a real rip-off to the customer and is the wrong solution and if the customer was smart enough could sue you for not following the code.

    Thats right I am going to argue that is is a code violation to not put a buffer tank with this style boiler hooked up to baseboard heat.

    It does not jibe with ASHRE standards or any math that I can come up with.

    I asked every rep from every boiler company about this and they ALL quietly admit im right and more than one sais the turbomax is the best way to go.

    Burnham boiler company will not honer the warranty on their boilers without a buffer tank. See if you can find this in writing anywhere......Their lawyer says we referred you to use ASHRE and ANSI standards as the ultimate way this product needs to be hooked up.

    They are not the only ones who will do this, nobody comes out and admits it at first. Instead they try to make you believe that a low loss header is supposed to prevent this. And most of you buy it. That has absolutely NOTHING to do with fixing that problem, that is NOT what a low loss header is for and never has been. And anybody who believes it is not thinking and has no business installing heating systems. Low loss header was made because most guys couldn't figure out how to wire a primary secondary loop set up let alone pipe it right.

    My "low loss header" is my buffer tank. It is actually supposed to be called a hydrolic break or separator anyway but that didnt sound "easy" enough.

    I also have helped a slightly undersized oil boiler keep up and stop condensing, now it is easy to clean and works better. The customers are always amazed by the difference when I switch them over.

    Most boilermate I see have been piped with 3/4 pipe not inch and have 007 circ on them this isnt boilermates fault but it a common reason why they dont work very good. Also in towns with a lot of dirt in the water they clog the heat exchanger and the design of the water flow in the tank does not fix it. The turbomax self cleans.

    Bottom line the turbomax is a very good product IMHO much much better that a boilermate.
    I also love the added side benefits it offers the boiler.

    oops bored now gotta run


    PS Not a rep for anybody just like the product
  2. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona
    If the TurboMax is NOT on a zone, that must mean the boiler is running 24/7 in order to keep the hot water supply side satisfied, OR do they only get hot water when the system calls for heat?
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  4. Dana

    Dana In the trades

    Jan 14, 2009
    It depends on how you control & plumb it, but usually it works just fine to set it up as the boiler's ONLY zone with the aquastat on the TurboMax at the min design-day temp requirements and call it a day, and run the heating zones with a separate circulator/valve system sipping off the tank. That makes the TurboMax basically a fat high-mass hydraulic separator in a funky primary/secondary, in much the same way that a BoilerBuddy does. If plumbed as a separate zone the thermal mass isn't involved with space-heating burns. Since it's hard to get predicable output on fin-tube with temps below DHW temps, it mostly works.

    The amount of condensing you get out of it is a bit in question though. The stratification delta-T in the tank isn't any where near 20F between the boiler intake an the heating-system water output port when the heating system is running- more like 10F (I've measured it in a 48gallon system with a ~2gpm boiler loop flow and ~1gpm heating system flow), but it can exceed that in water-heating mode. If you need to set the aquastat at 140F to cover design conditions the best you'll do in space-heating mode is ~87-88% (not bad, really). If you can set the tank to 125F or lower, you'll break 90%.

    Setting the outdoor reset curve of the mod-con can be a bit tricky too- you don't want to exceed the max delta-T and stress the boiler, but you want it to be high enough to deliver reasonable DHW capacity at as-low-as-possible tank storage temps.

    The other way to do it is to plumb it in series between the radiation returns and the boiler ignoring the aquastat, using it DHW pre-heat. Most of the heating season it'll be supplying the lion's share of the DHW, and it'll deliver more condensing since the boiler outdoor resent can be set lower since the heating water is then undiluted by the tank, but that approach requires another HW heater. Knowing the radiation's actual average and design day temp may determine which approach makes more sense.

    ErgoMax and the Everhot EA series HW heaters can be utilized in the same way.

    In my own home I run an ErgoMax set to 130F, and run a fixed output temp on the boiler setting the flow & delta-T to ~1.3x the homes design day heat load. As the tank temp drops under DHW load, the lower return temp at the boiler input makes it modulate up, and by the time the bottom of tank drops to 110F it's putting out plenty- enough to run the shower all day long (in part due to a drainwater heat exchanger on the potable cold feed). But I'd have to crank up both the storage temp and boiler temp to fill a soaking-tub with all zones calling for heat. With the air-handler zone running the bottom of the tank stays around 117-120F, but with the staple-up radiant floor zones it's only at condensing temps on a cold startup. If the radiant kept up at 125F on design day I could get it to pretty much stay in the condensing zone all the time. (I'll probably swap out the cheapie sheet metal heat spreaders for some extrusions one of these years, but there's no payback in it at current gas prices.)

    [edited to add image]

    Last edited: Sep 22, 2011
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