Buffer Tank

Mike T., Swampeast MO

Condensing or non-condensing really doesn't matter. What matters is modulating or non-modulating.

Even a properly sized modulating boiler (given the current limits on low-level modulation) could likely benefit from buffering when the load is below the modulation point.

Of course if you have a converted gravity system with TRVs and a Vitodens without low-loss header the heating mains <I>become</I> a buffer. I sincerely don't believe this is possible with any other current boiler unless you break the primary/secondary "rule" and develop your own variable-speed circulator control.

Adam_12

Here is a good topic for discussion.Could all noncondensing hydronic systems benifit from the use of a buffer tank ? { both high mass and low mass}.

Joe Brix

If you had a high mass boiler

and it could handle lower return water temps, I would think a buffer tank would be a waste of money.

hr

The best place to store energy

is in the fuel! Converting chemical energy to thermal, then insulating and storing it...?? You take some efficiency hit everytime you move it around, I think. Leave it in the oil tank, pipe line, or LP tank until it's time to convert it into heat.

Buffer tanks are, in my mind, a band air or maybe just an aid They treat a symptom, not the problem when designed around a grossly oversized heat source.

An exception or two may be using low, off peak, night time electric rates to charge a buffer for day time use. Suppose the electric utility would sell power for 2 cents a KW, off peak! That may pencil out, and make a buffer tank workable. Same with ME's idea of the ground source type storage.

These days small modulating heat sources can get down and dirty on low loads. Modulation down to 18,000 BTU/hr is pretty impressive. Currently that seems to be as low as they can get and keep a stable flame.

I hope to see them modulate down to a pilot sized flame and up 500 BTU/ hr to 10,000 would be a fun heat source to play around with.

hot rod

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Adam_12

I guess that nails it .Variable heat input is probably the holy grail of hydronics but for the modulating challenged ,buffer tanks still have a place.They can be used to purge heat stored in the boiler that would normaly go up the flue.In a nut shell there a hydronic capacitor,there just another tool in the toolbox.If a person wanted to size one,is there a formula that you use.You would have to know which load will cause the cycling ,the gpm and btu rating of the zone and finally the time you want the boiler to stay off. These things can get fairly large,another draw back.It s valuable to know the applications and how to design systems that incorporate them.

hr

To play buffer \"what if\"

Thge HDS has a module to size and toggle loads to see the changes. Easier than piping it in real life to see how it is going to perform

I'd still like to se a modulating, condending, tank type boiler. Something like a Voyager with a Munchkin burner. this would get you a buffer for small loads, modulation, high efficiency and a simple single footprint appliance. Put a 3" foam jacket around it, since you can with that type of unit...

hot rod

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siggy

I agree with Hot Rod

The best of both worlds. A reasonable buffering thermal mass (20 -30 gallons as a guess), contained in a superinsulated "thermos bottle" tank with an attached modulating burner. build in some good heat trap details and maybe a circulator and bypass for "no brainer" P/S installation. Modulation down to say 15,000 Btu/hr with buffering mass handling the smaller microloads without excessive burner cycling. Single footprint.

Siggy