micro zones & condensing boilers

Phil_8

Are micro zones a problem for condensing boilers? Should a buffer tank be considered or is it not needed with condensing boiler? I would guess that even the best condensing boiler's life would be extended if short firing times were minimized.

Mike T., Swampeast MO

I would guess that even the best condensing boiler's life would be extended if short firing times were minimized.

I'd tend to agree. One of the many great things about TRVs/FHVs is that you can "micro-zone" to the nth degree but the boiler won't start cycling until loss from the entire structure is less than low-end modulation. Yet another reason not to oversize--even with modulating boilers...

hr

How small is the

smallest zone, compared to the lowest modulating step? And how often could it be the only zone calling?

The very best place to store your heating energy is in the fuel sourse

Once you combust the fuel and turn it into hot water you need to pump it, store it, and keep it well insulated. All of these will take some "loss" to accomplish.

That, to me, is the biggest plus of modulating heat sources. Ideally they will get them to modulate down to a pilot light sized flame. Fire them up at install and never let them go out! Nice way to eliminateignitor and flame prove hassles

This would be a nice way to cover the range from near zero British thermal unit/ hour loads up to petal to the metal full output.

Still, there are times when a buffer is a good option. Critical is the piping of such! You need to be able to bring them online and off as the load dictates. Usually some version of P/S piping works.

Not a lot of sense turning a low mass 1 quart boiler into a 50 gallon volume, boiler. May as well buy a condensing tank type heat source if that's the case. Skip the modulating feature and just pull off the tamnks capacity as needed.

Siggys HDS has a great module for playing "what if" buffer options. You can play with delta t, tank size, load size, insulation factor, etc. It will answer you "should I" question with some solid numbers.

You should be able to test drive a demo at www.hydronicpros.com

hot rod

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Phil_8

micro-zones & condensing boilers

Thanks Mike & Hot Rod,

I have Sigy's software and his book. Will try to determine the burn time for smallest zone at the lowest modulation level. You Missouri guys are always a great help!

PD