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coil vs indirect

Constantin
Constantin Member Posts: 3,796
in THE MAIN WALL
... because a hot-water boiler with a coil has to keep the water inside it super-hot all the time to achieve the ΔT and flow required to keep you and your wife from running out of domestic hot water (DHW). With a indirect, you can de-couple the boiler water temperature from the DHW needs, allowing it to run at lower temperatures most, if not all the time.

Lower boiler temperatures in turn will reduce it's standby losses. Flue stack losses are also likely to decrease (unless you have a damper) as the hotter air in the flue on standby will draw more BTU's up the chimney than on a cooler boiler. Since an indirect does not have any flues running through it, it can be much better insulated than a boiler.

I'd investigate the possibility of retrofitting a outdoor reset controller and the indirect as a way to reduce your fuel needs. If your boiler mfgr allows your boiler to be fired across a broad range of input ratings, I'd also investigate the heat loss of your home and adjust the firing rate accordingly.

Comments

  • Jim_109
    Jim_109 Member Posts: 45
    coil vs indirect

    what if anything would I be gaining if I switched from a coil hot water system to an indirect?

    With only two adults, we have never run out of hot water. We do not run fixtures/applicances at the same time that demand hot water.

    Though from what I read indirects are more efficient, in my case would they by less efficient by keeping all that water hot throughout the day? Not to mention the addtional cost for parts and labor. I may never acheive a payback
  • Al Letellier_9
    Al Letellier_9 Member Posts: 929
    tankless vs. indirect

    I agree wholeheartly witn Constantine on this one. I went from a coil to an indirect with a Tekmar reset controller and fuel consumption for this house with 2 adults went from 815 gal/annually to 400....worth the investment.
  • J.C.A._3
    J.C.A._3 Member Posts: 2,980
    I agree....

    Also. The payback will be short, and the COMFORT will be long.

    The indirects now available have standby losses in the 1/4° per hour range.Unlike your coil connected through the flue of the boiler, the boiler will fire less to "maintain" a setpoint temperature.The water stored will keep warm enough, and be sufficient enough to lighten the load on the burner,after all, the most effecient boiler is the one that ISN'T running!

    Al made the best point. With controls available now, you can also have the best of both worlds. A Tekmar 260 is the choice in this case.(a Taco 700 would also be a consideration) You will be able to reset the boiler by the outdoor temps, and have it fire to the high limit during a call for hot water. Win/Win...in my book.

    The cost will be considrable, but the payback will come quickly...especially if the price of fuel goes higher. (anyone see it going the other way?) Chris
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