Is there High efficency steam

mark ransley

There are 90+% efficent boilers that heat water, and large commercial 90+% steam boilers. Are there small home sized high efficency 90+% steam boilers. I can only find 82-83% efficent small steam units. If not why are they not made, can a retrofit capture wasted heat.

Brad White_200

High Efficiency Steam

Your best combustion efficiency would be in the 3-pass oil-fired steamers, with any gas offerings (limited in that type) coming in a few percentage points less.

Below that, as you say, 82-83% seems to be a common spot.

As you know, steam works above the condensing temperature of flue gasses, so condensing is out for most residential applications. Only vacuum steam can operate at lower temperatures, but even so is still above condensing temperatures in that practical application.

On commercial and industrial boilers, there are flue gas heat reclaim devices to pre-heat the boiler feed water. That of course belies that these are process boilers and use most of their feed water as a total loss toward the process; very little of the condensate is returned compared to a residential steam heating system.

As you know, to reclaim heating energy, you need a place to put it and that place has to be a medium cooler than the source of course. Pre-heating domestic water comes to mind, but is that always available? Mostly yes at least in storage form.

There have been flue gas reclaim devices out about 25-30 years ago which were down-right dangerous. Flue insert exchangers with tubes and fans to heat the basement. I had one on a house I bought. You could hear the hissing of the condensate on the CI sections. Never did test for CO or out-draft/spill. I ripped it out.