As I’ve reported in earlier blogs, my large, old farm-style house in Bethel, Maine, was heated experimentally last winter with a four-section pellet boiler. The Janfire-fired system is rated at 23 kilowatts, about 51,000BTU/hour. The system heated the house to our satisfaction pretty well last winter with the exception of a few “design days” when outside temperatures dropped below zero. On those days, we were faced with a house at, or below, 60 degrees F, or burning a bit of oil to support the pellet boiler.
During this past Christmas seasons, my 86 year old mother joined us for two weeks. Our standards for suitable heating (67F, or so) didn’t work for her, so we needed to try to keep the house at 70F at a minimum. The little boiler fired at capacity much of the season to meet the demand and was generally successful. However, on days when single digit to sub-zero temperatures struck, there was no way. The boiler is just too small to fill that demand largely due to heating time lost to the ashscraping cycle of the top-fed burner. To meet the need, I set the oil boiler to fire when water temperatures dropped to 160F. All worked well; the boiler fired occasionally, generally following an ashscrape cycle when water temps would drop below the target level. My mother was warm and little supplemental oil was burned. During the past heating season, I used a total of 40 gallons of supplemental oil.
It is my assumption that a small boiler of the same capacity of an underfed pellet burner design that did not require lost time to ashscraping would meet my demand without support from the oil boiler. It would be fun to test the assumption.
Because I’ve been able to use an extended ashscrape cycle due to the improvements in pellet quality, I haven’t been cleaning my boiler as often as I did last year. That’s been a mistake. In this particular Bosch/Janfire system there is ample opportunity in the cast iron boiler for ash to reduce boiler efficiency. I’ve returned to a two week cleaning cycle for this boiler to keep efficiency up and pellet consumption down.
In the interest of full disclosure, Dutch Dresser is the Managing Director of Maine Energy Systems which sells both the Bosch/Janfire system referenced here and the more advanced AutoPellet systems made under license from OkoFEN of Niederkappel, Austria.