Blog Post

Froling P4: A High-End, High-Performance Pellet Boiler

P4 Pellet Boiler
Froling pellet boilers from Austria represent state-of-the-art in biomass combustion. Photo: Froling. Click on image to enlarge.

Froling is a leading Austrian manufacturer of wood-burning heating equipment. The company's cordwood and pellet boilers distributed in North America by Tarm Biomass (previously BioHeat USA), in Lyme, New Hampshire.

The P4 is Froling's line of advanced pellet boilers. These boilers are available in four sizes and eight different heating capacities (see chart), ranging from 35,800 to 200,000 Btu/hour. All are clean-burning and operate at efficiencies between 85% and 87%.

Tarm Biomass has been selling the P4 in the U.S. since 2009, while it has been available in Europe about five years. Most Tarm Biomass sales continue to be for cordwood-burning equipment (from Tarm, Scandtec, and Froling), but "the pellet boiler is starting to get some traction," according to Chris Hoskin, the dealer coordinator at Tarm Biomass. One of the challenges in selling pellet boilers is that they are designed to handle bulk pellets, and the infrastructure for bulk pellet deliver is just getting off the ground. (Most pellets are sold in 40-pound plastic bags.) "It's been a chicken-and-egg situation," Hoskin told me. Until bulk pellets are available, there is reluctance to put in pellet boilers that require them, but until more of those boilers are in place, it's hard for pellet suppliers to invest in bulk pellet delivery equipment. Fortunately, according to Hoskin, that's starting to turn around.

Cut-away drawing of a Froling P4 pellet boiler, showing the pellet hopper on the right. Illustration: Froling. Click on image to enlarge.

The P4 boilers have an integral hopper with auger-feed to the combustion chamber (see illustration). A vacuum pump at the top of the hopper periodically turns on to pull pellets from a bulk storage bin into the hopper. Such a bin is usually site-fabricated (see photo), with sloping plywood walls, and sized to require filling just once or twice per heating season.

An insulated buffer tank (usually 220 gallons or larger) is included in most systems to provide carryover and reduce the on-off cycling. When the boiler is operating it heats the water in this buffer tank, which is then used for hydronic space heating and water heating. The electronic igniter (a "hot-air gun") draws 1,200 watts, so reducing the on-off cycling can save significantly on electricity use.

The P4 boiler has sophisticated digital controls and fully automated operation with redundant safety features. The multi-pass heat exchangers have an automatic cleaning system that scours the inner surface and deposits ash in the ash bin, which can be easily removed for emptying. Because the boiler operates at high temperatures with controlled air flow, little ash is produced; the ash bin will only need emptying once or twice a month, according to Hoskin.


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A bulk pellet bin under construction in Dummerston, Vermont. Photo: Alex Wilson. Click on image to enlarge.

Froling pellet boilers and balance-of-system components are not cheap. A model 32 or 38 P4 boiler, which will be appropriate for most larger homes and small commercial buildings, costs between $15,000 and $20,000. Hoskin says that the entire installed cost for such a system will likely be around $30,000, including buffer tank, a site-built chip storage bin, and all other components. While pricey, Hoskin notes that this is less expensive than most ground-source heat pump systems.

Biomass combustion will play an important role as we try to shift away from fossil fuels in the years and decades ahead. Pellets provide a clean-burning option for doing that, and with advanced pellet boilers, such as the Froling P4, operation can be totally automated.

For more information:


Tarm Biomass

Lyme, New Hampshire


Alex Wilson is the executive editor of Environmental Building News and founder of BuildingGreen, Inc. In addition to contributing to this product-of-the week blog, he writes the weekly Energy Solutions blog. To keep up with his latest articles and musings, you can sign up for his Twitter feed.

See more on this product in the GreenSpec Guide

Published February 25, 2011

(2011, February 25). Froling P4: A High-End, High-Performance Pellet Boiler. Retrieved from

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