Featured T4 Installation at the Marsh-Billings-Rockefeller National Historical Park

boiler house with door open showing boilers

Boilers: Fröling T4 150 (500,000 Btu/r) wood pellet/wood chip boiler.
Previously installed Garn WH1500 (177,000 Btu/hr) with a water capacity of 1,420 gallons.
Thermal Storage: The Garn’s water capacity is used as the thermal buffer tank.
Fuel Storage: 20’ shipping container modified for fuel storage
Fuel Delivery: Modified P4 cyclone (day hopper) suction device.
Sold and Installed By: Sunwood Biomass of Waitsfield, VT | 802.583.9300
Location: Marsh-Billings-Rockefeller National Historical Park | 54 Elm Street | Woodstock, VT 05091 |

There is a mandate to invent an entirely new kind of park. It must be one where the human stories and the natural history are intertwined; where the relatively small acreage serves as an educational resource for the entire National Park Service and a seedbed for American environmental thought; and where the legacy of American conservation and its future enter into dialogue, generating a new environmental paradigm for our day. (John Elder, author and Middlebury College Professor Emeritus, From a speech at the opening of the Marsh-Billings-Rockefeller National Historical Park, June 5, 1998).


Tarm Biomass has had the privilege of providing two boilers for Marsh-Billings-Rockefeller National Historical Park, in Woodstock, VT. We applaud the National Park Service for its efforts to prove the value of an environmentally sustainable National Park System. This post is about the most recent installation of a Fröling T4 150 automatically fed and fired wood pellet boiler for heating a 30,000 square foot mansion at the park.

There are two boilers housed in the Mansion’s garage, which are used to heat approximately 30,000 sq. ft. The Garn wood boiler was installed a few years ago and reduced the Mansion’s oil consumption by about 50%. With the new Fröling T4 150 boiler installed, there is no fossil fuel consumed at the Mansion. Previously, the Mansion consumed 33% of the oil used at the park.

There were two unique challenges with the installation of the new T4 150. Both challenges were caused by a lack of space for bulk wood pellet storage and for a thermal buffer tank in the garage. Yet, the Park Service could not allow for the construction of additional buildings.

With the help of National Park Asset Management, LN Consulting, and the installing contractor, Sunwood Biomass, a plan was developed. A portable 20’ cargo container was chosen for the wood pellet fuel storage. The storage container ingeniously includes sloped floors, a Fröling suction screw auger system, fuel level sensors, fill connections, and all necessary safety devices. Because the Park Service also did not want the wood pellet fuel container visible during the busy summer season, the wood pellet fuel container is removed between early spring and late fall. To remove the wood pellet container easily, quick disconnects for both fuel and electrical were installed. Normally the Fröling T4 150 is not equipped for pneumatic delivery of wood pellets, but a hybrid fuel delivery system was created using portions of the fuel delivery system from a Fröling P4 pellet boiler. Pneumatic fuel conveyance through small, flexible hoses makes disconnecting the fuel lines a snap. The fuel storage container was even painted forest green and adorned with Park Service emblems.

During the summer, the Garn wood boiler is used for domestic hot water and any small heating needs.

The second challenge, including an adequate thermal buffer tank to improve boiler performance, was met by utilizing the built-in water storage of the Garn wood boiler. The Fröling T4 operates best with approximately 1000 gallons of buffer, so the 1,500 gallons in the existing system was a perfect solution.

There is one other Fröling boiler installed in the park. In 2013, a Fröling P4 32/38 wood pellet boiler was installed in the Double Cottage building, which includes two staff housing units. The P4 replaced an aging oil boiler and furnace. The building is now entirely free of fossil fuel.


The Marsh-Billings-Rockefeller Mansion


Alternate view of boiler house and pellet container

A view of the Mansion’s garage that houses the boilers and the pellet fuel container

Pellet container being moved

Pellet container being off-loaded

Combination of container images

Three views of the pellet container showing fill and building connections

Photo of inside of pellet container

Inside view of the pellet container

Full view of boiler house with door open showing boilers

Front View of garage housing the boilers

Front view of boiler and feed system, Garn in background

A closer view of the Fröling T4 Boiler

Close up of cyclone on feed auger

A close-up view of the pellet suction and day hopper



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