Longwood Dual Fuel Furnace Manual Download. — Heating Help foruminghelp›THE MAIN WALLLongwood Dual Fuel Furnace Manual Download. trenten Posts: 1 Member. December 2014 in THE MAIN WALL. Just bought a home with a Longwood VII duel fuel furnace with auto damper control. Wood burning auto damper has been disconnected as the owners weren't using it. Need a manual to try to get it back to normal operation. Longwood Duel Fuel Furnace Mark VII Manual | Arboristsite wwwristsite›Forums›Tree Care ForumsJun 05, 2009Longwood Duel Fuel Furnace Mark VII Manual. Discussion in 'Firewood, Heating and Wood Burning Equipment' started by iowa, Jun 1, 2009. They also are called longwood because you needed long wood to fill the box to get the burn times you'll need to heat a 3000 s/f house.