A Siegler furnace is a heater specifically made for a mobile home. Lear Siegler is a defunct company that produced the Siegler furnace and other HVAC equipment. In 1986, LSI Home Division was sold to Nortek, which began selling the same products under the Miller Heating and Air Conditioning moniker.
The Siegler furnace came in a variety of different makes and models that varied in gas and propane operation. Since taking over the brand, Miller Heating and Air Conditioning has expanded the brand to 16 different models of seasonal energy efficiency ratio air conditioners and heat pumps offered in a variety of combinations. Heaters are available in gas, electric or oil-burning variations, as of 2015.