Suburban 35,000 BTU Furnace (SF-35FQ) (2400A)Suburban 35,000 BTU Furnace (SF 35FQ) (2400A) At only 7 1 2" tall, these quiet yet efficient, low profile ducted furnaces feature multi ported stainless steel burners, sealed forced draft combustion, automatic direct spark ignition and low amp draws. With up to nine duct connection choices, these models offer almost unlimited design flexibility. The Sf Fq models do not require exterior access doors which make them the more economical installation