GE oil furnace,
They made both warm air and boilers, both steam and hot water, the warm air was really something!! the blower was at the top of the return air side, it blew down thru the hear exchanger passages then up and out the other side, same downward firing burner!The whole mechanism was controlled by a timer similar to a dishwasher timer, it started and advanced thru the run ctcle then when the thermostat was satisfied it shut off and reset itself for the next cycle!