Arrived at the job for a new Fujitsu installation. Turned off the power and disconnected all wiring to the unit. Next we removed all the gas lines, return duct, exhaust and other miscellaneous items. We brought the new furnace up to the attic and fitted it in place. We connected the ac coil cabinet and return duct. We re-routed and connected all electrical wiring including the low voltage. We reassembled all the gas lines, purged and checked for leaks. Installed the exhaust lines and taped the joints. We fired up the furnace and allowed it to run and cycle for a few minutes, Job completed.