2 days after the installation of a AC/Heat Pump unit onto my existing fuel oil/forced air furnace (during the AC season), the 20amp screw-in fuse on the side of the furnace blew. The installer returned with a slow blow 20 amp fuse and this worked fine for the remainder of the hot weather AC season approx. 2 1/2 months. After manually switching over to the heat pump w/cooler weather the slow blow fuse failed after about 2 weeks. I asked the fuel oil furnace service man to check the elec. Draw on the furnace blower motor, etc. He stated that they were within normal ranges but that there was a slightly larger than normal draw when the burner was on and then the blower started. He told me to keep an eye on it and 2 week later the fuse blew again. This fuse never blew on this furnace for nearly 15 years and the installer is suggesting that the fuel oil furnace blower motor is perhaps the culprit and I should get a new one. What are the proper steps/tests to perform to determine the cause? I am feeling like I cannot leave my home unattended during the winter for fear that the fuse will blow at any time now.

If there is slightly larger than normal draw when the burner was on and then the blower started, someone needs to find out why,, on the side of the blower motor it should tell you what the LRA the amps what the motor should pull on start up ( which is normally at its highest on start up) .also on the tag with other info about furnace it should tell you how many amps total that the furnace needs to opporate

Don`t think the installation of the new heatpump has anything to do with your problem as the h/p should have its own dedicated breaker