There are 3 levels of electric heat chosen by which cord is used and based on available power. Ask the installer if he is using the 5kw element? Shouldn't be a fuse or breaker issue if the fan blows. How cold is it outside? If above freezing, the compressor should be running backed up by the electric strips. Sounds like the dealer needs to check it out. As for barely keeping up, that's a sizing issue if the thing is wired properly.
I did have the unit removed and replaced due to a clogged drain pan, and I haven't tried to run the unit's heat since, so I am wondering if maybe something like the element was damaged.
It is not cold outside (high 50s) and the unit is blowing cold air. I know that it is a sizing issue mainly, but I was just wondering if there were actually 3 levels of heat output. You are saying that this is limited by the available power though. I wonder if it is working to it's maximum abilities? What is the 5km element exactly? Are there supposed to be electric strips, like on a forced radiant heater? Do they usually come with the unit, or is this something that is put in additionally. Thanks for the help.