I don't know for certain, but I always assumed this was done just so it could hold the crown for "highest efficiency available". They just used a really big heat exchanger for a really small furnace, and bam, it sets an efficiency record.
This is pretty common practice in this industry. They do the same thing with air conditioners and heat pumps- just pick one particular size and configure it to get better efficiency than the other sizes in the same model series. Than quote *that* number in all the advertising.
Originally posted by thurston Carrier 58MVP040 Why is this unit wider than the rest of the line?
Is it old stock?
I had one of these installed in March 2004, it was of recent/current manufacture. if I had to take a guess (which is the best I can do here anyway), I'd say that wyounger's post is probably right on the money.