Fair Market Value (FMV)

Read http://www.irs.gov/publications/p946/ch04.html

First, find out the FMV of the old appilance when you start use it in the rental property. 

"If a new appliance is purchased for one’s home and the old one is placed in the rental then the amount used for depreciation is the value of the used one at the time it was placed in the rental property"

http://www.easyrentaltools.com/index.cfm?event=article&title=appliance-depreciation

Second, find out the "General Depreciation System" table for your appliance. It might be under 2-year, 3-year ... depreciation.

http://www.irs.gov/publications/p946/ch04.html#en_US_2013_publink1000107513

Third, look up depreciation table for per year depreciation, it is not proportional

http://www.irs.gov/publications/p946/ar02.html#en_US_2013_publink1000107772