Start depreciation from the time it was installed.
Please see this answer from Hal_Al:
It's an improvement and is depreciated over 27.5 years.
However, there is a relatively new tax break that will allow you to elect to deduct it all this year.
You can still use the De Minimis Safe Harbor election for improvements Up to $2500.
Reference: https://www.irs.gov/businesses/small-businesses-self-employed/tangible-property-final-regulations
