I am not an accountant, but the following excerpt explains it fairly well.
The Boiler is part of the heating system. Therefore, if the replacement of the boiler did not " better or adapt" the HVAC system overall it is an expense. However, since you changed out the boiler and the components to make it individual systems, that will be an adaptation or betterment, and your accountant may confirm it was a Capital improvement.
Unfortunately, the Bonus depreciation extensions ended at the end of 2013.
You might investigate whether there is some way that your new system qualifies for a MACRS accelerated depreciation. Certain alternate energy components, they qualify for a shortened depreciation period.
In any case, by shifting the heating costs, you've increased the value of your asset pretty dramatically.
From bizfilings.com/toolkit/sbg/tax-info/fed-taxes/cost-of-capital-assets-not-deductible-expense.aspx
Beware: Buildings Are Actually Multiple Units of Property
If you own a building, you already are aware that there are numerous systems within that building, such as the plumbing system and the heating system. For purposes of determining whether an expense or a repair, each of those systems is considered a unit of property. So, you have the building structure as one unit of property that contains the following distinct units of property:
- Heating, ventilation, and air conditioning (HVAC) systems. This includes all motors, compressors, boilers, furnace, chillers, pipes, ducts, radiators.
- Plumbing systems. This means all pipes, drains, valves, sinks, bathtubs, toilets, water and sanitary sewer collection equipment. It also includes any site utility equipment that is used to distribute water and waste to and from the property line and between buildings and other permanent structures.
- Electrical systems. Included are wiring, outlets, junction boxes, lighting fixtures and associated connectors. As with plumbing, this also includes any site utility equipment used to distribute electricity from property line to and between buildings and other permanent structures.
- Gas distribution systems. As with other utility systems, this includes the pipes and equipment used to distribute gas to and from property line and between buildings or permanent structures
- Elevators. All elevators in the same building are treated as a single building system or unit of property. In effect, each separate elevator is a component (part) of the elevator building system.
- Escalators. Just like elevators, all the escalators in a building are considered a unit of property.
- Fire protection and alarm systems. This includes sensing devices, computer controls, sprinkler heads, sprinkler mains, associated piping or plumbing, pumps, visual and audible alarms, alarm control panels, heat and smoke detection devices, fire escapes, fire doors, emergency exit lighting and signage, and fire fighting equipment, such as extinguishers, hoses); and
- Security systems. Among the components included are window and door locks, security cameras, recorders, monitors, motion detectors, security lighting, alarm systems, entry and access systems, related junction boxes, associated wiring and conduit).
You need to test whether the costs you incurred bettered, restored or adapted the particular system, not the impact on the building as a whole.
When you purchase a building, the building structure and all of the various building systems are depreciated as a unified whole based upon the cost of a building. However, this scheme is radically altered when a building system is replaced or when improvements are made to it. In that case, the cost of the improvement is separately depreciated using the modified cost recovery system (MACRS) periods that applies to the building