When you sell property, the gain equals the sales price less the adjusted basis.
By wanting to take additional depreciation, you are now just reducing your basis which will in turn increase your gain. This essentially may be a wash depending on your tax bracket.
The reason for this, is because when you sell the property you will have depreciation recapture to the extent of depreciation taken (allowed or allowable). Since this is real property, the rate will be capped at 25%.
Additionally, I would make sure that you have some realistic position of how you are allocating the sales price.
If you think this through, you have an overall gain on real property. If you attempt to reflect "no gain" on the HVAC portion, this just increases the gain in another area of the real property; once again effectively not accomplishing anything.
*A reminder that posts in a forum such as this do not constitute tax advice.
Also keep in mind the date of replies, as tax law changes.
