What is the asset class for Grain bins that are rented out for income. Can I use the section 179 deduction How many years do I have to depreciate this property?

I purchased an acreage that included 4 grain bins that cost $34,733.00.  I rent the bins out and have received income for 2016.  Using your software.  I selected the Section 179 depreciation expense and it actually reduced my refund.  When I selected the three year %200 Declining Deprecation it greatly increased my refund.  I don't understand I thought with Section 179 I should have been able to write off the entire expense in the year purchased 2016