Ohio Rev. Code § 735.05
The director of public service may make any contract, purchase supplies or material, or provide labor for any work under the supervision of the department of public service involving not more than the amount specified in section 9.17 of the Revised Code. When an expenditure within the department, other than the compensation of persons employed in the department, exceeds the amount specified in section 9.17 of the Revised Code, the expenditure shall first be authorized and directed by ordinance of the city legislative authority. When so authorized and directed, except where the contract is for equipment, services, materials, or supplies to be purchased under division (D) of section 713.23 or section 125.04 or 5513.01 of the Revised Code or available from a qualified nonprofit agency pursuant to sections 4115.31 to 4115.35 of the Revised Code, the director shall make a written contract with the lowest and best bidder after advertisement for not less than two nor more than four consecutive weeks in a newspaper of general circulation within the city or as provided in section 7.16 of the Revised Code. No expenditure subject to this section shall be divided into component parts, separate projects, or separate items of work in order to avoid the requirements of this section.
R.C. § 735.05