Permit fees are based on the total cost of the construction. If a project only includes a single trade, you may pay a fee for a trade permit. If two or more trades are involved, an all-inclusive building permit may be requested.
Please note that if the mechanical permit is part of an all-inclusive building permit, then the fees are paid at the time that the building permit is issued.
See the document “Building Permit & Plan Review Fees”.Building Permit & Plan Review Fees