When I enter my Mortgage Interest Credit Certificate (MCC), my federal refund increases by $2,000 despite the fact that I have no federal tax liability.

I have no federal tax liability, I am due a refund. I understand the MCC is a non-refundable tax credit so why it is increasing my refund by $2,000? I don't want to file and receive more money than what I am due and then end up owing money back to the IRS. Is this a TurboTax issue or am I missing something? I'm working with TurboTax Deluxe online version.