The IRS does not specify a number of days for processing of a form 8862 provided to the IRS.  However, a general rule for processing is approximately 6 to 8 weeks if the IRS does not request additional information.  You may have to provide the IRS with additional documents or information before a refund relating to the EIC you claim is released to you, even if you attach a properly completed Form 8862 to your return.  This could further delay the processing of your return.

For further information, please refer to IRS Publication 596 - "Earned Income Credit (EIC)" at the following link: https://www.irs.gov/publications/p596#en_US_2016_publink1000298647