CentOS 7 Linux was distributed until now only for 64-bit as reported 2 months ago, but the RHEL-based operating system is now available for 32-bit (i686) platforms.
According Johnny Hughes from CentOS “The Beta release of the 32-bit (i686) Architecture of CentOS-7 (1503) is currently on build logs.” As stated on the CentOS mailing-list.
The 32-bit edition of CentOS 7.1-1503 is still in Beta, but you can expect the final version soon.
CentOS 7.1-1503 Beta has been made available for download only as a boot.iso image that allows you to boot it and then start adding packages from the Internet to get a complete installation.
You can download the boot.iso here.