Multiple WordPress on Virtual Host

Question

I have AWS EC2 Linux server. Currently only one wordpress multisite mode is hosted in root folder (/var/www/html).

Now I would like to host another wordpress site. So that I have enable apache virtual host.

Here is my vhost.conf

NameVirtualHost *
<VirtualHost *>
ServerName firstdomain.com
ServerAlias www.firstdomain.com
DocumentRoot /var/www/html
</VirtualHost>
<VirtualHost *>
ServerName seconddomain.com
ServerAlias www.seconddomain.com
DocumentRoot /var/www/html/seconddomain.com
</VirtualHost>

I have one php test file inside seconddomain.com folder and I can browse by www.seconddomain.com

After that I download wordpress and copy into seconddomain.com folder and change the wp-config.php.

But I got the error "This webpage has a redirect loop".

Is it because I have one wordpress in root folder or other security reason?

Regards, Alex