Custom products loop breaks woocommerce template

I’m trying to list all products of a category in the content-product_cat.php template.

But if i use the official snippet for custom loops, the woocommerce loop breaks
global $woocommerce_loop;

Without using the snippet, the $woocommerce_loop contains this informations:

First iteration:
Array ( [loop] => 1 [columns] => 3 )

Second iteration:
Array ( [loop] => 2 [columns] => 3 )

When using the snippet, the $woocommerce_loop gets empty:

Array ( [loop] => [columns] => 3 [column] => )

http://wordpress.org/extend/plugins/woocommerce/