Took me longer than it should have to understand the way Prestashop handles free shipping when the order is above a certain amount. The biggest problem is that I was looking in the wrong place. So that you don waste as much time as I did here’s how to configure the Prestashop 1.6 options to offer free shipping with purchases above a set price.
First log in to your Prestahop 1.6 back office (of course)
Click on Shipping in the left panel and then click Preferences
Here you can set a handling fee. I personally recommend using small handling fee (under 2$) most people will be happy to pay such a fee if your price is right and it helps cover costs and therefore you can keep your advertise price as attractive as possible.
You can also set the minimum price to which free shipping will be applied. If you want to offer free shipping for orders over (say) 25€, set it here in the box called “Free shipping starts at 20”
That should be all you need to to to have free shipping in Prestahop 1.6 for orders above x amount.
NOTE: Once you have frees shipping for doers above a certain price, shipping costs will simply dissapear in the front end. Prestashop 1.6 does this calculation realtime. So as the price of the good you have in the basket changes, the shipping costs will appear/disappear based on the setting you put in the shipping>preferences. You can try it out by going to you shops front en and adding a single product. In the cart view increase the quantity of products until it passes the shipping minimum using the +- buttons. If everything is configured correctly, the shipping cost will disappear when the price exceeds the minimum for free shipping you have set.
Now you should to go to the Sipping option again in the left pane and then choose Carriers. You should take the time to configure the courier companies and shipping option you will offer in your Prestahop 1.6 online shop. NOTE: You can set it so that all orders by a certain courier are free regardless of the price of the order. Set this under the options for the Carrier (by clicking edit for that carrier) and click the tab: Shipping locations and costs>turn “Free Shipping” to 'yes':