ver 2
Added Weight Limit (blank - no limit)
Fo example: free shipping over $100 but less than 20lb

ver 1
OpenCart functionality:
if you have a product for $55 and Free Shipping for orders over $50 - everything is ok
Added a coupon for 10% OFF - customer will receive Free Shipping anyway, because it's calculated based on subtotal.

This OCMod, will change Free Shipping module only:
It looks for everything in Totals except Taxes until Shipping.
So if the product for $55 + Tax - $5.50 coupon - there is no Free Shipping