You also need a license & to know exactlywhat your doing.
If you don't, go directly to jail.
What happens if you get a leak?
What happens if someone comes after you & they don't know whats in it.
Its highlt flammable.
You have to take it very seriously, as back yard operators trying to save money are going to hurt people.
A domestic fridge is not worth woorying about due to very small charge.

DON'T DO IT UNTIL YOR FULLY TRAINED AND LICENCED

We all know it works so don't experiment!

Who are you saving money, you or client?