When I create a combined property in CES Selector, and change the unit system, the conversion is wrong.
The most likely cause of this is that you are using some type of constant in your combined property—for example—8.314 * [Melting Temperature]. When you change unit system, the value of [Melting Temperature] is changed to reflect the new unit in which it is measured in the new unit system, but the constant has no units and its value is not altered. To assign a unit to a constant, you should open the database in CES Constructor, go to the Database menu at the top of the screen, select Database Properties and select the Constants tab. Here you can create a new constant, and assign it a unit.