A friend and I have differing opinions about what happens when a conductor is oversized for a particular application. This question is not to find out what the proper size of wire to use for an application. Let's say that a circuit requires 14AWG wire conductors but instead 4AWG is used. Would this oversizing of conductors affect the load in any way? The question would apply to a section of water pipe that is oversized. Say that a 100 foot run of pipe was to be all done in 3/4" pipe, but instead 2" pipe were used. I would contend that there would we no detrimental effect. One water drop in, one out the other end. With no drop in pressure from one end to the other. Back to electrical. One electron in one out the other end. As long is you are oversizing and not undersizing.
This would apply if you were wanting to use existing wiring that was for a larger ampacity load for a new device that would otherwise require a new electrical run. Example would be to power an outlet for a microwave or any other light load with old wiring going to an air conditioning unit. Say 6AWG downsized at the outlet to 10AWG or whatever is required for the terminals.