Am I hearing things?

craigl59
248 posts                                                                         08-03-2018 10:36am

Since there are electricians seeing this thread would like to ask them if 12/2 Romax is OK for 20 amp circuits. Is there some reason why 10/2 seems to be preferred in many audiophile installations? Is it the concept of "Overwire and Underbreaker?"

Per NEC (National Electrical Code) #12 copper wire is the bare minimum wire size for a 20 amp branch circuit. NEC does not prohibit using a wire size larger than #12. Usually a larger wire size is used for VD (Voltage Drop) that may occur on the conductors of the branch circuit due to the connected load. The connected load does not need to be a continuous connected load. It could be caused by a fluctuating load.

The size of the breaker, overcurrent device, dictates the ampere rating of the branch circuit. The OP has a 30 amp breaker, therefore the circuit is 30 amps. Per NEC you can not install a 20 amp rated receptacle on a 30 amp branch circuit. Per code the breaker must be 20 amp.

Here is an old Link, but still holds true for when a breaker is supposed to trip if overloaded.
https://goodsonengineering.com/wp-content/uploads/2017/08/CircuitBreakerMyths_web.pdf

Thanks jea48.

To add some perspective to Jim’s (Jea48’s) good comments about voltage drop, if the wiring that was replaced is say 50 feet long and during dynamic peaks the current drawn by the system (and anything else that is connected to the corresponding outlets) is say 8 amps (corresponding to about 1000 watts; the aforementioned Bryston amp alone can draw considerably more than that at max power), the change from 12 gauge to 10 gauge will increase the voltage provided to the amp and any other components that are not powered by the regenerator by about 0.5 volts.

That doesn’t seem like a lot, but I suppose it might make some difference sonically. On the other hand, though, if the line voltage at the OP’s location is already particularly high, and perhaps above what is sonically optimal for the particular amp (for example, in terms of the resulting internal temperatures), I wonder if the increase might be in the wrong direction.

In any event, in addition to Jim’s suggestion about obtaining a polarity checker, it may be informative if the OP were to obtain a multimeter and measure the line voltage at various times of the day and evening.

Regards,
-- Al

Craig most 20 amp breakers are run with 12/2 or 12/3  it's hard enough to wire a receptacle with 12 doing it with 10 is a real pain. My guess is unless you're standing there watching the electrician and you had him run 10 he pigtailed some 12 in the box to wire up the receptacle. 

Thanks djones51 and almarg -- this is very helpful perspective and should inform those on Audiogon who are in the process of configuring their systems.