Jump to content

Measuring Voltage on 50-Amp Plug

Recommended Posts

What voltage should I see when I measure between the four points on a 50-amp plug? If I measure right or left side to neutral or ground, I read 120 volts. If I measure right side to left side, what should I read?

Share this post

Link to post
Share on other sites

Excellent question, as it is a good idea to check before plugging in.

The two outer straights are both hots: L1 and L2.

The center straight is the neutral

The center round is ground


Between either outer straight and center straight or center round= 120 VAC

Between center round and center straight= 0 VAC

Outer straight to outer straight= 240 VAC

Above are the readings for a properly wired 50 amp outlet.

If the two hots L1 and L2 are wired from the same "phase" in the CG main breaker box which is NOT to code, reading from outer straight to outer straight will be 0 VAC. The danger with this is that you could overheat the neutral wire. The neutral wire in a properly wired circuit carries only the DIFFERENCE in amps between L1 and L2. If both hots are on the same "phase", the neutral must carry the SUM of L1 and L2. The neutral wire is not sized for this. If total draw is less than 50 amps (note, there are 100 amps available as L1 is on a 50 amp breaker as is L2) the power can be used with reasonable safety, as the neutral is sized to carry a maximum of 50 amps.


Share this post

Link to post
Share on other sites

Please sign in to comment

You will be able to leave a comment after signing in

Sign In Now

  • Create New...