Shore power: 30A vs 50A
30 amp is one 120V leg. 50 amp is two 120V legs. Half the coach dead on a 50 amp rig? One leg is probably missing.
The short version
- 30A: one hot, one neutral, one ground. About 3,600 watts total.
- 50A: two hots, neutral and ground. About 12,000 watts total.
- Check the pedestal first. Campground power is the problem more often than you'd think.
- Adapters (dogbones) and cord ends heat up and melt when connections are loose.
On the job
- Meter the pedestal before you plug in: hot to neutral 120, hot to ground 120, neutral to ground about 0.
- 50 A: both hots 120 to neutral and 240 between them. 0 between them means both terminals are on the same leg.
- Look at the plug and inlet blades for heat. A darkened neutral blade on a 50 A plug is an open neutral waiting to happen.
- Under load, meter at the panel: under about 104 V is a problem for the ACs and the converter.
Numbers
- Good shore voltage: about 108–132V
- 50A hot to hot: about 240V
- 30A max: ~3,600W
- 50A max: ~12,000W
- 30 A: 3,600 W total
- 50 A: two 120 V legs, 12,000 W total
- Low voltage: under about 104 V under load
Shop tip
A burnt or discolored plug blade means a loose, high-resistance connection. Replace the end, don't just clean it.
Try it on a service call
Put the lesson to work on a hands-on troubleshooting case.
Keep going on 120V and shore power
Learn it
Prove it
- Half the coach is dead
- Bathroom outlets are dead
- Lights surge and the microwave died
- Shocked at the door handle