Current on dryer vent

[Greg1707]

A customer contacted me about their dryer vent. While cleaning the vent the technician was shocked. I checked with a non contact voltage tester and there was indeed current on the vent as well as the dryer frame. I found the cord had been installed incorrectly. The strap from the green screw to the neutral had been removed and the equipment ground on the cord had been connected to the neutral screw. I moved the equipment ground to the green screw and all is well.

So, it appears as it was installed the appliance frame was not bonded. Would we expect the incorrect installtion would lead to current on the frame?

 

[LarryFine]

Would we expect the incorrect installtion would lead to current on the frame?

Voltage, but yes.

 

[electrofelon]

I think there is a problem with the dryer. Bonding will often mask an electrical problem but not solve it and it very well may get worse. You probably have a high impedance fault to the frame.

 

[ggunn]

I think there is a problem with the dryer. Bonding will often mask an electrical problem but not solve it and it very well may get worse. You probably have a high impedance fault to the frame.

Most dryers use 240V P to P for the heating element and 120V P to N for the motor. Voltage on G is to be expected (and undesired) if there is a N - G bond at the dryer.

 

[Dsg319]

Most dryers use 240V P to P for the heating element and 120V P to N for the motor. Voltage on G is to be expected (and undesired) if there is a N - G bond at the dryer.

Shouldn’t it be just the voltage drop along the motor and conductors and minimal at that?

 

[tortuga]

I think there is a problem with the dryer. Bonding will often mask an electrical problem but not solve it and it very well may get worse. You probably have a high impedance fault to the frame.

or a weak neutral on the branch circuit

 

[tallgirl]

or a weak neutral on the branch circuit

There’d still have to be some fault to the frame to get current to flow to ground.

 

[ptonsparky]

I need to see the connections. the description is not clear to me,

 

[electrofelon]

How was

Most dryers use 240V P to P for the heating element and 120V P to N for the motor. Voltage on G is to be expected (and undesired) if there is a N - G bond at the dryer.

But if the neutral is intact and connected, the only voltage to ground would be the voltage drop which is not enough to cause a shock, probably just a few volts. Perhaps OP could clarify how it was connected. If even using a high impedance meter, you measure more than a few volts frame to ground with no EGC connected, you have excessive leakage that needs further investigation.

 

[n1ist]

Where was the white wire connected?

 

[Fred B]

Sounds like someone never changed the outlet and wiring to provide a separate EGC for the dryer, usually not an issue until it is. Appliance likely wired for a 4 wire connection and installer never corrected for that to use the 3 wire cord.

the equipment ground on the cord

That is a common mis identification, The 3rd wire is not a ground conductor on a 120/240V appliance it is the neutral, it has no Equipment ground. So High resistance on the neutral will cause voltage to be present on the appliance frame to a remote ground. Proportional to how high the resistance all the way to being open neutral will have progressively higher voltages. Having the 4th wire and separating the NG at the appliance would sort of share the neutral current until it reached a tripping point of the supplying breaker. GFCI requirement of the newer code would cause this tripping at a much lower level vs a faulted situation.