Neutral overheating.

[nizak]

Here’s what I’ve got .

2 identical commercial toasters 1800 watt 120V

These toasters run from 7 AM until 9 PM seven days a week.

A month ago I replaced both cord ends and receptacles. One unit is already showing signs of a burnt neutral on both the male blade and the receptacle slot.


The other appears to be perfectly normal in operation.

Each device is in its own 4” sq box with a dedicated 20 amp circuit.

Any thoughts on why the neutral is failing?
Why isn’t the ungrounded side failing?

Would hard wiring and installing a switch be an option?

Would a twist lock device be better?
Any suggestions appreciated.

 

[ruxton.stanislaw]

Here’s what I’ve got .

2 identical commercial toasters 1800 watt 120V

These toasters run from 7 AM until 9 PM seven days a week.

A month ago I replaced both cord ends and receptacles. One unit is already showing signs of a burnt neutral on both the male blade and the receptacle slot.


The other appears to be perfectly normal in operation.

Each device is in its own 4” sq box with a dedicated 20 amp circuit.

Any thoughts on why the neutral is failing?
Why isn’t the ungrounded side failing?

Would hard wiring and installing a switch be an option?

Would a twist lock device be better?
Any suggestions appreciated.

I used to test these all day long. If you want to engineer a switch upstream of the toaster, a standard light switch is always going to be hot with that constant load. I would recommend using a heavier duty 30A switch or contactor. It will last forever that way.

Twist lock will be more reliable. If using a standard NEMA 6-20R receptacle, I recommend to use hospital grade receptacles for heavy loads as the manufacturing and QA processes tend to have more precise standards. You will feel the tighter fit when you plug in to the socket; a better connection is being made between the plug blades and terminals inside the outlet.

 

[augie47]

If one were to be "picky" you would be altering the appliance, however, you could change the plug and receptacle to a 30 amp. A lot more contact area and tighter fit.

 

[Fred B]

What are the voltages at the unit burning out?
What is the wire condition at the breaker?
A weak or bad neutral connection will create an overvoltage over current condition but not trip the breaker.
A Neutral that is multi splice both on same phase will burn it out too.

 

[Frank DuVal]

He says the neutral damage is at the plug/receptacle, not in the building wiring. Something not tight is usually the cause. I agree, best plugs and receptacles of 20 amp or go to 30 amp if the toasters never move from that spot.

 

[synchro]

...
A month ago I replaced both cord ends and receptacles. One unit is already showing signs of a burnt neutral on both the male blade and the receptacle slot.
..
Any thoughts on why the neutral is failing?
Why isn’t the ungrounded side failing?

Is the neutral blade on the plug nickel plated? If so, perhaps there could be a higher contact resistance on the neutral connection ... maybe because of dissimilar metals in the plug and socket, fretting corrosion of the nickel due to vibration or other movement of the contacts, etc. Just throwing out some possibilities.