While servicing a "World Dryer Corp" washroom hand dryer, I have come across what I believe to be the worst earth bonding arrangement for the front cover imaginable.

The cover (diecast metal) just locates into place, and "earthing" is provided by the clip shown in the picture, which locates onto the spigot on the cover.

As can be seen both the clip and cover have corroded, making this earth bonding arrangement totally ineffective in my opinion. The clip even falls off the cover spigot, so not even any pressure there.

Even cleaned up, and the clip tension restored, I would not be happy with this earth bonding at all.

What do you guys think ?

 

Is there additional grounding of the panel?

I don't have the specific UL standard to work with but if this falls under the UL Ground continuity test the low-current DC resistance from the panel to the AC supply ground connection should measure <1 ohm. Can you measure it?


THE DIFFERENCE BETWEEN GROUND CONTINUITY TEST AND GROUND BOND TEST, TECOTEC
https://www.tecotec.com.vn/en/news/...n-ground-continuity-test-and-ground-bond-test

World Dryer Recalls to Repair Hand and Hair Dryers Due to Electric Shock Hazard
https://www.cpsc.gov/Recalls/2007/w...-and-hair-dryers-due-to-electric-shock-hazard

Recall: World Dryer Recalls to Repair Hand and Hair Dryers Due to Electric Shock Hazard
https://recalls.justia.com/household-and-office/hair-dryers/08-531/

Report here --> https://www.saferproducts.gov/

 

Certainly the corrosion can be prevented by covering the clip and the attachment point with a small dab of anti-corrosion grease, possibly even :"NoALOX", although of the die-cast front is not aluminum that is not the best choice. The more expensive option is a closed-loop crimp on lug on some internal bolt. But if the whole product is snap together, (Designed for assembly), that may not be an option.
For the existing unit, a simple check with the ground integrity test of an appliance tester machine will verify either pass or fail. It measures the voltage drop of the safety ground connection at several amps of current.

 

Is there additional grounding of the panel?

No, the cover simply ledges onto the plastic sub-frame. They have provided this (IMHO) poor connection simply because it is the external shell of the product, and therefore should be bonded to earth.

I don't have the specific UL standard to work with but if this falls under the UL Ground continuity test the low-current DC resistance from the panel to the AC supply ground connection should measure <1 ohm. Can you measure it?

At the moment the clip won't even stay put on the "spigot" it is supposed to be grounding, it just falls off. So a "measurement" is impossible.

THE DIFFERENCE BETWEEN GROUND CONTINUITY TEST AND GROUND BOND TEST, TECOTEC
https://www.tecotec.com.vn/en/news/...n-ground-continuity-test-and-ground-bond-test

I would say this is "bonding" of the essentially isolated metal front casing, as a "just in case" scenario. Although in this case, totally ineffective.

World Dryer Recalls to Repair Hand and Hair Dryers Due to Electric Shock Hazard
https://www.cpsc.gov/Recalls/2007/w...-and-hair-dryers-due-to-electric-shock-hazard

Recall: World Dryer Recalls to Repair Hand and Hair Dryers Due to Electric Shock Hazard
https://recalls.justia.com/household-and-office/hair-dryers/08-531/

Both of the recalls refer to a different model

 

Certainly the corrosion can be prevented by covering the clip and the attachment point with a small dab of anti-corrosion grease, possibly even :"NoALOX", although of the die-cast front is not aluminum that is not the best choice. The more expensive option is a closed-loop crimp on lug on some internal bolt. But if the whole product is snap together, (Designed for assembly), that may not be an option.
For the existing unit, a simple check with the ground integrity test of an appliance tester machine will verify either pass or fail. It measures the voltage drop of the safety ground connection at several amps of current.

I will just clean it up (to bare metal), and re-tension the clip so it snaps into place. I can see no other way to bond the outer case to the internal grounding stud. Ease of assembly/disassembly was the original design, so will have to go with that. I don't think it's ideal, but that's the way it was designed..