Discuss Glue Guns Failing earth continuity test in the Electrical Testing & PAT Testing Forum area at ElectriciansForums.net

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Hi Guys

Long time since I last posted but I have a problem I'm stuck on.

My company uses a few industrial hand held glue guns.

We have been experiencing repeated problems where the glue gun is failing on the earth continuity test. (Full test every 3 months)

Typically 0.26 - 0.56 ohms.

We have opened the glue guns up and the earth reading is fine on the cable entering the glue gun.

It is the short section of internal earth wire that is bolted to the body of the heating element that is failing.

I'm guessing as it's connected to the hot body (190 degrees Celsius) that it may be causing the copper to degrade.

The only exposed metal part is the tip (we clean this thoroughly before testing).

We have experienced the same problem on different glue guns, it seems to be an inherent design flaw.

Has anyone else experienced this problem, as i'm guessing it must be a common problem.

Does anyone have any solutions apart from replacing the internal earth wire every 3 months?

Can anyone suggest a replacement glue gun that doesn't have this problem (They are high power ones typically 300-500w).

I was hoping I could find a class II one no luck and doubt they exist.

Any suggestions would be appreciated.

Thanks
Nick
 
It's probably the contact between the jumper wire terminal and the heater body. Is that aluminium by any chance? What resistance readings are you getting, typically?
 
a bit of copper grease where the termination internally is made to the hot body might help.
it is probably corrosion causing the poor reading.
 
It's probably the contact between the jumper wire terminal and the heater body. Is that aluminium by any chance? What resistance readings are you getting, typically?
Yes it is aluminium.

0.56 typically
[automerge]1571910461[/automerge]
a bit of copper grease where the termination internally is made to the hot body might help.
it is probably corrosion causing the poor reading.
I can try it and see if it helps thanks
 
Yes it is aluminium.

0.56 typically
[automerge]1571910461[/automerge]

I can try it and see if it helps thanks
Try cleaning the connections may be corrosion due to dissimilar metals touching each other, worth a try.
 
Hmm, connections to hot aluminium are notoriously unreliable unless very well engineered. You'll probably find if you can flex or disturb the connection to break through the oxide layer, the resistance will fall temporarily. Possibly a design flaw. Can you post a pic of the connection?
 
Hi,is the connection via a machine screw and eyed terminal?
If there is room,you could swap this for a same sized stud and nut,then fix the terminal with a second nut. I have done this in the past,with upvc welding gear,and used stainless,even accepting the issues disimilar metals can bring.
 
I would try carbon grease on the terminations, as others have pointed out dissimilar metals reacting will cause poor continuity results.

Have you spoken to the glue gun manufacturers?

Nice to see someones actually testing properly, well done.
 
Hmm, connections to hot aluminium are notoriously unreliable unless very well engineered. You'll probably find if you can flex or disturb the connection to break through the oxide layer, the resistance will fall temporarily. Possibly a design flaw. Can you post a pic of the connection?
I will ask the maintenance electricians to get a picture in the morning as they are planning on replacing the wire (again)

Thanks
Nick
[automerge]1571928886[/automerge]
Hi,is the connection via a machine screw and eyed terminal?
If there is room,you could swap this for a same sized stud and nut,then fix the terminal with a second nut. I have done this in the past,with upvc welding gear,and used stainless,even accepting the issues disimilar metals can bring.
That's a great idea.

I think it might me a self tap screw and ring terminal.
But I'm sure we could do something similar to what you suggest to stop the ring terminal being in contact with the aluminium providing there is room in the case.

Thanks
Nick
[automerge]1571929196[/automerge]
I would try carbon grease on the terminations, as others have pointed out dissimilar metals reacting will cause poor continuity results.

Have you spoken to the glue gun manufacturers?

Nice to see someones actually testing properly, well done.
My only concern about putting carbon grease / copper slip on the connection is how might it react to the heat (190C).

I actually sent the glue gun back to the manufacturer who reported that there wasn't a fault and suggested there was something wrong with my pat tester (seaward Apollo 500) as it tested ok using theirs.
On return from the manufacturer it tested ok, but 3 month later it has failed again.

Thankyou I was tasked with getting a new pat test system and software up and running and training the apprentices it's been a challenge but we are trying our best to do it right!!!
 
Last edited:
My only concern about putting carbon grease / copper slip on the connection is how might it react to the heat (190C).
A very light smear is all that is needed between components, the rest can be wiped off once the terminations are tightened.
 

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