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Novamill not grounded properly

Posted: Thu 19 Mar , 2009 16:58 pm
by boots
I have a customer whose students are getting shocked by touching the table that a Nova Mill is sitting on. I am curious as to how the AC neutral and the Ground get to / through the transformer and how the grounding should be connected to the machine. I don't have any diagrams to assist me in helping the customer locate test points for troubleshooting this problem. Can you send me schematics, or maybe verbally tell me what to check/test?

Posted: Thu 19 Mar , 2009 16:59 pm
by boots
Here is the link to the Denford Forum with the Novamill Wiring diagrams.

viewtopic.php?t=1834

Posted: Thu 19 Mar , 2009 17:00 pm
by boots
Thank you.
I have these schematics, I was needing something that deals with the 'step up' transformer, ground, earth ground, and how these continue to the machine. For example, does the "ground" from the wall oulet continue (as the same)..to the "ground" that is inside the Nova Mill and/or the control panel.?

Posted: Thu 19 Mar , 2009 17:02 pm
by boots
The ground wire goes from the wall outlet to the Transformer box ground connection, to the Control Box ground connection, through the 40-pin umbilical, to the machine cabinet ground connection. The ground wire is usually a green/yellow striped wire that is connected to the cabinets(s). You may need to look for a wire that has rubbed against something and has worn through the insulation.

Posted: Thu 19 Mar , 2009 17:03 pm
by boots
fixed
the ground was being lost at the outlet - I replaced the outlet and attached an additional ground line to help. interesting to note that if the ground is not making proper contact that the table can get 117 v potential-- could this be because the transformer is not using a center tap ground???- this is a concern I would think--- Earth ground requirement maybe??

Does the config of the step up transformer have anything to do with this issue? Grounded center tap?