1ph 25kvaTransformer & Equip.Grounding

[dougk]

I am building a glass melting furnace using molybdenum elements. </font>

• <font size="2" face="Verdana, Helvetica, sans-serif">SINGLE Phase. 12kva max.draw.</font>

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• <font size="2" face="Verdana, Helvetica, sans-serif">My path is:</font>

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• <font size="2" face="Verdana, Helvetica, sans-serif">240v Service Entrance, 200A main breaker>></font>

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• <font size="2" face="Verdana, Helvetica, sans-serif">60A breaker>></font>

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• <font size="2" face="Verdana, Helvetica, sans-serif">Separate enclosure mounted, 200A electro-mechanical safety contactor(plenty oversize, new surplus welding contactor)>></font>

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• <font size="2" face="Verdana, Helvetica, sans-serif">Semiconductor-fused 80A Watlow SCR(in the same enclosure)>></font>

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• <font size="2" face="Verdana, Helvetica, sans-serif">Sorgel 25S3H Transformer, 240/480 high to 120/240 low. LVA 208.></font>

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• <font size="2" face="Verdana, Helvetica, sans-serif">120v to my elements, which are wired in series.</font>

<font size="2" face="Verdana, Helvetica, sans-serif">My first ground will run from the entrance grounded neutral directly to the transformer case ground lug. </font>

• <font size="2" face="Verdana, Helvetica, sans-serif">A second ground wire will run from the entrance to the SCR.</font>

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• <font size="2" face="Verdana, Helvetica, sans-serif">I am running a separate 120v line to the enclosure to drive the fan and the safety cut-off relay. I am in and out of the furnace constantly so I will have a mechanical switch operating the safety mechanical relay whenever I open the furnace door. (Actually, I am using a 24vdc relay to switch the 120v to the safety contactor)</font>

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• <font size="2" face="Verdana, Helvetica, sans-serif">I was going to ground the enclosure using this 120v wire run.</font>

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• <font size="2" face="Verdana, Helvetica, sans-serif">I need to ground the furnace structure itself too.</font>

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• <font size="2" face="Verdana, Helvetica, sans-serif">Can I run the ground from the furnace to the transformer lug or does it have to go straight to the service entrance?</font>

<font size="2" face="Verdana, Helvetica, sans-serif">Thank you.

 

[charlie]

Re: 1ph 25kvaTransformer & Equip.Grounding

I removed this post in error. Please continue with my apology. Thank you, Charlie

 

[ron]

Re: 1ph 25kvaTransformer & Equip.Grounding

You can surely utilize the equipment ground conductor run with the power, either an actual conductor or properly installed metallic raceway, to perform most of your grounding concerns. In addition, the transformer will get a grounding electrode conductor, as it is a separately derived source, run back to the grounding electrode system.