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H. Bunch · Apr 13, 2006, 05:22 PM

I just bought a 4400/3500 watt generator for a building project. The directions say that I need to ground the generator with a suitable grounding rod and stranded No. 12 AWG wire. I have never heard of contractors grounding their generators. Are they being careless, or are my generator instructions overly cautious (like when they tell you not to stand on the open oven door!)?

tkrussell · Apr 13, 2006, 05:50 PM

That's correct, most people do not properly ground their portable generators as per code and manufacture's instructions.

Of course, because of product liability, manufacturer's will tend be cautious, if someone gets hurt, and there is an injury, they will be off the hook if the unit is not grounded per their instructions and per code.

When we do events such as festivals, outdoor shows , etc. we must always ground all the portable gensets brought in for the event. If you go to a carnival, take a look at the generaotrs , and you will see them grounded to rods.

Chances of something happening while you are using a small genset is unlikely, but you assume all risk.

H. Bunch · Apr 14, 2006, 04:23 AM

Well, I sure do appreciate your input! It is good to know the facts.

So, do you drive in 8'copper or brass rods to ground them? Would a shorter rod do? Also, doesn't the generator ground itself as its metal body touches ground?

tkrussell · Apr 14, 2006, 12:02 PM

Purchase an 8 foot ground rod, it is made with a copper tube with soft white metal inside. I do not se brass rods made any longer.

Code requires a full eight foot, so as to achieve a max of 25 ohms.

No, just because the unit sits on the ground does not mean it is properly grounded properly, plus considering the unit is painted and usually has rubber feet.

hamaso · Sep 13, 2011, 03:21 AM

Hey Bunch,
Generator room is to have a separate main earth bar, to which the Generator Neutral (star point) is to be connected by insulating earthing conductor through the neutral earth link or device. Neutral earthing conductor is to be sized to carry maximum earth fault current for time it takes the system protection to operate, with final conductor temp not exceeding 160 C (but not less than 120 mm2 for ratings below 500 kVA and 300mm2 for higher ratings unless otherwise specified).
Generator Earthing terminal is to be connected to the generator main earth bar by insulated copper conductor of csa (not less than 120 mm2 unless otherwise specified).
Switchgear (ATS) and control gear earthing terminals are to be connected by separate protective conductor to respective normal or emergency main distribution board earth bars.

hamaso · Sep 13, 2011, 03:25 AM

Hey Bunch,