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Generator ground rods?
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by G4AON on August 17, 2006
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Some of the suggested earthing instructions I've found on the web mention that a portable installation should use an 8 foot earth rod of at least a 1/2" diameter. This would appear to be completely over the top, I've never seen anyone using a portable generator with this amount of earthing. Given that the output of my Yamaha EF2800i is floating with respect to earth (UK model), isn't this earthing requirement a bit over the top? The Yamaha manual doesn't give earth rod details, except to mention the earth wire thickness...
What do others use for earthing?
Thanks for your feedback
Dave
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RE: Generator ground rods?
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by KC8VWM on August 17, 2006
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um.. I use an aluminum tent peg? :)
Grounding is a necessary safety feature in case an internal short develops and the electricity ends up on the generator chassis.
Ouch!
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RE: Generator ground rods?
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by KE4SKY on August 18, 2006
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from the National Electrical Code
702.10 Portable Generator Grounding
A new section clarifies the grounding requirements for optional standby systems, when used as a separately derived systems or nonseparately derived system.
Comment:
The Article 100 definition of a Separately Derived System is “A premises wiring system whose power is derived from a battery, from a solar photovoltaic system, or from a generator, transformer, or converter windings, and that has no direct electrical connection, including a solidly connected grounded circuit conductor, to supply conductors originating in another system”.
If the generator transfer switch does not transfer the neutral, the generator is not a separately derived system and the generator grounded conductor (neutral) is not bonded to the generator frame. Small portable generators with receptacles mounted on the generator typically have the grounded conductor (neutral) bonded to the generator frame and cannot be used with a solidly grounded neutral service (due to parallel paths for neutral current and shock hazard).
Chapter 8 Communications Systems
Article 800 Communications Circuits
Article 820 Community Antenna Television and Radio Distribution Systems
800.40(A)(4) [Cable and Primary protector Grounding] Length
820.40(A)(4) [Cable and Primary protector Grounding] Length
New text requires the primary protector for telephone and coaxial cable systems to be “as short as praticable”
Comment: The distance between the primary protector and the bonding point to the electrical system grounding system needs to be kept to a minimum to prevent a difference of potential in the event of an over voltage from lighting or line surges. If a separate grounding electrode is installed at the primary protector location, then it must be bonded to the electrical grounding system with a 6 AWG copper conductor (minimum).
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RE: Generator ground rods?
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by WA4MJF on August 18, 2006
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We use a 4 foot ground rod with the gensets
for W4EOT and the neutrals in the trailer
"float", ie hooked together, but not to
anything else. Also, 4 foot ground on trailer
frame.
73 de Ronnie
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RE: Generator ground rods?
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by K2GW on August 18, 2006
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I use a 3 foot length of ground rod with my Honda EU2000i in the field. It takes just a minute to drive it in and provides reasonable protection. A three foot ground rod in the ground and attached to the generator does a much better job than an eight foot one left at home. ;-)
The Honda also has a floating ground like your Yamaha. The instructions from the NEC are for powering premises wiring with a generator connected to a transfer switch.
73
Gary, K2GW
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RE: Generator ground rods?
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by G4AON on August 18, 2006
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Thanks for the feedback, it's always nice to know what others use. I have an 8 foot earth rod at home, one of those two piece rods that seem beefy enough to earth the power station let alone my house.
For portable use I have a four foot rod, however in several hill top locations the soil is fairly thin and will only allow me to hammer it some 2 feet into the ground. I suppose 2 feet is better than no earth. So far I've always managed to recover it!
73 Dave
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RE: Generator ground rods?
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by KE4DRN on August 18, 2006
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hi,
Remember to have a Vise-Grip or equal locking pliers
so you can twist the groundrod up out of the ground
when you're finished using the genset.
I also have a 3' copper clad rod for genset use.
73 james
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RE: Generator ground rods?
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by KB1LKR on August 19, 2006
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Does NEC, or other, address grounding of mobile generators, e.g. service/utility trucks/vans, motor homes, TV sat. trucks, e-comm trucks/trailers, trailer mounted generator sets, etc.? Presumably these are connected to the vehicle's chassis/frame, but, barring driving a rod, the vehicle (assuming rubber tired not metal tracked) is pretty effectively isolated from the earth for safety grounding purposes.
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RE: Generator ground rods?
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by WA2QIC on August 21, 2006
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For grounding a genset in a temporary setting such as Field Day, I use a 4ft 3/8 th's diameter copper ground rod at the genset, AND at the rig. I have also used a galvanized steel 14" tent peg in a pinch, and once I used a tire lug-wrench, but I think the 4 footer copper rod is the better ground. If you don't ground an a/c genset, you could pass significant a/c hum/noise on your transmissions (not to discount the risk of shock by not grounding) depending on the quality/age of the genset.
As far as sinking an 8ft rod....I wouldn't want to be the one to remove a "temporary" 8ft 1/2" rod. Yikes!
KE4DRN is right - make sure you have adequate tools to remove the rod when the time comes.
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RE: Generator ground rods?
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by WB6BYU on August 21, 2006
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The one time I was with a group using one of the little
DC+inverter generators we had to ground it to reduce the
RF noise that otherwise wiped out all our receivers.
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