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[Stephen Kirby]

Tom, is there a need to calculate wire size to the stage?  It's not a voltage drop issue but is there an impedance issue?  Again trying to relate Guy's points to higher frequency but much lower power electronic applications.  My initial guess would be that as long as it is sufficient to carry the fault current which wouldn't be any greater than what is on the supply side.  But it seems things change in high power applications.

Planning ahead for next summer when I'll have another trailer stage in the dirt.  No genny, it's run off 150' of 6/4 and a CA plug on a nearby building.  Figuring that I should connect my distro chassis to the stage just to make sure they're at the same potential.

[Mike Sokol]

Almost: 

- Buy a male L5-30 plug, jumper the ground and neutral conductors together using a very short piece of #10 wire inside the plug, insert into the L5-30 receptacle on the generator.  This bonds the ground and neutral, which ensures GFCI devices and circuit breakers will work as intended.

- Get a 2' piece of grounding rod, a clamp, and a short piece of green stranded #10 wire.  Pound ground rod in ground (depending on the area, you may need to have the utility locator out to make sure you're not going to hit anything with your ground rod), or attach #10 wire to existing unpainted metal - bike rack, water hydrant, etc.  Attach the other end to the ground terminal on the generator.  If the stage is metal, you should really find a way to bond the stage to your generator ground, too.

- Set generator to "120V Only" mode.

- Get two inline GFCI devices like these: http://www.amazon.com/TRC-26020008-6-Shockshield-Protected-3-Outlets/dp/B000HHQIK2 and plug them into the two NEMA 5-20 receptacles on the generator.

- Divide the load between the two circuits.  I would probably put the mains and subs on one circuit and the monitors, lights, and stage power on the other.


For a somewhat larger system you might need to be a little more careful and creative, but for your example system, the above is more than adequate, doesn't require modifying the generator, and provides the best balance of safety vs. hassle.  No 200lb transformer is required.

Yes, that covers the basics.

First: Make sure your generator's Neutral is Bonded to its chassis "Ground". The easiest way to test to see if your generator already has a Bonded Neutral is with a 3-light outlet tester. Here's a video I did about this for the RV industry. If you're using a Honda or Yamaha 2KW or 3KW generator, then you KNOW it has a floating neutral. The easiest way to bond the neutral on one of these small/portable inverter generators is with a plug that has the neutral screw connected to the ground screw with a short length of heavy wire. And yes, if you have a metal stage. you'll want to bond that to the generator frame as well. https://www.youtube.com/watch?v=M-bTLdMjuqU

Second: Earth-ground your generator's chassis via its "ground" lug. I usually use at least two ground rods 4 ft long if there's no chance of hitting anything underground, but a pair of 2 ft ground rods should suffice as long as you're in moist soil. I usually dump a gallon a water around this temporary ground rod just for giggles. Yes, you could pee on it to decrease the ground impedance, but don't most people think we're animals already? So stick to a few jugs of water.

Third: Provide GFCI protection for the backline power. Inline GFCI cords work well, or you can have your stage distro wired with GFCI receptacles. Use individual GFCI protectors on the ends of the distro, rather than a single GFCI feeding a lot of gear. Ground fault currents are additive and can cause nuisance trips, so far better to use separate GFCI's for front-line and back-line power. That way one leaky old fender amp won't bring down the entire stage power system. And use heavy extension cords for long runs. So 12-gauge wire on a 15-amp circuit may not be required by code, but it will make for a stiffer supply that won't droop under load. I use 10-gauge cords for long runs of 20-amp circuits, and that can reduce voltage drop by 30% or so. 

Fourth: Don't allow musicians to use stage amps with broken off ground plugs on their power or extension cords. Instead, use the proper DI box with a pin-1 ground lift to stop hums and buzzes.

Fifth: Be extra safe and use a NCVT (Non Contact Voltage Tester) such as a Fluke VoltAlert or Klein NCVT-1 to check mics and instruments for any significant voltage above earth potential. (A standard 90 to 1,000 volt NCVT will trigger around 40 volts when held close to anything with a few square inches of surface area) The first time an NCVT lights up when you point it at a bass player's amp will amaze you. BTW: I've had musicians cut the green EGC/Ground wire inside of the chassis of their amplifier, so don't trust a ground plug on a stage amp 100%.

Sixth: Take all reports of feeling a shock seriously. Shocks should NEVER happen on a properly powered and grounded stage. If someone reports feeling a shock, get out your voltmeter and find out why. The life you save could be your own.

[TJ (Tom) Cornish]

Not doubting what you are saying at all.

I've never seen anybody do that before in a similar situation.

Jamin, this world is unfortunately murky due to two different typical uses for generators such as the EU series: home backup power and portable power.  If Honda made a bonded generator with GFCI receptacles on the frame, it would be plug and go (plus the ground rod).  Unfortunately Honda hasn't done this, and their current products - the new EU7000 included - are more geared toward the home backup application where a second ground -> neutral bond would be detrimental, and the belief that an unbonded system offers some isolation benefits.

Electrical safety is a continuum.  I believe what I have proposed is the safest method for use with the EU6500 as it accounts for nearly all electrical failure modes with minimal effort and expense, and does not require modifying the generator, so can be used with rented equipment.  I'm very confident that lots of people use EU6500s by just plugging and going - that is Honda's intent with the product after all; however there are demonstrable holes in that plan, depending on what else is wrong.

[TJ (Tom) Cornish]

Tom, is there a need to calculate wire size to the stage?  It's not a voltage drop issue but is there an impedance issue?  Again trying to relate Guy's points to higher frequency but much lower power electronic applications.  My initial guess would be that as long as it is sufficient to carry the fault current which wouldn't be any greater than what is on the supply side.  But it seems things change in high power applications.

Planning ahead for next summer when I'll have another trailer stage in the dirt.  No genny, it's run off 150' of 6/4 and a CA plug on a nearby building.  Figuring that I should connect my distro chassis to the stage just to make sure they're at the same potential.

I have not researched this issue specifically so I reserve the right to be corrected, but as long as the ground connection has a sufficiently low impedance to trip the largest breaker in use, you will have covered the general intent of the ground fault path.  This should be roughly parity with your supply wiring - i.e. if #12 wire offers an acceptable voltage drop for the distance, a #12 ground wire should be OK too.

If you're using GFCIs for all stage power like you should be, any connection at all should be sufficient to exceed the 5mA trip current of a GFCI device; and this is where the real safety benefits come from.

[Mike Sokol]

I have not researched this issue specifically so I reserve the right to be corrected, but as long as the ground connection has a sufficiently low impedance to trip the largest breaker in use, you will have covered the general intent of the ground fault path.  This should be roughly parity with your supply wiring - i.e. if #12 wire offers an acceptable voltage drop for the distance, a #12 ground wire should be OK too.

To be accurate, you're not talking about the earth ground connection, which will typically be around 25 ohms or even higher in dry/sandy soil. You're referring to the EGC (Equipment Grounding Conductor) which must have a low-impedance path back to the power source Ground-Neutral bonding point. Note that without a Ground-Nuetral bond there's no path for the GFCI to get its imbalance current, and without an earth ground connected to this G-N bonding point, the GFCI won't trip if you're in the fault path. However, in that case you probably won't be shocked, you'll just raise the potential of your local ground plane to above earth potential. Not a good thing...

[TJ (Tom) Cornish]

To be accurate, you're not talking about the earth ground connection, which will typically be around 25 ohms or even higher in dry/sandy soil. You're referring to the EGC (Equipment Grounding Conductor) which must have a low-impedance path back to the power source Ground-Neutral bonding point. Note that without a Ground-Nuetral bond there's no path for the GFCI to get its imbalance current, and without an earth ground connected to this G-N bonding point, the GFCI won't trip if you're in the fault path. However, in that case you probably won't be shocked, you'll just raise the potential of your local ground plane to above earth potential. Not a good thing...

Correct - talking about the ground wire between the distro and the stage and not the dirt. 

[Guy Holt]

..the above is more than adequate, doesn't require modifying the generator, and provides the best balance of safety vs. hassle.

Since when is it permissible to trade off safety for convenience? Safety always comes first.  Here are a few of the things an electrical inspector will have issues with how TJ has traded off safety for convenience.

Almost: 

- Buy a male L5-30 plug, jumper the ground and neutral conductors together using a very short piece of #10 wire inside the plug, insert into the L5-30 receptacle on the generator.  This bonds the ground and neutral, which ensures GFCI devices and circuit breakers will work as intended.

- Get a 2' piece of grounding rod, a clamp, and a short piece of green stranded #10 wire.  Pound ground rod in ground (depending on the area, you may need to have the utility locator out to make sure you're not going to hit anything with your ground rod), or attach #10 wire to existing unpainted metal - bike rack, water hydrant, etc.  Attach the other end to the ground terminal on the generator.  If the stage is metal, you should really find a way to bond the stage to your generator ground, too.
 

According to Article 250.4 (5) "Effective Ground-Fault Current Path," of our National Electrical Code (NEC) requires that the grounding system create "a permanent, low-impedance circuit capable of safely carrying the maximum ground-fault current likely to be imposed on it...." The operative words here are “permanent”, “low-impedance”, and “capable.”  What TJ is suggesting does not meet this definition.

“permanent”: Code compliant bonding of the Neutral of a portable generator to its' frame is not as simple as putting an external jumper between the ground and neutral of an open receptacle as TJ suggests here. A twist-lock plug end that can be mistakenly removed or not fully engaged if not twisted does not meet the definition of permanent.  I have had electrical inspectors kick my ground clamps to make sure that they are permanent.

 “low-impedance”: The prescribed impedance of Earth Ground according to the NEC is 25 Ohms.  It usually takes a 10’ rod, and sometimes two, to get 25 Ohms to ground. It is highly unlikely that TJ’s 2’ rod will provide a code compliant ground.

“capable”: Jumping between the ground and neutral of an open receptacle as TJ suggests here will not likely meet the Code requirement of  "capable of safely carrying the maximum ground-fault current likely to be imposed on it” because  it is not a ‘listed” piece of equipment for that purpose.

In open frame models, like the ES6500, you can simply add a Neutral Bond jumper from one of the generator winding leads to the frame (as pictured above.) In an EU series inverter generator, bonding the Neutral to Ground requires removing the main panel and inverter module to get behind the breakers, switches, sockets etc. - not easily done or undone. According to the Honda Service Bulletins, it should only be done by a qualified Honda service technician.

The Neutral/Ground bond in a generator is not something to be taken lightly because in a double fault situation like that illustrated above, the two faults create a 240V exposure plus a current path resulting in Electrocution. For this reason it is critical that GFCIs be used effectively and that they operate reliably.  What TJ proposes below is not the most effective use of GFCIs under the circumstances. Mike has partially addressed why in his post above.

Get two inline GFCI devices like these: http://www.amazon.com/TRC-26020008-6-Shockshield-Protected-3-Outlets/dp/B000HHQIK2 and plug them into the two NEMA 5-20 receptacles on the generator.

No 200lb transformer is required.

For the record, a 7.5kVA transformer which is sufficient for a 60A circuit does not weigh 200lbs.

Guy Holt, Gaffer
ScreenLight & Grip
www.screenlightandgrip.com

[TJ (Tom) Cornish]

Since when is it permissible to trade off safety for convenience? Safety always comes first.  Here are a few of the things an electrical inspector will have issues with how TJ has traded off safety for convenience.

According to Article 250.4 (5) "Effective Ground-Fault Current Path," of our National Electrical Code (NEC) requires that the grounding system create "a permanent, low-impedance circuit capable of safely carrying the maximum ground-fault current likely to be imposed on it...." The operative words here are “permanent”, “low-impedance”, and “capable.”  What TJ is suggesting does not meet this definition.

“permanent”: Code compliant bonding of the Neutral of a portable generator to its' frame is not as simple as putting an external jumper between the ground and neutral of an open receptacle as TJ suggests here. A twist-lock plug end that can be mistakenly removed or not fully engaged if not twisted does not meet the definition of permanent.  I have had electrical inspectors kick my ground clamps to make sure that they are permanent.

 “low-impedance”: The prescribed impedance of Earth Ground according to the NEC is 25 Ohms.  It usually takes a 10’ rod, and sometimes two, to get 25 Ohms to ground. It is highly unlikely that TJ’s 2’ rod will provide a code compliant ground.

“capable”: Jumping between the ground and neutral of an open receptacle as TJ suggests here will not likely meet the Code requirement of  "capable of safely carrying the maximum ground-fault current likely to be imposed on it” because  it is not a ‘listed” piece of equipment for that purpose.

In open frame models, like the ES6500, you can simply add a Neutral Bond jumper from one of the generator winding leads to the frame (as pictured above.) In an EU series inverter generator, bonding the Neutral to Ground requires removing the main panel and inverter module to get behind the breakers, switches, sockets etc. - not easily done or undone. According to the Honda Service Bulletins, it should only be done by a qualified Honda service technician.

The Neutral/Ground bond in a generator is not something to be taken lightly because in a double fault situation like that illustrated above, the two faults create a 240V exposure plus a current path resulting in Electrocution. For this reason it is critical that GFCIs be used effectively and that they operate reliably.  What TJ proposes below is not the most effective use of GFCIs under the circumstances. Mike has partially addressed why in his post above.

For the record, a 7.5kVA transformer which is sufficient for a 60A circuit does not weigh 200lbs.

Guy Holt, Gaffer
ScreenLight & Grip
www.screenlightandgrip.com

Guy,

You can take up your angst with Honda, not me.  They have created a UL-listed product that lives in the gray area between the NEC, OSHA, and UL rules.  I wish it was internally bonded with GFCIs onboard, but it isn't.
 
It's all well and good to climb on a high horse and toot a "safety at all costs" horn, but that isn't reality in many situations.  Have you ever tried to pull even a 2' ground rod out of the ground much less a 4' or 8' ground rod?  Are you proposing that people take apart rented generators to install a bond?  I would rather give people a $10 removable solution that is effective than have people give up and use the generator stock, and a 2' ground rod that might actually be used rather than an 8' ground rod that requires renting a back hoe to remove.  When and if your transformers become standard issue at equipment rental houses we can talk about whether that is theoretically better or not (I still believe it isn't, all things considered).  Until then, I would rather have a practical solution that solves the practical issues than a theoretical one that is unavailable. 

If the inspector doesn't like the "temporary bond", you are free to "temporarily unbond" it.

[Guy Holt]

I would rather give people a $10 removable solution that is effective ... and a 2' ground rod that might actually be used rather than an 8' ground rod that requires renting a back hoe to remove.

A "solution" that won't pass inspection is not a solution.  Here is a tip for removing 8' ground rounds.  Grab the top with a pair of channel locks and twist back and forth. You will now be able to pull even an 8' rod out with ease - no back hoe required.

Guy Holt, Gaffer
ScreenLight & Grip
www.screenlightandgrip.com

[Jonathan Johnson]

Here is a tip for removing 8' ground rounds.  Grab the top with a pair of channel locks and twist back and forth. You will now be able to pull even an 8' rod out with ease - no back hoe required.

That's not so easy in rocky soil. When driving rods in rocky soil, they tend to bend, and bent rods don't twist very well -- or pull out easily.

Whatever happened to Mike's "bed of nails" idea?

[ProSoundWeb Community]