Bit Bucket
Brookings, Oregon
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Salvo wrote:No, my logic is OK, at fault may be your reading comprehension. Did I say GFCI should not be used? Let's not get silly.
Bit Bucket wrote:Salvo wrote:$hit happens. Perhaps you need to get better informed.
As opposed to your previous post I will provide a link.
http://onwatergarden.com/others/cgfirecall.htm
Bit Bucket wrote:
Most (if not all) modern GFCI's will fail in a way that does not pass power.
So a manufacturer of one GFCI makes a faulty product and you dismiss GFCI's?
So you don't drive a car either, right? There have been certain brands and models of unsafe cars.
I'm sure we can find examples of shoddy housing developments too, so you will have to give up living in a house as well.
Your logic is interesting...
You don't seem to have a point or anything to contribute.
The goal for some of us is to try to get to the bottom of things with knowledge and logic and try to come out on the other side better for it. It seems to me this is not your goal at all.
You are obviously trolling...
Good day to you.
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vermilye
Oswego, NY, USA
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I don't know if this will help or add more confusion, but this is my understanding of the rather complex requirements for bonding generators:
Other than lightning protection, one major reason for bonding in a utility supplied system is that it is already bonded by the utility. They bond at most transformers to prevent a transformer fault from producing high voltages to the household wiring. The utilities also sometimes use the earth as one of the wires in a high voltage distribution system which establishes a bond. Unless you use an isolation transformer, it is impossible to run a utility supplied system that does not have one side of it tied to the earth. There will always be a potential difference between one of the hots & the earth.
If you tie a generator into a household system, a bond already exists at the building's service entrance. Since it is important to prevent current in the ground wiring (which may include everything bonded to it such as your plumbing, heating ducts, even the water in your plastic pipes) the service entrance bond is only one allowed - you cannot also include one at the generator because that would be paralleling the current carrying conductor (the neutral) with the ground.
This means that a home stand by generator that ties into the household wiring cannot have an internal bond.
If the system does not tie into an existing system in most cases the frame of the generator can serve as the grounding electrode, that is you do not need to drive a ground rod each time you set up your generator (and there are good, although controversial reasons not to).
As to bonding of one of the current carrying conductors to the generator frame, it gets interesting.
First, a 120V only system does not have a neutral as defined by the NEC. Because of this there is no requirement that one of the legs be tied (bonded) to the frame of the generator.
The ground is connected to the generator frame. Although there is no NEC requirement for bonding since there is no neutral, there are some exceptions, some required by OSHA, not the NEC. For example, if the generator produces over 5KW, capacitive coupling between the generator windings & the case is high enough to form an effective, but high impedance bond which could present a shock hazard since a fault might not draw enough current to trip the generator's breaker. In this case a physical bond is required to provide a low impedance bond.
To avoid the requirement of adding a GFCI to the generator, OSHA requires that the current carrying wires must not connect to the generator frame. This means that a 120v generator without a GFCI cannot bond one of the conductors to the frame. Technically, you are violating OSHA regulations when you bond your inverter generator to make your EMS work.
In a split phase generator (120/240V) there is a neutral and bonding of the neutral to the generator frame is required by both the NEC & OSHA. This is to prevent the possibility of a 240V shock hazard caused by two faults - one leg shorted to the generator frame & the other leg shorted to the load case (which could be the frame of your RV). This would produce 240V between the load case & the earth (since the generator frame is sitting on the ground).
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Bit Bucket
Brookings, Oregon
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vermilye wrote:I don't know if this will help or add more confusion, but this is my understanding of the rather complex requirements for bonding generators:
Other than lightning protection, one major reason for bonding in a utility supplied system is that it is already bonded by the utility. They bond at most transformers to prevent a transformer fault from producing high voltages to the household wiring. The utilities also sometimes use the earth as one of the wires in a high voltage distribution system which establishes a bond. Unless you use an isolation transformer, it is impossible to run a utility supplied system that does not have one side of it tied to the earth. There will always be a potential difference between one of the hots & the earth.
If you tie a generator into a household system, a bond already exists at the building's service entrance. Since it is important to prevent current in the ground wiring (which may include everything bonded to it such as your plumbing, heating ducts, even the water in your plastic pipes) the service entrance bond is only one allowed - you cannot also include one at the generator because that would be paralleling the current carrying conductor (the neutral) with the ground.
This means that a home stand by generator that ties into the household wiring cannot have an internal bond.
If the system does not tie into an existing system in most cases the frame of the generator can serve as the grounding electrode, that is you do not need to drive a ground rod each time you set up your generator (and there are good, although controversial reasons not to).
As to bonding of one of the current carrying conductors to the generator frame, it gets interesting.
First, a 120V only system does not have a neutral as defined by the NEC. Because of this there is no requirement that one of the legs be tied (bonded) to the frame of the generator.
The ground is connected to the generator frame. Although there is no NEC requirement for bonding since there is no neutral, there are some exceptions, some required by OSHA, not the NEC. For example, if the generator produces over 5KW, capacitive coupling between the generator windings & the case is high enough to form an effective, but high impedance bond which could present a shock hazard since a fault might not draw enough current to trip the generator's breaker. In this case a physical bond is required to provide a low impedance bond.
To avoid the requirement of adding a GFCI to the generator, OSHA requires that the current carrying wires must not connect to the generator frame. This means that a 120v generator without a GFCI cannot bond one of the conductors to the frame. Technically, you are violating OSHA regulations when you bond your inverter generator to make your EMS work.
In a split phase generator (120/240V) there is a neutral and bonding of the neutral to the generator frame is required by both the NEC & OSHA. This is to prevent the possibility of a 240V shock hazard caused by two faults - one leg shorted to the generator frame & the other leg shorted to the load case (which could be the frame of your RV). This would produce 240V between the load case & the earth (since the generator frame is sitting on the ground).
Very well put. I am finding the same thing:
NEC 2011
250.34(C)
Art 100 Def Separately Derived System.
250.30
250.30(A)
250.20
250.20(B)
551.30(A)
Are the references in question.
So far it has been found that the NEC requires the neutral to be bonded on permanently mounted generators in RV's where the generator operates at over 150 volts.
My Onan 2800 comes with the neutral bonded at the generator, as do the other generators made for permanent mounting in RV's that I know of. My 2800 inverter (made for permanent install) also comes with and recommends that the neutral is bonded (ahead of it's built in transfer switch) as it too is a separately derived system.
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Salvo
California
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Joined: 06/01/2008
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You do have a reading comprehension issue as well as name calling problem.
I suggested to the OP he not bond the generator. The over/under voltage protection may not even work when operating the gen in economy mode. He may need voltage protection at a campground that has inadequate wiring, but doubtful if needed with gen. I would rather be two faults away from electrocution than one fault away.
Sal
Bit Bucket wrote:
You don't seem to have a point or anything to contribute.
The goal for some of us is to try to get to the bottom of things with knowledge and logic and try to come out on the other side better for it. It seems to me this is not your goal at all.
You are obviously trolling...
Good day to you.
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Salvo
California
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Interesting. My memory was a bit off, 5kW is the magic number for bonding.
I didn't think generator capacitor coupling is that great to require bonding @ >5kW. A number of years ago I tested this impedance in my MH. We all know that the voltage between ground and the hot and neutral is about 60V, or half of 120V. The reason we have 60V is because of a capacitive voltage divider. I measured the impedance and determined it was an equivalent 4.7 nF capacitor connecting hot to ground and another capacitance from neutral to ground.
I determined stray capacitance from the Yamaha EF2800i generator added only a fraction to the total capacitance. Most of the capacitance came from the EMI capacitors located at my converter 120V input.
I can only conclude the 5kW gen they say requires bonding has stray capacitive coupling more than 100 times greater than my 2.8kW gen.
Sal
vermilye wrote:
The ground is connected to the generator frame. Although there is no NEC requirement for bonding since there is no neutral, there are some exceptions, some required by OSHA, not the NEC. For example, if the generator produces over 5KW, capacitive coupling between the generator windings & the case is high enough to form an effective, but high impedance bond which could present a shock hazard since a fault might not draw enough current to trip the generator's breaker. In this case a physical bond is required to provide a low impedance bond.
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vermilye
Oswego, NY, USA
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Quote: I determined stray capacitance from the Yamaha EF2800i generator added only a fraction to the total capacitance. Most of the capacitance came from the EMI capacitors located at my converter 120V input.
I can only conclude the 5kW gen they say requires bonding has stray capacitive coupling more than 100 times greater than my 2.8kW gen. One point - the 2800i is an inverter generator - don't know what effect that would have on the winding to frame coupling... In any case, I guess you will have to take that up with OSHA - it is their requirement...
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Salvo
California
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OSHA requirements probably don't even apply for RV use.
Did they expand their domain?
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Wayne Dohnal
Bend, OR.
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Jon - Thanks for adding your understandings to the discussion. Regarding your statement "In a split phase generator (120/240V) there is a neutral and bonding of the neutral to the generator frame is required by both the NEC & OSHA", could you by any chance point me to the article that says the split phase generator has to be bonded, but doesn't also require the grounded conductor in a 2-wire system? When I first started looking at this in the 2005 NEC it was easy to find, but I'm having a hard time with the 2008 and 2011 editions.
Regarding the capacitive coupling in the inverter generator, in my eu2000i the short-circuit current between either hot and frame ground is under 2 mA. It won't even light up an LED.
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MrWizard
Van Nuys, Ca
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Joined: 06/27/2004
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this issue "bonding a portable generator" was discussed ad nausea for weeks in the 3000w Chinese generator forum
with the same results as here
it boils down to the bare facts
that unless you have a driven earth ground and bond Both and the generator frame to grd and rv frame to grd ( against code)
bonding the generator frame makes the rv frame part of the electrical circuit and subject to voltage potential above zero volts earth grd
I will never bond the "supposed" neutral of a 120v portable generator to the generator frame
I would rather be exposed to a capacitance of 60v low current in milliamps than a 120v shock from the generator output
real example here: many times I have used generator powered drills or saws or welder on the RV
if the tool failed and shorted out worn wiring , bad switch etc.. it would be a capactive effect of 60v
with the neutral bonded the voltage between hot and frame is 120v
remember your rv sets on tires, unless connected to shore power the frame is not earth bonded, and even then people get tingled or shocked between bare grd and door handle or steps
WHY. ?
because of voltage difference, improper or in Complete earth bonding on the circuits mean the bonded frame is Not at zero volts
bonding the 'neutral' to generator frame, without providing a solid secure buried earth grd per NEC specs for the generator frame, is not a good idea
your opinion may vary
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Wayne Dohnal
Bend, OR.
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The safety issues of bonding vs. not bonding have very knowledgeable and highly polarized people on both sides of the issue. IMO this indicates that the "facts" are not all that clear cut, and there isn't going to be any agreement in the foreseeable future.
What the code says, for both built-in and portable generators, should be very clear cut, yet every time somebody thinks they have it figured out, somebody else seems to find something to throw it in doubt. The code issue should be answerable. I hope I'm right about this, but could also be wrong.
The fact that it's not spelled out clearly tells me that it's not a major issue. If large numbers of people were getting killed or injured by portable or RV generators, I think the NEC would get updated pretty fast to remove any doubt or ambiguity. For example, there could be a section that clearly spells out the issues in one place, instead of having to comb for the distributed bits and pieces and determining which ones do and don't apply.
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