Non separately derived system grounding

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cppoly

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Anyone know what is the code section for a non-separately derived system (generator on a 3-pole transfer switch, not switching the neutral) that says making a grounding connection at the generator is not allowed?

What happens if you DO make a grounding connection here?
 
cppoly said:
Anyone know what is the code section for a non-separately derived system (generator on a 3-pole transfer switch, not switching the neutral) that says making a grounding connection at the generator is not allowed?

What happens if you DO make a grounding connection here?
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there is no prohibition on having a GE anywhere. it just has to be connected to the EGC and not the grounded conductor.
 
petersonra said:
there is no prohibition on having a GE anywhere. it just has to be connected to the EGC and not the grounded conductor.
Click to expand...

I thought neutral to case connections were not allowed anywhere other than the service equipment or at a separately derived service. If a generator is not a separately derived service (for instance it is connected using a 3-pole ATS that does not switch the neutral), wouldn't connecting it to a earth via an EGC not be allowed?
 
cppoly said:
I thought neutral to case connections were not allowed anywhere other than the service equipment or at a separately derived service. If a generator is not a separately derived service (for instance it is connected using a 3-pole ATS that does not switch the neutral), wouldn't connecting it to a earth via an EGC not be allowed?
Click to expand...

Didn't Bob say you COULDN'T connect the neutral (grounded conductor) to earth :?
 
petersonra said:
smaller ones usually are.
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Which is why you are almost forced to implement them as SDS with switched neutrals if there is a transfer switch involved, since you are given that option.
The practical dilemma comes when the generator has an internal ground-neutral bond and also has a GFCI-protected output with EGC.
 
GoldDigger said:
Which is why you are almost forced to implement them as SDS with switched neutrals if there is a transfer switch involved, since you are given that option.
The practical dilemma comes when the generator has an internal ground-neutral bond and also has a GFCI-protected output with EGC.
Click to expand...

most of those bonds can be undone though. its just a wire on a screw.
 
cppoly said:
Anyone know what is the code section for a non-separately derived system (generator on a 3-pole transfer switch, not switching the neutral) that says making a grounding connection at the generator is not allowed?

What happens if you DO make a grounding connection here?
Click to expand...
A grounding connection means what?
If you are asking what about connecting to an electrode then there is nothing wrong with this and some generators have an external lug for a connection to an electrode no matter if it is being installed as a SDS or a NON-SDS.

If you are asking about bonding the neutral to an electrode or the supply side bonding at the generator then there will be a parallel path for the return current. Article 250.35 permanently installed generators was introduced in the 2008 code cycle and the bonding conductor between the generator and the transfer was referred to as the equipment bonding conductor.

On a NON-SDS the neutral is bonded at the service and on a SDS the neutral is bonded at the generator. It is not bonded at both places.

Depending on the type and size of the generator and the rules adopted by your state the installation instructions included with the listing of the generator come into play. If this is a generator that is portable and is being connected by a cord plugged into a receptacle on the frame of the generator then UL FTCN states that it must be installed as a SDS.

This category covers internal-combustion-engine-driven generators rated 15 kW or less, 250 V or less, which are provided only with receptacle outlets for the ac output circuits. The generators may incorporate alternating- or direct-current generator sections for supplying energy to battery-charging circuits.
When a portable generator is used to supply a building or structure wiring system:
1. The generator is considered a separately derived system in accordance with ANSI/NFPA 70, "National Electrical Code" (NEC).
2. The generator is intended to be connected through permanently installed certified transfer equipment that switches all conductors other than the equipment grounding conductor.
3. The frame of a certified generator is connected to the equipment-grounding conductor and the grounded (neutral) conductor of the generator. When properly connected to a premises or structure wiring system, the portable generator will be connected to the premises or structure grounding electrode for its ground reference.
4. Portable generators used other than to power building or structure wiring systems are intended to be connected to ground if required by the NEC.
Click to expand...

Article 250.34 states that portable generators are not required to have an electrode system if the adhere to the conditions outlined in 250.34(A)(1) and (2)
 
jwelectric said:
A grounding connection means what?
If you are asking what about connecting to an electrode then there is nothing wrong with this and some generators have an external lug for a connection to an electrode no matter if it is being installed as a SDS or a NON-SDS.

If you are asking about bonding the neutral to an electrode or the supply side bonding at the generator then there will be a parallel path for the return current. Article 250.35 permanently installed generators was introduced in the 2008 code cycle and the bonding conductor between the generator and the transfer was referred to as the equipment bonding conductor.

On a NON-SDS the neutral is bonded at the service and on a SDS the neutral is bonded at the generator. It is not bonded at both places.

Depending on the type and size of the generator and the rules adopted by your state the installation instructions included with the listing of the generator come into play. If this is a generator that is portable and is being connected by a cord plugged into a receptacle on the frame of the generator then UL FTCN states that it must be installed as a SDS.



Article 250.34 states that portable generators are not required to have an electrode system if the adhere to the conditions outlined in 250.34(A)(1) and (2)
Click to expand...


Thank you
 
George Stolz said:
I wonder how long that's been in the white book? No time to research this morning, but I am reminded of this thread ( http://forums.mikeholt.com/showthread.php?t=97685 ) where Honda directs us to remove the bonding jumper when the generator neutral is not switched...?
Click to expand...

Without research and only by memory I think it was somewhere around the 02 code cycle.
Many jurisdictions do not require equipment to be listed in order to be connected to a premises wiring system therefore we have things such as was posted in that thread.

Also things that are listed can be installed in a noncompliant manner. Take a 4 square box that has a UL mark on it. Can it be installed in a wet or a hazardous location? It is UL listed is it not?

90.1 (A) of the NEC is a very important section even though it is not an enforceable section, The purpose of this Code is the practical safeguarding of persons and property from hazards arising from the use of electricity.

These portable generators have never been designed to be connected to a premises wiring system during bad weather. They were designed to be used as temporary power not as an optional standby system as we have tried to use them
 
Massachusetts deals with the problem via an additional exception to the 2011 NEC 702.11. Because of the prevalence of small portable generators being used to provide back-up power to homes via Gentrans-type switches (no breaking of the neutral conductor) they came up with a few conditions under which this is an acceptable installation.
They must be smaller (under 15 Kw) and cord-and-plug connected. There is a limitation on the length of the flexible cord, 15', and the inlet box must be within 10' of the premises main bonding jumper. Clearly they are trying to keep the parallel path short and under control.
 
If the path is parallel and the frame of the generator is involved, the electrical system is connected to earth and someone touches the frame while standing on the ground that the generator is sitting then would there be a third parallel path?

Do the receptacles on the generator meet the requirements of 406.9(B)?

Seems like Massachusetts doesn?t like their citizens very much.
http://www.usfa.fema.gov/citizens/co/generator.shtm
 
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