Portable generator question

[T.M.Haja Sahib]

QUOTE=Bernard1599;1338646]

What is it, exactly, that makes the above a safe installation with the neutral-to-frame connection at the generator? I
[/QUOTE]

Perhaps to avoid damage to the generator from any incoming over voltage transient between neutral and EGC.

 

[tkb]

Please do not take the following questions as being adversarial in nature, but??

I don't see how I can. This was an informational post and only shows the MA NEC amendment on the grounding of portable generators.

702.11. Insert a new 702.11(C) as follows:

(C) Classification of Supply. A generator with a grounded circuit conductor connection as part of its output shall be wired as a separately derived source unless its grounded circuit conductor is not bonded to the frame, or where used to supply a premises wiring system it shall be permitted to be wired as a nonseparately derived source if all of the following conditions are met:

(1) The generator rating does not exceed 15 kw.

(2) The generator is connected through a flexible cord and a cord connector to a flanged inlet.

(3) The flexible cord does not exceed 4.5 m (15 feet) in length.

(4) The flanged inlet connection point is not more than 3.0 m (10 feet) from the main bonding jumper or system bonding jumper for the supplied premises.

(5) The point of connection is marked ?Disconnect cord when generator is not in service.?

(6) Ground-fault protection of equipment has not been installed on any portion of the premises wiring system supplied by the generator.

Informational Note: Current product standards require all portable generators rated 15 kw and below and supplying grounded output circuits to have the grounded circuit conductor connections bonded to the generator frame.

Please do not take the following questions as being adversarial in nature, but??

What is it, exactly, that makes the above a safe installation with the neutral-to-frame connection at the generator? Is it the fact that the flexible cord and the inlet box wiring combined length is 25? or less from the MBJ and not say 30??; or is it the fact that there is no GFP for equipment and not GFP for personnel?; or is it that the genny is 15kw or less?; or etc.? Why does the combination of 1 through 6 make this a safe use of a portable generator used to power the structured wiring.

Regards,
Bernard

I don't see a problem with this since that generators this size have been connected this way in emergency situations for years without problems.
This requirement prevents the uninformed from making modifications to the portable generator (by trying to disconnect the neutral to ground connection) that would make it unsafe and void the listing if used as a stand alone generator in other situations since I am sure the modifications won't get reversed when the generator is disconnected.

By connecting the portable generator in the manner that MA allows, the connection is code compliant, safe and the listing of the generator in not compromised.

Remember, this is a temporary portable connection and not a permanently connected generator installation.

 

[Bernard1599]

Thank you Tim.

 

[kwired]

I personally do not see a problem with having all portable generators regardless of size having the XO terminal unbonded to generator frame. If connecting to a premesis wiring system you have to have an equipment grounding conductor from the premesis wiring to the generator - this is bonded to the neutral at the service equipment - that will bring the generator frame to the same potential as the rest of the premesis equipment grounding conductors.

If you are using the generator stand alone (not connected to premesis wiring) bonding the generator frame does not accomplish much. There is no reference to ground unless you install a grounding electrode How many times have you ever seen a grounding electrode for a portable generator that was not supplying premesis wiring? When you take your small generator to a job where there is no power do you drive a ground rod and connect it to your generator? Some people may but I am guessing almost all instances there is no grounding electrode.

Now lets assume the XO is bonded to the generator frame. Most portable generators either have rubber feet or rubber wheels. There is still no ground reference if no grounding electrode is installed, if one of the other system conductors should fault to ground you will have a shock hazard between grounded objects, earth and the generator frame.

A floating ground on a portable generator is just fine. You have an ungrounded system. Once one conductor faults to ground you have a grounded system although unintentional. It will work safely and will not even be noticed that it is faulted. If a second system conductor becomes faulted to ground then the overcurrent protection does its job. GFCI's can still be used if desired. If they do operate something has to be faulted someplace and then a second fault would have to occur otherwise there will never be any unbalanced current to ever trip the GFCI.

 

[jwelectric]

The original post asked a question about a generator that has not been answered yet. He asked about the neutral and equipment ground bond at the generator frame.

This question has nothing to do with Article 702 nor 250 but instead is addressed in Section 100.3(B)

(B) Installation and Use. Listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling.

Any and all equipment must be installed with any instructions included in the listing and labeling of the equipment including generators. UL has included these instructions in FTCN of the White Book.

ENGINE GENERATORS FOR PORTABLE USE (FTCN)
GENERAL
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 Listed transfer equipment that switches all conductors other than the equipment grounding conductor.
3. The frame of a Listed 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.

I would say that this generator is required to be installed as a SDS and the transfer switch MUST switch the neutral conductor as pointed out in the listing of the generator.

 

[Bernard1599]

The following wiring diagrams are taken from an online pdf manual of a GenTran manual transfer switch for use with a portable generator up to 7500 watts. The first shows a conceptual scenario portable genny placement, power inlet, etc. relative to the panel location. The second shows a wiring diagram of the xfer switch. The connection to the premises wiring system in this instance is as a SDS, yet the utility and genny neutrals are not switched. There is no mention in the online manual of removing the genny neutral-to-ground bond. The manual states that the transfer switch is both UL listed to UL standard 1008 and NEC 702.6.

I have looked also at 200 amp transfer switches for 20kw whole house generators and I cannot see on the wiring diagrams any provision for switching the neutrals.

After reviewing several of these manuals, there does not seem to be any pointed emphasis or provisions for switching the neutrals in a SDS. Why would the manufacturer not be concerned with any liability issues? There must be thousands and thousands of these small portable generators connected to premises wiring systems throughout the US without switching the neutrals or removing the N-G bond. What do you all think about this?

Bernard

 

[jumper]

What do you all think about this?

Bernard

I think that you will never get a straight 100% answer, I have searched and there many opinions.

Drives me bonkers.

 

[jwelectric]

There must be thousands and thousands of these small portable generators connected to premises wiring systems throughout the US without switching the neutrals or removing the N-G bond. What do you all think about this?

Bernard

Some of the things I have wondered about;
The millions of homes out there that have knob and tube wiring methods still in use, millions of homes that has no devices anywhere protected by ground fault, kitchens wired with size 14 conductors, the hundreds of thousands with split phase panels and the list go on and on.

Isn?t change wonderful?
Because of change we have not only GFCI but AFCI and even out buildings that have an equipment grounding conductors installed to them.

I don?t recon that anyone would be liable for the way things were done in the past if it was compliant at the time but I still wonder.

 

[Bernard1599]

The following is from a Honda owners manual:

Honda portable generators have a system ground that connects
generator frame components to the ground terminals in the AC output
receptacles. The system ground is not connected to the AC neutral
wire. If the generator is tested by a receptacle tester, it will show the
same ground circuit condition as for a home receptacle.[/I][/B]

Hondas are wired differently than most others that I have read about. They also recommend Reliance, GenTran or APC transfer switches. There is still no mention of switching neutrals when connecting to the premises wiring.

Have any of you here connected portable generators to premises wiring? If so, how did you handle the bonding and switched neutral issues?

I don't mean to run this into the ground, But I really would like to understand what the more "generator experienced" people here do to try to insure that the installation is safe.

Regards,
Bernard

 

[jwelectric]

I have installed a few generators in my life time. I have never installed anything such as discussed here simply because of the dangers in using these generators that are not listed to be exposed to inclement weather such as rain, snow, and ice. The wiring is not enclosed in weather proof enclosures and the devices do not have in use covers. They were designed to be used on clear days and kept dry not sit in snow and ice of exposed to the rain.

Then there is the problem with fueling the generator should the power be out for an extended period of time. Most have the tank mounted where filling it exposes everything to spilled fuel a fire hazard.

 

[stickboy1375]

Then there is the problem with fueling the generator should the power be out for an extended period of time. Most have the tank mounted where filling it exposes everything to spilled fuel a fire hazard.

They have a warning of a cool down period before refueling.

 

[Bernard1599]

I have installed a few generators in my life time. I have never installed anything such as discussed here simply because of the dangers in using these generators that are not listed to be exposed to inclement weather such as rain, snow, and ice. The wiring is not enclosed in weather proof enclosures and the devices do not have in use covers. They were designed to be used on clear days and kept dry not sit in snow and ice of exposed to the rain.

That is true. They are not to be run in wet or inclement weather as shown in the following typical warning included in all portable generators as far as I have read.

- DO NOT operate generator in rain or wet weather.

On the types that you have installed directly to premises wiring, how did you handle the switched neutral and bonding issue?

Regards,
Bernard

 

[jwelectric]

That is true. They are not to be run in wet or inclement weather as shown in the following typical warning included in all portable generators as far as I have read.

- DO NOT operate generator in rain or wet weather.

On the types that you have installed directly to premises wiring, how did you handle the switched neutral and bonding issue?

Regards,
Bernard

The generators that I have installed for dwellings were enclosed and installed as a non-SDS. The smallest I have installed was a 9000 watt LP unit with a Generac 8 circuit transfer switch. It was hard wired and not cord and plug connected. This customer tells me all the time that they wished they had went with a bigger unit.

As you posted, I have always pointed out that the self-contained units were not approved to be used in bad weather and therefore useless for an optional standby system during ice and rain storms. I always try to point my customers to safety for them and never put a dollar ahead of their safety.

 

[Bernard1599]

NEC 2008 Article 100 Definition of a Separately Derived System and the April 11, 2008 White Book, page 134, ENGINE GENERATORS FOR PORTABLE USE (FTCN) 2. Listed transfer switch that switches all conductors other than the egc.

Unless I am missing something in the wiring diagrams or schematics of the TSs that I have looked at, I could not find a single phase transfer switch, whether service rated or not, that has a provision for switching the grounded conductor in a residential application.

I would venture to say that 99% of all residential single-phase generators connected to the premises wiring system of US residences are non-compliant installations because of un-switched neutrals.

Can this be correct?

Regards,
Bernard

 

[hillbilly1]

NEC 2008 Article 100 Definition of a Separately Derived System and the April 11, 2008 White Book, page 134, ENGINE GENERATORS FOR PORTABLE USE (FTCN) 2. Listed transfer switch that switches all conductors other than the egc.

Unless I am missing something in the wiring diagrams or schematics of the TSs that I have looked at, I could not find a single phase transfer switch, whether service rated or not, that has a provision for switching the grounded conductor in a residential application.

I would venture to say that 99% of all residential single-phase generators connected to the premises wiring system of US residences are non-compliant installations because of un-switched neutrals.

Can this be correct?

Regards,
Bernard

With a manual transfer switch, all that is needed is a three pole switch, which is easy enough to get, the third pole on the switch does the switching. I not believe there is a requirement that the neutral must be broken before the hots, only at the same time. That being said, the majority of single phase manual transferswitches sold in the US are two pole only. If you have a generator that has built in ground fault protection, it will not work well with a two pole switch.

 

[jwelectric]

The electrical inspector will only look at the point where the generator is being connected to the building to the required transfer switch if the generator and cord is not present during his/her inspection.

Should the portable generator being attached to this male plug meet the requirements of a non-SDS then there is nothing wrong. These generators will most commonly be a tag-along or something that hooks to the back of a tractor or mounted on a vehicle.
Portable generators was first mentioned in the 2002 code cycle in Part III 702.10 where it clearly states that a portable generator that is being used as an optional standby system has to be connected to earth one way or the other. Being installed as a SDS then an electrode as outlined in 250.30 must be installed.

UL in their listing information clearly states that should one such as a pictured be connected to the premises wiring then it must be connected as a SDS and mandates that the equipment grounding conductor be connected to the premises wiring grounding electrode.

As you and others have posted these generators are to be used on clear days and kept out of the rain, snow, ice, mud, ect???.. Then there is the cool down time and waiting for any spilled fuel to dry up that makes using one impractical as an optional standby system.

590 was introduced in the 2005 cycle and has been updated every cycle including some very important information about portable generators.

 

[kwired]

The electrical inspector will only look at the point where the generator is being connected to the building to the required transfer switch if the generator and cord is not present during his/her inspection.

Should the portable generator being attached to this male plug meet the requirements of a non-SDS then there is nothing wrong. These generators will most commonly be a tag-along or something that hooks to the back of a tractor or mounted on a vehicle.
Portable generators was first mentioned in the 2002 code cycle in Part III 702.10 where it clearly states that a portable generator that is being used as an optional standby system has to be connected to earth one way or the other. Being installed as a SDS then an electrode as outlined in 250.30 must be installed.

UL in their listing information clearly states that should one such as a pictured be connected to the premises wiring then it must be connected as a SDS and mandates that the equipment grounding conductor be connected to the premises wiring grounding electrode.

As you and others have posted these generators are to be used on clear days and kept out of the rain, snow, ice, mud, ect???.. Then there is the cool down time and waiting for any spilled fuel to dry up that makes using one impractical as an optional standby system.

590 was introduced in the 2005 cycle and has been updated every cycle including some very important information about portable generators.

I have a portable generator and have needed it for standby power a couple times, once for 10 days. I have a few points to make and don't care if they are right or wrong.

1. The ice storm was over when I needed the generator, the next 10 days were nothing except cold. If it were going to rain I could put a canopy over it. In cold weather it needs to be in a warm space anyway otherwise the carbuerator ices up and it doesn't run so well. (evaporating fuel is a cooling effect and humidity in the air condenses and freezes in the carbeurator, just blocking air flow some keeps enough heat around the unit to prevent this from happening)

2. When the generator ran out of fuel it was plenty cooled down by the time I made it out to refuel it.

3. I don't need power constantly or for that matter at all but is a nice convenience to have.

4. The generator frame is not bonded to the generator neutral. By running a neutral and an equipment grounding conductor to the premesis wiring the frame becomes bonede through the system bonding jumper at the service.

5. You don't even want to know what kind of homeowner generator setups I encountered during this same time on my service calls, or how much damaged equipment I ran into because they did not know what they were doing.
Whether or not the frame of the generator is bonded or not was not a top concern with some of these places, althouth it would have prevented equiment being burned up in a few cases even though the EGC would have been carrying neutral current. I still would rather see them burn up equipment than electrocute themselves though.

 

[hillbilly1]

Back during hurricane Fran, I believe it was, I hooked up a large generator to power an Orange box. People were lining up around the parking lot to get generators to power their houses. After they sold out, some of them came back with issues with the new generators not starting or other problems. Since they were sold out, and didn't have any to replace the "defective" generators, I started helping the customers with their generators, most of them the problem was the low oil cut off, the factory had not put quite enough oil in them. topped off the oil, cranked them and sent them on their way. A couple of guys brought one back (a very expensive 7 or 8 kw model) saying they ran one tank of gas thru it, filled the gas and OIL back up, then it would not crank. These boys were about three sheets in the wind when they turned the generator over on it's side and filled it all the way up with oil! Took the air cleaner off, and oil oozed out of the carb. Drained the oil down to where it was supposed to be, put in a new plug and air filter and sent them on their way!

 

[kwired]

Back during hurricane Fran, I believe it was, I hooked up a large generator to power an Orange box. People were lining up around the parking lot to get generators to power their houses. After they sold out, some of them came back with issues with the new generators not starting or other problems. Since they were sold out, and didn't have any to replace the "defective" generators, I started helping the customers with their generators, most of them the problem was the low oil cut off, the factory had not put quite enough oil in them. topped off the oil, cranked them and sent them on their way. A couple of guys brought one back (a very expensive 7 or 8 kw model) saying they ran one tank of gas thru it, filled the gas and OIL back up, then it would not crank. These boys were about three sheets in the wind when they turned the generator over on it's side and filled it all the way up with oil! Took the air cleaner off, and oil oozed out of the carb. Drained the oil down to where it was supposed to be, put in a new plug and air filter and sent them on their way!

I have not seen any gasoline engine powered equipment that comes shipped with engine oil in the crankcase. They usually do have oil separately packed in the box and the user must add it before using. I suppose it is possible they maybe did not put enough oil in there to start with, like maybe they had a run of products where they supplied the wrong bottle of oil.

 

[hillbilly1]

I have not seen any gasoline engine powered equipment that comes shipped with engine oil in the crankcase. They usually do have oil separately packed in the box and the user must add it before using. I suppose it is possible they maybe did not put enough oil in there to start with, like maybe they had a run of products where they supplied the wrong bottle of oil.

Maybe they do it differently in your part of the country, but I have not seen anything that does not come with the oil already in it here, this includes pressure washers, lawnmowers, ect. All of the Generac Guardian generators arrived at our warehouse full of oil. Now the larger generators do not come with oil, but is added by the startup mechanic.