Information: 1) Electrical engineering degree :) , but not an electrician :( , 2) need help understanding NEC requirements for this application, 3) will have commercial electrician help but want understanding of requirements beforehand, 4) there are no permits, no inspectors, no code requirements in my rural county at this time, I am responsible for not burning my new house down! 5) New construction sized for 200A service, 6) 200A main breaker panel located 15 feet interior of proposed underground service entrance location, 7) Olympian Caterpillar 35kW LP generator to be located on site in existing building. 8) Transfer switch is automatic ASCO 165, 200A rated, but not rated as service entrance equipment.

Now for the rest of the story:
Primary power service runs approx. 1 mile through the woods, I am the only service on the line, i.e. lightning a problem, power outages a problem. Power company has placed ground based transformer within 10 feet of a permanent structural building that will house the standby generator, this building and the transformer are approximately 150 feet from the new house construction. The power company has calculated the need for 250 mil (best) or 4/0 (OK) for the secondary run underground. Problem is with their routine install, with meter base on the exterior of house I would still have to run 150 feet of similar cable for the standby generator and locate the transfer switch at the house. This seems redundant.

I would like to mount the meter base & separate disconnect or better yet a CSED, meter base/service disconnect on the outside of the generator building, along with the transfer switch and then have a single underground run to the house that is 150 feet away.

Questions:
1) Does this make sense, per NEC?
2) If downstream of the service entrance, does the NEC require 3 or 4 conductors to be ran the entire 150 feet to the house?
3) What are the grounding/bonding requirements at each end?
4) Since the meter base and disconnect are 150 feet away, although accessible on the outside of the generator building, is an additional disconnect required at the entry point into the house? Remember the main breaker panel is approx. 15 feet interior.

Thanks for any help, this complexity is a little beyond my residential electrician wiring the house and the power company's advice stops at the meter base.

Regards,
Huck

This plan makes complete sense, and since the utility advice ends at the meter, so does their jurisdiction.

So,
1. Yes.
2. 4 wires from the service entrance Main Disconnect to all points downstream.
3. Grounding the neutral only occurs at the Main Disconnect. This will be with at least one ground rod, maybe more depending on local code. More than one is always better. Only at the Main Disconnect will the neutral, grounding electrode conductor, and equipment grounding conductor connect. From that point on the neutral needs to be insulated and isolated.

This is assuming the ATS will be a 2 pole, and not 3 pole to switch(open) the neutral from the genset. This will be called a NON-Separately Derived System.
4. A 200 amp breaker in the panel is not needed, but can be installed. For conveinence.

For the UG feeder from ATS load side to house panel, use 250 MCM Al for the phase conductors,#4/0 Al for neutral, and #1 Al for equipment ground. Are you planning to use URD direct burial or conduit?


Due to proximity to utility transformer, ask utility for AIC rating of xfer, and confirm the ATS meets or exceeds this rating.

If needed,I can provide a one line diagram.

Thanks TKRussell,

Now that the concept is sound, could we venture a little further with the details. As they say, "the devil's in the details!".

Your questions:
Are you planning to use URD direct burial or conduit? Answer: 3" PVC conduit
Ask utility for AIC rating of xfer, and confirm the ATS meets or exceeds this rating.
Answer: Utility company was provided spec sheet on ASCO switch, was approved by them.
(I have provided you with condensed version of specs on xfer switch, see attached, ASCO 165, 200A, 2-pole, with solid neutral, separate ground, BUT specs says lugs requre copper conductors, that is one of the detail questions below.

NEW INFORMATION:
1) House interior breaker panel is SQD Homeline 200A, main lugs are 250 AL compatible. Not sure we can get that big of cable bent to get in the lugs, but panel states it will accept them! House is on crawlspace, main feed must come up from under house.Thoughts on this??
2) ATS has the following lugs: 200 amp. Transfer Switch power terminals accept wire sizes
one #14 to 4/0 AWG CU (copper only).

NEW QUESTIONS:
1) From your comment of no main breaker needed at interior of house main panel per code, do you also mean there is not a code requirement to place a disconnect at the point the service cable enters the house from underground. The utility main disconnect would be in plain sight of the house approx. 150' away, but if for some godforsaken reason house was on generator power, its main disconnect breaker would not be visible, as it is inside its weatherized housing.

2) I think I am clear on the bonding/grounding. Only at the utility main service disconnect AND/OR meter base, correct?

3) Is any grounding of the main breaker panel inside the house required via ground rods outside the house? Your prior answer would indicate "not neede" as grounding provided via 150ft of separate ground cable from main service disconnect. Just seems a long way away with some earth grounding, but...thats why I asking! Thanks

4) 35kW Genset has separate case ground and neutral terminals. Is is correct that they should remain separate into the ATS and not be bonded together?

5) Following 4) above, should the case of the genset be not only grounded to the ATS ground (not neutral conductor) but also to an earth driven ground rod? Per our discussed layout, the genset will be within 20 feet of the main service disconnect/meter base/ATS, which will all be on the wall of the generator building.

6) On a practical note, if no disconnect box on exterior of home, do you think you can bend, pull, etc, 250 cable in the 3" UG conduit through an LB (pulling bend) at the house where the service cable enters or will some other approved enclosure be required?

7) Per the copper conductor requirement of the ATS (? ) How would you suggest the connection be made to the 250 load cables going underground to the house. I was hoping to be coming directly out of the ATS with 3" conduit and 250 to the house. With the ATS spec of copper only, that sucks.

Thanks, hope this keeps your interest up, I need the help!! Any others opinions, jump right in.

Regards,
Huck

Attached Images

Asco_165_OwnersManual_Condensed.pdf (260.9 KB, 600 views)

Your questions:
Are you planning to use URD direct burial or conduit? Answer: 3" PVC conduit

OK then use the Al wire sizes I mention with XHHW insulation.

Ask utility for AIC rating of xfer, and confirm the ATS meets or exceeds this rating.
Answer: Utility company was provided spec sheet on ASCO switch, was approved by them.

OK

(I have provided you with condensed version of specs on xfer switch, see attached, ASCO 165, 200A, 2-pole, with solid neutral, separate ground, BUT specs says lugs requre copper conductors, that is one of the detail questions below.

I have reviewed the specs, see below for a Al/Cu connector solution.

NEW INFORMATION:
1) House interior breaker panel is SQD Homeline 200A, main lugs are 250 AL compatible. Not sure we can get that big of cable bent to get in the lugs, but panel states it will accept them! House is on crawlspace, main feed must come up from under house.Thoughts on this??

Either use a cable bender, or install a large junction box ( electrician should know how to size this JB)in crawlspace to change over from 250MC Al to either #4/0 Al or #2/0 copper. See hereIlsco - Electrical connectors, compression, taps, splicers, grounding and more:

2) ATS has the following lugs: 200 amp. Transfer Switch power terminals accept wire sizes
one #14 to 4/0 AWG CU (copper only).

Need to use a crimp on connector that converts aluminum conductor to copper, see here:
NEW QUESTIONS:
1) From your comment of no main breaker needed at interior of house main panel per code, do you also mean there is not a code requirement to place a disconnect at the point the service cable enters the house from underground. The utility main disconnect would be in plain sight of the house approx. 150' away, but if for some godforsaken reason house was on generator power, its main disconnect breaker would not be visible, as it is inside its weatherized housing.

"In sight of " rule does not apply to residential main service disconnects. You can have a 200 amp breaker in house panel if you like, but is not necessary.

2) I think I am clear on the bonding/grounding. Only at the utility main service disconnect AND/OR meter base, correct?

Only in the enclosure that contains the Main Service Disconnect, there will be a neutral bar that will connect directly to the enclosure using a jumper or screw, is called the Main Bonding Jumper, and connect the incoming neutral, load neutral, load equipment ground conductor, and grounding electrode conductor.

3) Is any grounding of the main breaker panel inside the house required via ground rods outside the house? Your prior answer would indicate "not neede" as grounding provided via 150ft of separate ground cable from main service disconnect. Just seems a long way away with some earth grounding, but...thats why I asking! Thanks

No additional grounding electrodes are allowed, only at the Main Service Disconnect.

4) 35kW Genset has separate case ground and neutral terminals. Is is correct that they should remain separate into the ATS and not be bonded together?

Correct.

5) Following 4) above, should the case of the genset be not only grounded to the ATS ground (not neutral conductor)

Correct
but also to an earth driven ground rod?

NO GROUND ROD at genset, only at Main Service Disconnect. The genset/ATS is a NON - separately Derived System, and shall not be grounded with it's own grounding electrode, only at Separately Derived Systems, ie; the utility transformer


6) On a practical note, if no disconnect box on exterior of home, do you think you can bend, pull, etc, 250 cable in the 3" UG conduit through an LB (pulling bend) at the house where the service cable enters or will some other approved enclosure be required?

Sure, this is where electricians earn their money doing the bullwork of handling wire.May also look for an oversize LB, called Mogul LB Condulet. Or use a 4 " PVC LB and reducers down to 3" conduit.

However, this may be a good location for the large junction box I mentioned. If outdoors thou, it will need to be RainTight.

By the way, the 3" conduit sweeps in the ground should be rigid steel, otherwise the heavy conductors can "burn thru" the plastic sweeps on such a long pull.

7) Per the copper conductor requirement of the ATS (??) How would you suggest the connection be made to the 250 load cables going underground to the house. I was hoping to be coming directly out of the ATS with 3" conduit and 250 to the house. With the ATS spec of copper only, that sucks.

See my crimp Al/Cu reducer solution above, all the other wiring between the Main, ATS, and Genset can be copper, if you like. Any Al wire connecting to the ATS will need to conversion connectors.

I do need to say, all of this is basic code and your electrician should know all of this, nothing too complex for a qualified electrician. I have no problem answering, that is what I am here for, but you may want to beware of your electrician.

Thanks TK,

Answers have been direct and concise. Going into this little project, just want to be on top of the game. Residential electrician just mentioned the most he had ever installed were the Generac Genpaks 7-16kW units fed by subpanel, nothing whole house as I am discussing. I am having a commercial electrician help me with what you and I have discussed. Just appreciate your opinion so I can speak intelligently with him about the details and especially grounding requirements.

Regards again,
Huck

TKR,

Installation is proceeding per our discussions above with 4 separate conductors to the entrance to the house. Two electricians are doing the work. One the main service from the utility company and generator/ATS equipment to the house, the second, my residential electrian who is wiring the house. Where they meet is still my concern.

The electrician who is wiring the house has installed per my home specification, a 200A 40sp. SquareD Homeline panel with 200A main breaker (as you would know these are the least expensive to purchase as kits with a handful of general breakers). Secondly, he is installing a 200A Homeline disconnect breaker with feedthru lugs and 8sp subfeed on the exterior of the home because he feels code requires it and generally is a good idea because owners like to have access to subfeeds in the future to run spas, outdoor lights, etc, etc.. I have no problem personally with the concept.

Problem may occur as follows. I have examined the Homeline disconnect and the neutral and ground lugs are bonded, as it appears to me, permanently across the top of the panel bus. The neutral lug on this disconnect sits in between the main load lugs and runs under the insulating block to the ground lug.

Therefore since bonded together here, his concept is to just run appropriately sized 3-wire standard service entrance cable from this disconnect on the exterior of the house to the main panel interior to the house approx. 15 feet inside. :confused: What are your thoughts here??

He also says OK to install ground rod outside at disconnect. This is where your specific answer previously clearly stated - NO ground rod. :confused: What are your thoughts here??

:confused: Also, with all the disconnects, what is the proper permanent labeling requirements on the panels (interior main breaker panel, exterior disconnect outside house, combo CSED disconnect/meter base at generator shed 150' away)?

One last question: I noticed you enterained a question recently regarding Arc Fault breakers. I understand code requires them only in bedrooms at present. :confused: Why? Why bedrooms? I don't understand the thinking here? Does arcing somehow occur more frequently in bedrooms?? Or do they think that if fault created fires in other parts of the house give you more time to jump out the window? Remember there is no code inspector in my county.



Thanks
Huck

He "feels" code requires it? Ask him to show you in the code where it requires another main? And to show you about the grounding issue.

As long as there is the main service disconnect at the meter location, another disconnect is not required.There may be one if desired.

However, the disconnect at the house needs the neutral/ground connection broken and the neutral isolated, with 4 wire going into the house panel. There should not be a ground rod at this disconnect. I am sure this connection can be broken. If you give me the model number I can check.

The grounding is done only at the main disconnect at the service meter. He will violate code if he install this ground rod, and does not break connection of the neutral/ground. Not only will code be violated, the grounding will be affected and in the event of a short the main breaker may not trip quick enough.

Every code has a physical or operational reason, nothing is in the code just because someone thinks it should be there.

What do you by labeling? The main breaker at the meter will be called "Service Disconnect". Anything beyond that can be called whatever you like.

Statistics had shown that many fires had been caused by the cords of lamps, alarm clocks, etc, that resides in bedrooms, often left untouched for long periods, and stuck behind furniture. These cords had gotten damaged and frayed, and caused high resistance shorting and arcing, that would not trip standard breakers. Regular breakers would assume the amp draw was just a load. This is what caused NFPA to implement Arc Fault Circuit Interrupters into bedrooms only.

AFCI breakers can be used on any circuit if desired if you chose to spend the money. NFPA took an approach to make bedrooms safer because of people sleeping and not wanting to rely on smoke detectors alone to wake people in the event of an arcing fault, and did not want to create a cost prohibitive situation.

This was the case with GFI when they were first made mandatory, it took several years to add circuits, outlets, and other areas mandatory to be GFI. I expect the same with AFCI protection.

In reviewing articles on the internet involving Section 250 of the NEC, I have seen a couple of posts on other sites that reference the ability to use only 3 conductors (not a separate ground) in similar installations as mine.

The quoted dialog is as follows:
--------------------------------------------------------------------------------
Karl riley05-24-2003, 01:55 PM
One more question. Don, maybe you can tell me this. I was asked to look at a rural installation before the inspector comes out. The meter and main disconnect are on a post about 75 feet from the nearest building. It supplies two buildings. SE cable was used into the main building (two hots, one N, no G). The panel in the building has both neutral and grounding busses, with the bonding screw is turned in on the neutral bus. A bare GEC from the neutral bus goes out of the panel through a concrete wall.

I am assuming that the feed should have been 4-wire and that neutral should be kept insulated from the can, with the GEC originating from the grounding bus. My question is, is there a distance limit for the service entrance post outside of a building?
Karl

Tom baker05-24-2003, 02:03 PM
Karl, there is a difference between the 2002 and 1999 NEC on this issue. A three wire feed to the downstream panel is OK if there are no parallel paths for current flow. Most electricans now use a 4 wire feed and separate the neutral and ground. In Washington State, this is now required by a state code. There is no distance limit from the service to the building (there was a proposal in the 2002 cycle that was rejected, and I believe it is also proposed in the 2005 cycle).

Don_resqcapt1905-24-2003, 07:08 PM
Karl,
Your case is not the same as the first post in this thread. In the first post there is only one building or structure involved and all panels after the service disconnect require a "4 wire" connection. In your case, the pole is a building or structure and it is unlikely that there are additional conductive paths between the pole and the buildings. The code will permit you to use a "3 wire" connection and rebond in this case. See 250.32(B)(2). I see that this is a rural installation. If there are livestock involved, you need to look at Article 547.
Don


Karl riley05-24-2003, 08:05 PM
Good info, Tom and Don. No other metallic paths, so he's OK for inspection. Thanks.
Karl
--------------------------------------------------------------------------------


I am in agreement with your understanding of the NEC requirements for my installation. What do you make of the comments above? Are there any exceptions in the section of code that references the 3-wire installation above as being allowed for new construction? Please address the issue of "3-wire ok, if no parallel paths exist" and differences between the 99 and 02 code.

PS, I visited a friends newly constructed house today in my county and his electrician was there. I asked him to show me how he grounded the system. The layout is similar to mine. Meter base-->Disconnect/subfeed panel outside-->main breaker panel inside. He follows your information exactly, disconnect has utility neutral bonded to enclosure and grounded to ground rod. 4-wire system (H-H-N-G) enters house to main breaker panel and there he breaks the bus that from the factory bonds the neutral to the ground bus. He then bonds the ground bus (not the neutral) to the main breaker enclosure. Therefore keeping grd and neutral totally separate except at the service disconnect outside. Also dryer and range circuits are 4-wire (separate ground). Is this a code requirement now for new construction?

I need to address this with my electrician this week! I just want to make sure I am correct. I know he is using a 3-wire configuration because of two things I see from his rough-in so far. He has added a subfeed panel from downstairs to upstairs which is SEU cable, 3 conductor (therefore no separate ground). There is no separated ground bus in the main panel inside, they are factory bonded together. According to my friend's electrician you have to actually take the neutral bar out and cut it with a saw and install a separate ground lug. This has not been done. And beyond that, 3-wire is what he told me was OK. I feel I need to address this before the installation proceeds too far.

Thanks again

This is not a job, its an adventure...

First, the 2005 edition of the NEC should be in effect thru-out the USA. What state are you in?

This can be reviewed at:

NFPA 70: National Electrical Code®

I will say that you must read the entire Article 250, plus any applicable definitions, Article 100, to understand each section of Art 250. You cannot just jump into the middle.

Second, let me be sure I understand the installation correctly:
Utility transformer-10 feet away is Meter/service disconnect on exterior of structure to house genset/transfer switch-150 feet to main/panel on exterior of house, then to main service panel just inside house.

Grounding the neutral(grounded conductor) shall be done only at the Service Disconnecting means, per NEC Sec 250.24(1).

No connection to ground "shall not be made to any grounded circuit conductor on the load side of the service disconnecting means", per NEC Sec 250.24(5). Does refer to an exception listed in Sec 250.32, which does not apply, in my opinion, as explained below.

NEC 2005, Section 250.32 is for "Two or More Structures Supplied from a Common Service".

The operative word is supplied. Your first structure is solely for the purpose of housing the generator and transfer switch. And,"No other metallic paths" also means no telephone or CATV cables.

Your friend's electrician is exactly correct. And yes, ranges and dryers now require 4 wire branch circuits, to include an equipment grounding conductor.Perhaps you should be hiring your friend's electrician, seems yours either is not knowledgeable with basic residential services, or is this a fixed price contract and he wants to save costs on his end.

I am not clear if your electrician is running 3 wire or 4 wire from the Main/ATS. I do get he is running 3 wire from the Main/Panel on the exterior of the home. I also get he is running 3 wire from the main service panel downstairs to a subpanel upstairs, this is entirely wrong, no matter what is going on outside.

According to the instruction manual Page 2, Line #3:
MAIN CIRCUIT BREAKER OR MAIN LUG WIRING
3. If required by the local code, install the enclosed green neutral bonding screw through the hole in the neutral bar. Thread the screw into the hole in the enclosure and torque to the value specified on the card shipped with the bonding screw.

This means a separate equipment grounding bar needs to be purchased and bolted directly onto the panel' metal box, and the green screw is not to be installed into/thru the main neutral bar, which would bond the neutral to the box.These can be found on Page 63 of the HomeLine Catalog.

Nothing should ever need a saw. Just reading, and understanding the instructions and the options available is sufficient.

Hope this helps. You should ask your electrician for a discount.

Find attached project layout diagram in PDF form.

I think I am clear regarding the grounding/bonding requirements. My residential electrician and I had a talk yesterday and I explained that this issue must be resolved correctly. He is licensed in Alabama and Georgia. The utility company is Alabama Power Company. He works in several counties in both states, all of which either seem to have different requirements or don't seem to inspect this situation at all, per him. He indicated that he has done it both ways (3-wire or 4-wire), just depending on which county he is in at the time. He doesn't feel that it makes any difference because he says that its all is mute when you bond everything together at the utility company interface (service disconnect). He is open to doing it which ever way I want (I am just the dumb engineer, I am not a master licensed electrician, so I am not comfortable telling him how to do it, just trying to give him some solid advice). He as agreed to remove any 3-wire feeds and replace with 4-wire.

Remember after installation in my county there is absolutely no inspection at all. I will be the final inspector. If my house burns down though due to electrical faults, the fire and insurance companies may inspect and decree that NEC codes were violated so it matters a lot to me!!

He says everything else he is doing is to code and building requirements, i.e. arc faults in bedrooms, GFCI as req'd, smoke detectors per code, etc. He just is confused (and I think somewhat due to the inconsistency in electrical inspectors in the surrounding counties).

Any specifications on the wire types, sizings, etc on the attached diagram would be appreciated. I am having a commercial group install everything up to the disconnect on the residence. They are go for 4-wire all the way. They are discussing the generator today regarding separately derived vs non-separately derived as you had mentioned in prior posts. The ATS is 2-pole with solid neutral and separate solid ground lugs, non-switched neutral. My question is whether with a non-switched neutral is there more likely a case of lightning damage to the genset from utility power surges on their neutral?

Thanks for any help,

Huck

Attached Images

Electrical Layout.pdf (14.1 KB, 946 views)

Seems both Alabama and Georgia both adopted the 2002 edition so far:

Advertisement for A/E
http://www.dca.state.ga.us/developme.../elect2003.pdf

This means that any electrical work done in both states must follow the NEC 2002, plus amendments.

Alabama has licensing and regulations about who can do electrical work:

electrical contractors/2
ALABAMA STATE BOARD OF ELECTRICAL CONTRACTORS

My point is that at least in Al anyone that does electrical work must be licensed, and follow the adopted code. Got limited time here so I will let you research Georgia laws.

I do not believe that you are ultimately responsible for any faulty wiring.
Perhaps a call to your state's building official may be recmmended, and checking with your insurance carrier.

Since the ATS is 2 pole S/N (soild neutral), the genset system will be considered as a Non-Separately Derived System. No worry on the neutral, it is the only conductor that is intentially grounded, once at the transformer by the utility compnay, and again at your service.Lightning gets induced into the live ungrounded conductors.

Since the commercial contractor seems to be knowledgeable on grounding, ask them what is typical and allowed for a subanel feeder, either 3 wire or 4 wire.

Wow, this just should not be this hard.

On the sketch, nice job, but I need to know specifics on what you need to know for details.

I forgot to add one thing that you mentioned a post or two ago regarding others conductors. The local cable/internet/telephone company piggybacked their hard coax and twisted pair cable approx. 1 foot or so above the power companies primary, as they say is customary. This puts the phone/cable pedestal out near the utility companys ground transformer. Intent is to mimic the same path down to the house, i.e. go above the secondary conductor ditch a foot or two in conduit to the house. The phone company's policy is they must ground to the utility company ground at the entry into the house.

Since there is no ground rod or exposed ground at the house, what is your recommended ground point for this cables entering the house?

Does this change anything regarding the common ground point at the service disconnect?

The power company's calculation based on 4-ton heat pump, other parameters are unknown to me, is that if they were supplying the feed all the way to the house they would use 250mcm. What more do you need to calculate voltage drop (utility calls it flicker voltage)?

Obviously 250 costs more than 4/0 and it is difficult to locate if you purchase as quadriplex cable for underground, therefore we would probably purchase a reel of 250mcm AL and cut individual conductors all as 250, except ground. What do you recommend as the ground conductor size if other conductors are 250?

If we could use common mobile home underground feeder cable (4/0-4/0-4/0-2/0 AL) which around here is about $4.50 per foot of quad, this may be less expensive than single conductor costs combined, but if we get "flicker" on the lights, the utility will not be responsible since they recc. The 250mcm. This is why your opinion on v. drop is important. Simply can anyone say that if we go with 4/0 will the lights dim on heavy load starts?

Thanks again

A follow-up on the house wiring. My electrician has per my request installed a 4-wire service entrance cable (SER I think). I took a photo with my phone (not great qual) for your viewing enjoyment. He has added a lug on the leftmost bus and separated the leftmost bus (now with bare ground wire attached) from the neutral bar that bonded horizontally from the leftmost bus -->N lug --> rightmost bus from the factory. The two busses are now isolated from each other but the neutral is still bonded to the enclosure via the green bonding screw on the right.

Check me on this. You had indicated in an earlier post to add a new ground bus w/ lug and to solidly mount it in contact with the enclosure thereby grounding the enclosure. Well the way it is done the neutral is incorrectly bonded to the enclosure but correctly isolated from the ground. The ground bus is not in contact with anything.

It would appear that to have done it correctly the first time with this particular panel the ground lug should have been applied to the rightmost bus (with that bus separated from neutral) and kept the bonding screw in place. This result would have isolated N from G, bonded the enclosure to G and provided a lug for the service cable bare ground wire on the right.

If the photo is not clear, the leftmost bus and lug are now G, and touches nothing else now. The N lug in the middle is bus bar connected to the N bus on the rightmost side, with bonding screw in place, bonding the N to the case.

You opinion on this?

Huck

Attached Images

 

Response to Post #12-

The phone and cable can ground to the panel, they have, or should, have connectors that allow them to connect the ground directly to the outside of an electrical panel. Or a # 6 Green can be run from you equipment ground bar to the phone and CATV demarcation point for them to connect to.

Nice try, to get a ground rod at the house, but nope, nada, zippo. I got an answer for anything you throw at me.

250 MC is the best way to go for the distance you have and the potential load. The utility is concerned about the starting current of the refrigeration compressor, AKA Locked Rotor Amperage(LRA) , which on refrigeration units can be 6-10 times the running load, plus the load of anything else that may be on at the time.

Keep in mind the utility voltage may be a bit low at times at their transformer, they are allowed a certain percent Vd, and if you line is not what they recommend, the Vd of your line will be affected by their voltage, and you will see the "flicker".

Vd is calculated by 2 x length x amps x resistance per 1000 feet of the chosen wire divided by 1000, or 2xLxIxR/1000=VD

The ohms per 1K/FT can be found listed in Table #8 of the NEC. There are other formulas for calculating Vd, but use constant values for Cu and Al, I find the formula I show to be much more accurate.

NEC recommends that Vd should not exceed 3% for a feeder.

Be sure to use wire that is rated for direct burial if you are not using conduit.

I would recommend using 4" PVC Schedule 40 conduit for such a long run. Then you could use XHHW insulation. For the expense of digging a trench this long, you will virtually eliminate any possibility of a damage UG feeder using conduit. And if it does ever need to be replaced, pull out the old and pull in the new.

In any case use #4/0 Al for the equipment grounding conductor, to keep the overall impedance low for grounding.

Response to Post #13

Yes 4 wire cable is called SER.

My opinion is I think your electrician is a doofus.

Sorry, but this is basic code he should know.

Tell him to remove the green screw from the Neutral, and re-install it into the equipment grounding bar. Or use a jumper wire from the EG bar to the metal box of the panel, using an approved wire lug and a machine thread screw intoa threaded hole.

Thanks tk for you extensive help with this really simple project. I am trying to politely and professionally show my builder that he may be trusting someone (his sub electrician) who may need a continuing education course on NEC code. I don't think the inspectors in this area are aware enough themselves sometimes to check these details (hard to believe though), and correct his deficiencies either.

My builder has contacted an alternate electrician who is coming to inspect the service installation. He called him this morning and he repeated everything you have been saying all along. I think you know what he will say this afternoon when he arrives.

I will post to you what the final conclusions are. I hope we all have learned something from this. I know I have as an old engineer, but I'm paying a lot of money for that electrician to get it wrong.

Thanks
Huck

I certainly understand you wanting to be professional.

Just that we are a bit more direct here in the northeast.

Sometimes downright rude and scarcastic, no southern hospitality here.

Yes, please keep us informed.

Alternate electrician arrived today with builder. I explained what we were trying to do and let him examine the main panel. He agreed that the 4-wire config with neutral bonding screw still in place was incorrect (duh) and advised my builder that several areas of the work would not meet code nor inspection. He confirmed my views to the builder on 4-wire requirements after the disconnect outside the house. Advised builder that 3-wire subfeed to upstairs panel would never have been compliant.

We discussed several points of the code that you and I have kicked around regarding bonding/grounding once at the service disconnect then isolated G to N downstream. After looking at the project layout I provided on this forum, he totally agreed (with you) that the system must be 4-wire from the service disconnect at the meter location on.

His answer was correct but his reasoning seems suspect. He says the code indicates that the N-G bonding/grounding should take place at the disconnect before the generator ATS because the ATS is considered an additional circuit?? although non-separately derived. He says each (or any) of the 200A breakers (see prior project layout) could have been claimed as the service disconnect if not for the ATS and bonding/grounding (yes, the ground rod) could be placed at any of the 3 disconnects along the path.

It was my impression from you that the only service disconnect considered valid to bond and ground to was the first one past the meter base regardless of the ATS being there or not. Did I misunderstand you or could you quote the subsection of 250 addressing this. He had his 2002 copy of NEC with him and he looked for his answer but could not exactly find it. I was happy he could produce the NEC, which the initial electrician could not.

He made or implied the following statements in the course of conversation that makes me realize the ambiguity of how the NEC is interpreted:

1) Although not necessary, you are not in violation if you ground the system in more than one physical location (cited commercial work where multiple grounds applied to steel buildings in multiple locations)
2) Indicated to builder that arc-fault breakers may not function correctly if N-G separation (4-wire) is not provided. (Does this mean arc-fault breakers will not work with older 3-wire systems? )
3) Stated main breaker was not necessary inside the house due to disconnect outside. (We had already confirmed that)

In summary he indicated the initial electrician's judgement was in error due to improper grounding and bonding at and after the main panel inside the house.

Our academic question remains to be answered. He is calling his "expert". Guess what, you are mine!! Is it ever allowed to declare any disconnect along the main service feed of a single service the "main disconnect" and ground/bond N-G/ground rod this disconnect? Or is it ever allowed to bond the initial disconnect and then bond another disconnect downstream. I think I know your answer. Please provide backup. This is just a friendly wager with the electrician. My problem is solved, 4-wire all the way.

By the way, the builder is firing the initial electrician tomorrow and hiring the consultiing electrician we met with today to rework and finish the job. He was grateful for my involvement to discover the inadequacies of the initial electrician. I am sorry that all electricians do not keep abreast of current requirements and that I had to become this involved in the job.

Thanks again. Let me know what you think of the information above.

The ATS is not another circuit, the ATS usues no power, it switches between two separate power sources:
because the ATS is considered an additional circuit ???,

I gave the section that applies:
It was my impression from you that the only service disconnect considered valid to bond and ground to was the first one past the meter base regardless of the ATS being there or not. Did I misunderstand you or could you quote the subsection of 250 addressing this. He had his 2002 copy of NEC with him and he looked for his answer but could not exactly find it. I was happy he could produce the NEC, which the initial electrician could not.Grounding the neutral(grounded conductor) shall be done only at the Service Disconnecting means, per NEC Sec 250.24(1).

No connection to ground "shall not be made to any grounded circuit conductor on the load side of the service disconnecting means except as otherwise permitted in this article.", per NEC Sec 250.24(5),

except as otherwise permitted in this article refers to Section250.32, which does not apply to your situation.

Correct:
It was my impression from you that the only service disconnect considered valid to bond and ground to was the first one past the meter base regardless of the ATS

Incorrect, there is only one service disconnecting means for your service, at the meter,
He says each (or any) of the 200A breakers (see prior project layout) could have been claimed as the service disconnect if not for the ATS and bonding/grounding (yes, the ground rod) could be placed at any of the 3 disconnects along the path.

Gee, I wonder why?
He had his 2002 copy of NEC with him and he looked for his answer but could not exactly find it.

Ground rods, and the building steel he is referring to are all called "grounding Electrodes". Yes many buildings may have multiple grounding electrodes, but all connect together and shall only connect to the neutral at one location, at the Main Service Disconnecting Means:
1) Although not necessary, you are not in violation if you ground the system in more than one physical location (cited commercial work where multiple grounds applied to steel buildings in multiple locations)

Incorrect,AFCI do not use nor need an equipemt ground to operate;
2) Indicated to builder that arc-fault breakers may not function correctly if N-G separation
Many new homes use the 4 wire feeder and all new have AFCI breakers as required. Ask him to read the AFCI instructions, see if it states that they do not work on a 4 wire feeder? Now this electrician is starting to make things up.

His reasoning is incorrect, there is the required service disconnecting means at the meter location, no other disconnect is required, but may be if desired.
3) Stated main breaker was not necessary inside the house due to disconnect outside.
Assuming he refers to the one just outside on the house.

Ever? Yes Ever does happen, only with multiple buildings being SUPPLIED by the service in another building, AND ONLY if there is no other continuous metallic path between buildings, such as water lines, telephone lines, CATV, etc, for examples. See Section 250.32

Wow, this road goes on forever. Hope you are not growing too weary of this topic. It certainly seems to be interpreted in many different ways by electricians. I hope keeping the topic in an open forum may clarify the subject somewhat. I thought someone else might jump in by now.

I have pretty much left my own opinions as an engineer out of this, but I might as well jump in. I reviewed the entire section of NFPA 70, NEC 2005, Section 250. I think the confusion comes in the number of different subsections regarding the grounding/bonding topic. I wanted to get this up this morning so I can't cite each article but I can this weekend if needed.

These are my interpretations so far. I am putting them down individually for you to shoot at them directly, but please cite the exact section of code that is your ammunition.

1) All service entrance equipment shall be grounded to a grounding electrode as defined and bonded to the service utility neutral at the nearest point available after the demark, the meter base.

2) It is not clear how many or how they are defined, disconnects are allowed in line with the main service disconnect. The six hand rule does not seem to apply to disconnects not located in a common location or enclosure.

2) It is not defined clearly in a single section that you can OR CAN NOT bond the grounding conductor to a grounding electrode at another point beyond the main service disconnect.

3) Also reference optional standby equipment in section 70.. 2, it think from memory.

Take a good shot at these statements for me. I have a big bullseye on my chest.

Thanks,
Huck

1) All service entrance equipment shall be grounded to a grounding electrode as defined and bonded to the service utility neutral at the nearest point available after the demark, the meter base.

Per 250.24

2) It is not clear how many or how they are defined, disconnects are allowed in line with the main service disconnect. The six hand rule does not seem to apply to disconnects not located in a common location or enclosure.

6 switch rule means that there can be no more than six throws of disconnect switches to shut down an entire service, and all these six switches MUST BE GROUPED at one location to act as one "service disconnecting means", See 230.71. How did the 6 switch rule get here? Not even close to topic.

2) It is not defined clearly in a single section that you can OR CAN NOT bond the grounding conductor to a grounding electrode at another point beyond the main service disconnect.

Have you read and understood 250.24 and 250.32? Seems clear enough to me.

3) Also reference optional standby equipment in section 70.. 2, it think from memory.

Your genset is an Optional Standby System, and a non separately derived system due to two pole ATS, so grounding is per 702.10(B). This is only connection of equipment grounding conductor to the system grounding elecrode conductor. Not the neutral.


I do not know how to make this anymore clear. If anyone can find any reference the pertains to your systrem and finds an applicable section the will allow a N-G connection beyond the main "service disconnecting means", then show me.

Just as the second electrican says, I think it is here, but cannot find it, is because it simply does not exist. Seems someone is trying to interpret the code to suit their needs or opinion.

As I shown before both Alabama and Georgia have reference to NEC, and I am sure there is a person or agency that acts as the Authority having Jurisdiction in each state. Contact that respective person and confirm with them.This should help the difference of opinons and interpretations.