I inspected a house built in 1947 on Monday. This house has a new service drop, new meter, new Service Panel under the meter, and a new 4/0 alum cable to the new Distribution Panel in the garage; all rated for 200 amps. Everything was new to the Distribution Panel but almost all wiring was the original cloth covered cable. There are only two multi-wired circuits, both are the older 3 wire cable; one feeds the oven/stove and the other the clothes dryer. Each has two ungrounded conductors that are correctly wired at the panel but the grounded conductor is attached to the ground bus bar, instead of the neutral bar. Is this correct? Aren’t the grounded conductors to be attached to the neutral bar because they are current carrying conductors? There are no grounds provided to any of the other circuits in this house. Does that make a difference? This panel was approved by the city in 2000. I put in a call to the city electrical inspector to ask about this, but they have not returned my call.
Additionally, someone has switched the dryer receptacle to a four wire receptacle even though the panel is only feeding a three wire cable to the circuit. The clients informed me that they plan to purchase a new clothes dryer before they move in, so I told them they need to have a licensed electrical contractor evaluate the panel, circuit, and receptacle and install the clothes dryer for them to insure safety. Many other electrical issues in this house, enough to keep an electrician busy for a day or two to be sure.
Yes if the panel has separate neutral and grounding busses that are not bonded to each other than those appliance neutrals absolutly need to go to the neutral bus.
Also, new dryers do not come set up with 4 wire cords only. The cord is supplied at delivery to match the house, 3 wire or four. The receptacle needs to remain 3 wire unless a new 4 wire circuit is run.
Brian,
Thanks for the comments.
The city electrical inspector called yesterday, we talked for almost 15 minutes and…believe it or not, they want to see the grounded conductor on the ground bus bar in the sub-panel that I described in my first post. He told me that he’d try and get the NEC information for me. Real nice person, he was very helpful.
I talked with four electricians about this, three have more than 25 years of experience apiece and all but one thought that the grounded conductor should be on the neutral bar in this configuration. The one who hesitated had the most experience and he was leaning toward neutral bar, but was hesitant and said he’d have to check his NEC book before he’d advise one way or the other.
If there are any electrical “heavy-weights” out there who would like to weigh in on this one, I’d appreciate it.
Troy,
I sent you a PM on this…got your e-mail but have to run to the parents and fix the roof…
I should probably post it here as it would be helpful but I have one foot out the door…feel free to post it if you wish…as stated feel free to give me a call if you wish…I accept calls from all NACHI guys if they need it.
Troy,
First of all to be sure we are on the same page, let’s understand that a GROUNDED conductor is a neutral, and a GROUNDING conductor is the bare or green wire used for the safety grounding. They are bonded at the main service into the GROUNDED conductor which continues on to the transformer center tap.
If anyone, inspectors included, tells you to put a GROUNDED (neutral) conductor on a GROUNDING bus in a sub panel they are wrong. GROUNDED conductors carry current and are not allowed on the GROUNDING bus except at the main service entrance, where they become one.
What difference does it make you might ask? Under normal operation, none. But let that grounding path open or become compromised and you now have potential between the grounding path and earth. In other words, the open grounding wire becomes a hot wire between the load and the break.( Any neutral opened after a load will instantly become a hot wire) So you now have an energized grounding path which includes uninsulated conductors, and worse yet, metal pipes, ductwork, and anything else metal that is bonded to the grounding system. (ductwork is bonded to the furnace which is bonded to the gas which is bonded to the water etc).
As an example I will tell you a story about a trouble call I had about two years ago. It was a friend of mine. She told me she had been getting shocks while taking a shower sometimes. I told her I would check it out the following Monday. Well on Sunday morning she called and said there was smoke coming from the gas pipe in her guest house where it went thru the ceiling in the kitchen. I told her to shut off the main and I would be right over.
I immediately rushed over and sure enough, the ceiling was burned black all around the gas pipe. Upon opening the guest house sub panel, I found separate busses for grounded and grounding conductors. However, someone had added two circuits, placing the neutrals on the grounding bus. The grounding path consisted of EMT over the roof to the main, no grounding conductor. Over the years the EMT had begun to separate on the roof, eventually losing continuity. At every joint there were black scorch marks from the EMT carrying this neutral current in it’s degraded state. When the path became so high in resistance, what happened was the neutral current which was on that grounding bus travelled back to the furnace thru the furnace grounding wire which was on the same bus. From there it travelled along on the gas pipe to the water heater, and from there thru the water pipe to the main service grounded conductor (explaining the shower shocks). The gas pipe where it went thru the ceiling was touching against the plaster lath (metal) which must have been in contact elswhere with a grounded object, so current was also travelling thru this metal lath, hence the heating up at this point. Also the entire subpanel was energized since the grounding bus was bonded to it, with the grounded bus being properly isolated. This would have also energized the entire grounding system and anything plugged into it. After moving those two neutrals to the proper bus, the problems all went away. I returned on Monday and pulled in a new feed, since the old feeders were charred at the EMT joints. I also pulled in a grounding conductor!
I hope this explains it in a way that you can see the reason why neutral current is not ever allowed on the grounding path after the first disconnect. It could have caused a fire or an electrocution.
I know this is a long post but if you study it carefully you will understand it clearly, it is really very basic electrical theory.
Brian Winkle, Arizona licensed electrical contractor.
Thats true enough but isn’t the dryer and range 240v thereby making the ground just an equipment bond. The equipment should require 4 wire if required by the manufacturer in the event they need the neutrtal for control circuits.
No, the dryer and range are 240/120 loads. The dryer motor, light and timer are all 120. The range oven light, clock, controls are 120. For many years the neutral was also allowed to be used as the grounding means, but it has always been a neutral, not a grounding conductor. It is still permissable to use the neutral as the grounding means in existing installations, only new circuit installations are required to have 4 wires, except for mobile homes which have required 4 wires forever.
The manufacturer has always provided the 3 wire hookup, L-N-L. The 4 wire hookup is accomplished by using a 4 wire cord and attaching the green wire in the cord to the appliance frame and removing the manufacture’s installed bonding jumper between the neutral and the appliance frame.
Brian,
Thanks for the great posts. I appreciate the information you are providing. As to your earlier question, yes, we are on the same page. The grounded conductor (neutral) is connected to ground. In this case it is pigtailed to a bare ground wire and attached to ground. I will try and post the photo of the panel, but am not sure how to post photos yet. That’ll make our discussion easier.
You stated that it is still permissable to use the neutral as the grounding means in an older installation. That is what the city electrical inspector stated, but he also added that the city would not require a homeowner to run new wires just because they updated the service and panel and the city wants to see that the equipment is grounded.
Again, there are no other ground wires attached to the ground, because there are no ground wires on any of the old two wire circuits. Would that help to make it a safer installation?
Anyway, I’ll try and get you the photo.
Troy,
Did you not get my Private Message I sent through the system…?
Paul,
Yes, thank you, but I didn’t know how to get your post to post so I left it for you to post!
Meanwhile, I’m having fun trying to get my photo of the electrical panel to post, apparently the file size is to large. And my wife is telling me we are late for a dinner party with friends so this may have to wait until tomorrow.
Brian, thanks. Probably help prevent an ouch!#-o
Troy,
I got your e-mail and I have to run over the mountain to my parents and dont have time right now to reply to it other than give you a quick synopsis here, if it does not answer your question please feel free to call me ( 540-607-0116 ).
Basically, they probably did the service change and the grounded conductor to the Range and Dryer was not long enough to make it to the terminal bar so they spliced it which is fine really as long as the SIZE of the pigtail meets the size of the wire from the SE conductors.
The wire you are likely seeing to the Range and Dryer are older SE wire…(2) ungrounded conductors wrapped by the Grounded conductor.
You made a statment about a Sub panel…Is their one in the installation…because if their is only (1) panel after the meter cab then it is a service panel and the grounded and grounding conductors will terminate on the same buss bar…you only separate the two PAST that point to a " remote distribution panel" or as some call it Sub-Panel…
Now are you saying their is a MAIN under the panel and a SUB PANEL at the garage…if that is the case their is an allowance in the NEC that says you only have to run 3 wires to a detached garage IF their is no potential between them ( 250.32(B)(2)…if their is a telephone line between them or a fence or anything that could potentially conduct between them then the 3 wire is not allowed or if their is any GFCI on the common ac system…in all cases a GEC and GE must be at the detached garage in either installation and most CERTAINLY if they intended to use the 250.32(B)(2) ruling.
ON a side note…I have only ONCE seen the 250.32(B)(2) be applied where I was certain no parrallel paths have potential to happen…most of the time something as small as a telephone line from the house makes the 250.32(B)(2) NOT a option…plus it is just not a good method…( note we are talking 2002 NEC here )
If the garage is attached to the house…the local inspector is** WRONG**…it must have a 4 wire setup…now that does not say it is that way…many years ago the NEC may have been LAX on this…I am only 36 so I only observe the CODE in the years I have delt with it…I dont care about what was allowed in 1929…you know what I mean…BUT regardless as a HI I would call out this IF the garage is attached to the house and no 4 wire setup and isolated grounded conductor…if it is a detached garage I would make sure their is a GEC from that SUB panel to a ground rod or something and that it TRULY meets the 250.32(B)(2) 100%…if not…I would call that out…
Remember ALL NACHI members can call me 540-607-0116 anytime they would like to ask a question in person…
Paul, Phone wire is a bit of a strech isn’t it? What if there is a 30’ aluminum light pole next to the garage and it falls someday at just the right angle it maybe a conductor. Where do you draw the line on “potential path”?
It meets the POTENTIAL even at the minimums…the code says any potential parrallel path…lol…dont you LIKE that example…
Actually I got the telephone line potential from the Nelson County, VA Electrical Inspector one day when I asked him his opinion on it…lol
http://www.mikeholt.com/onlinetraining/page_images/1113857961_2.jpg
The equipment grounding (bonding) conductor, if of the wire type, must be sized in accordance with 250.122, based on the rating of the feeder protection device.
CAUTION: To prevent dangerous objectionable current from flowing onto metal parts of the electrical installation, as well as metal piping and structural steel [250.6(A)], a building or structure disconnecting means supplied by a feeder must not have the grounded neutral conductor bonded to the building or structure disconnecting means. Figures 250–85 and 250–86
(2) Grounded Neutral Conductor. When an equipment grounding (bonding) conductor is not run to the building or structure disconnecting means, the building or structure disconnecting means can be bonded to a grounded neutral conductor installed with the feeder conductors. This is only permitted where there’s no continuous metallic path between buildings and structures, and ground-fault protection of equipment isn’t installed on the supply side of the feeder.
Where the grounded neutral feeder conductor serves as the effective ground-fault current path, it must be sized no smaller than the larger of:
(1) The maximum unbalanced neutral load in accordance with 220.61.
(2) The available fault current in
accordance with 250.122.
CAUTION: Using the grounded neutral conductor as the effective ground-fault current path poses potentially dangerous consequences and should only be done after careful consideration. Even if the initial installation doesn’t result in dangerous objectionable current on metal parts, there remains the possibility that a future installation of metal piping or cables between the buildings or structures could create unwanted parallel neutral current paths.
Author’s Comment: The preferred practice (or at least my preferred practice) is to not use the grounded neutral conductor as the effective ground-fault current path, but to install an equipment grounding (bonding) conductor with the feeder conductors to the building or structure in accordance with 250.32(B)(1).(E) Grounding Electrode Conductor. The grounding electrode conductor for a separate building or structure disconnecting means must terminate to the grounding terminal of the disconnecting means and it must be sized in accordance with 250.66, based on the largest ungrounded feeder conductor.
Question: What size grounding electrode conductor is required for a building disconnect that is supplied with 3/0 AWG? Figure 250–87
(a) 4 AWG (b) 3 AWG © 2 AWG (d) 1 AWG
Answer: (a) 4 AWG, Table 250.66
Author’s Comment: Where the grounding electrode conductor is connected to a ground rod, that portion of the conductor that is the sole connection to the ground rod isn’t required to be larger than 6 AWG copper [250.66(A)]. Where the grounding electrode conductor is connected to a concrete-encased electrode, that portion of the conductor that is the sole connection to the concrete-encased electrode isn’t required to be larger than 4 AWG copper [250.66(B)].
Courtesy of Mr. Mike Holt…
Inpected a home where they updated receptacles with newer ones that had a grounding hole, they were installed on circuits that had no ground provided. Question. what would you put on the report, and the buyer wanted to know why this was wrong and is it a safety thing to be conscerned about?
Paul, your pics are great, I am working under someone right now and when we came to the panel, 1 of your pics had that no more than 1 grounding neutrual should be under 1 screw. I inspected this panel and it had double tapping and like 3 neutrals under 1 screw, was told this was normal practices and you see it all the time, need your prof. opinion. thanks
Brian,
It definately is a “safety concern”. The NEC requires that the ground of the receptacle be bonded to Earth. Ther are some exceptions listed below. Read carefully.
I would write it up as “Receptacles at locations____ are not grounded and represent a potential safety hazard. This should be refered to a qualified electrical contractor for further evaluation”
Receptacle Replacement [210-7(d)] Where Grounding Means Exist. Where a grounding means exists in the receptacle enclosure, grounding-type receptacles shall replace nongrounding type receptacles and the receptacles grounding terminals must be grounded in accordance with Section 210-7(c).
GFCI Protection Required. When receptacles are replaced in locations where ground-fault circuit-interrupter protection is now required, the replacement receptacles must be GFCI protected. This includes the replacement of receptacles in bathrooms, garages, outdoors, crawl spaces, unfinished basements, kitchens, wet bar sinks and rooftops, etc.; see Section 210-8 for GFCI requirements.
Where No Ground Exists. Where no grounding means exist in the box, such as old NM cable without a ground, nongrounding-type receptacles can be replaced with:
· A nongrounding type receptacle.
· A GFCI-receptacle or a grounding type receptacle fed downstream from a GFCI-receptacle. These receptacles shall be marked “No Equipment Ground”.
· A grounding-type receptacle protected with a GFCI circuit breaker. These receptacles shall be marked “GFCI Protected” and “No Equipment Ground”.
Note. The GFCI protection will function properly on a 2-wire circuit without an equipment grounding conductor. The equipment grounding conductor serves no purpose in the operation of the GFCI protection device and has
Thanks Micheal, so the only safety hazard here is that they replaced with wrong type of receptacle correct? If they were just standard 2 prong then nothing has to be said about a ground right? don’t want to alarm buyer?
…but you may want to check for reverse polarity. 