Hello,
I am installing electric service to my new cabin. The panel inside the cabin is 100A. My load in the cabin is very small, mainly lighting, a couple small appliances and a 220v 20a window AC. I need an additional 220v 20a circuit for a well pump in the coming weeks.
I recently had the local Co-op out to give me some options at installing grid service. Since there is a pole nearby, we decided to drop a secondary to a meter pole, then I would run underground to the cabin panel. The cabin is in the woods and the pole is in the pasture. At the point where the meter pole is planned, it is about 145 feet to the cabin through the woods.
The Co-op requires me to erect the meter pole and install a meter base and service disconnect just under the meter base. The meter base is grounded at the pole. I plan to run USE rated direct buried Aluminum cable from the pole to the cabin and the appropriate sized copper from the disconnect to the weatherhead where I meet the Co-op.
So, my questions are:
Any recommedation for the brand and type of service disconnect at the meter pole? I understand that I just need a means of disconnect fused at 100A. Not sure if it would be useful to have another breaker (see second question) or convienience outlet there.
I was planning to add the well pump circuit from the cabin’s main panel. But as an option, I could route both the cabin service and the well pump circuit directly from the meter pole’s disconnect right? I assume that I would need a disconnect with more than one breaker then. Any recommendations?
In terms of grounding. Since there is a ground rod installed at the meter pole, will I be required to run 4 wires (H, H, N, G) from the disconnect on the meter pole to the cabin? Or, can I run just 3 wire (H, H, N)? I currently have the panel at the cabin grounded via a ground rod there. Perhaps I need to modify it.
Likewise, in terms of adding the 220 v 20a circuit for a well pump, I was thinking to add additional capacity in the pump house (a small subpanel) to provide future power to a second pump for the purposes of drip irrigation to a future orchard. I am wondering if then taking power off of the meter pole (described above) becomes a better option than breaking out a a 220v 40a breaker in the cabin, since I will soon be running out of capacity! If this is a better option, then should I consider sizing the meterbase, service disconnect and meter pole wires for 200A service, taking 100A to the cabin and 40 A to the pump house directly from the meter pole?
At the pump house, assuming I have a small subpanel, will the grounding be similar to that of the cabin? In this configuraton, are both the cabin and the pump house considered subpanels with the main disconnect at the meter pole?
Thanks for any ideas, thoughts and advise! I hope my description was coherent!
Scott
Replies
Hadn't heard a requirement for a seperate disconnect, other than every panel has a MAIN breaker. I open and close cottages allot, and some of them are a real PITA with subpanels here, add ons there, keep it simple and safe. As your plans are still forming I would go with a 200 amp service now, rather than upgrade later, there is little more cost to doing this now. For the pump house run a line from the panel, to the pump, and end it with a recepitcle (20 amp T-slot). You can plug anything you want into the unused plug, or add additional recepticles. Since this circuit is exterior, and dealing with water I'ld recomend a GFI breaker on that circuit.
Meter base and panel, what ever your hardware sells would be fine ..
Edited 6/25/2008 8:16 am ET by wane
Hi Wane,
Thanks for your insight. Your advice to keep it safe and simple is well taken. I finished building my cabin 6 month ago and took particular care in designing and building the electric system for current and future needs. Pretty simple but plenty of capacity for a cabin of 600 sq feet.
I think that 200A sizing is purdent, you never know where you may expend 5 or 10 years down the road. We are considering an orchard and the extra power for irrigation my come in handy.
Thanks! Scott
No problem with the electric and water in the same trench.I am asusming that you will be using plastic for the water and not metal.If metal that makes a difference in that you want either thing referenced to a common point and if you run 3 wire from the pole to the house then you would need run the well off the house and use 4 wire from the house to the well.If the water is plastic then you can feed the well from either source and the house and the well can be 3 wire.About direct burial vs conduit, it is a cost benifit trade off..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Thanks Bill, Water is PVC for sure. Good to know that it can share the trench. I will consider conduit. Adds some cost but I have a habit of overdoing things anyway! I am a EE by education and experience but not in power systems so your help in wading through NEC is very helpful. Scott
Does this have to be inspected? And if so what version of the code INCLUDING LOCAL AMENDMENTS is being used?
The reason that I ask is that up to the 2008 NEC that for service to a seperate structure from the service entrance structure (the pole in your case) that if there is no other metallic paths between the structures that you can run a 3 wire feeder and bond the neutral to the ground at the other structure. Other metallic pathes would be metal water line telephone and cable that grounded at the first structure (pole in your case).
Otherwise you need to run 4 wires and keep the neutral isolated at the 2nd structure (house in your case).
In either case each structure needs their own ground electrode system (ground rods and/or other electrodes).
One option at the pole is to get a combo meter panel. These are outdoor meter bases with an attached mini-panel. They have a main and 4-8 slots.
Typically main feeder is just feed off the lugs and then you can install breakers for local receptacle and to feed the well.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Hi Bill, Thanks for the reply. it was very helpful. I'll look into the combo panel. This sounds like a good solution.
Does this have to be inspected? And if so what version of the code INCLUDING LOCAL AMENDMENTS is being used?
No inspections necessary. Not sure of the version of the code, but suspect that 2008 is too new, this is a rural Coop.
The reason that I ask is that up to the 2008 NEC that for service to a seperate structure from the service entrance structure (the pole in your case) that if there is no other metallic paths between the structures that you can run a 3 wire feeder and bond the neutral to the ground at the other structure. Other metallic pathes would be metal water line telephone and cable that grounded at the first structure (pole in your case).
There are no other metalic paths between the pole and the cabin. So it seems that 3 wire is okay then. I am planning to run USE 4/0 AL for direct burial from the pole to the cabin. The Co-op recommends putting it in conduit to be safe. Is this now the normal practise versus simply using direct bury rated cable? The area where this line is running is in the woods, no direct traffic or future construction planned.
Thanks again! Scott
Here is what I was talking about.http://cmsapps.sea.siemens.com/controls/speedfax07/07Speedfax_pdfs/07Speedfax_02/02_19-21.pdfDon't be shocked by the prices. They are about 10 times high.http://www.doityourself.com/invt/9776865What you have is a main breaker that feed the bus bars.At the bottom of the bus bars you have lugs so that you can fed the power, after the main, to the house.You also have spaces for other breakers for local loads or feeders.In this case 4 slots or up to 8 circuits if you use tandems.If I understand correctly you are getting an overhead feed to the pole so it makes sense to mount the meter and panel on the pole rather than uses in pedestal mount as reno suggested.BTW, I am not a fan PVC and would suggesting using PE (polyethalene) tubing. It comes in 250 ft rolls and it is commonly used for well feeds.I am also an EE, but like you not in power. Mostly software for embedded microprocessor used for controls.DanH has a similar background..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Is there a PE conduit that is listed for use as electrical / burial conduit?
"Thanks Bill, Water is PVC for sure. Good to know that it can share the trench. "It might not have been clear, but I was talking about PE for the water line.I am not sure, but it might be a high density polyethalene."Is there a PE conduit that is listed for use as electrical / burial conduit?"But there is HDPE conduit designed for burial."ARTICLE 353 High Density Polyethylene Conduit: Type HDPE Conduit
Summary of Changes
ò Added article covering installation, use, and construction of Type HDPE
conduit.
I. General
353.1 Scope
This article covers the use, installation, and construction specifications for high density
polyethylene (HDPE) conduit and associated fittings.
353.2 Definition
High Density Polyethylene (HDPE) Conduit. A nonmetallic raceway of circular cross
section, with associated couplings, connectors, and fittings for the installation of
electrical conductors.
Article 353, new for the 2005 Code, deals only with high density polyethylene conduit,
Type HDPE. The following information is taken from the UL Guide Card (EAZX) in
the 2004 UL General Information Directory (White Book).
Rigid Nonmetallic Underground Conduit, Plastic (EAZX)
One type of conduit under this guide card is High-density Polyethylene Conduit: Type
HDPE Conduit, Schedule 40. High-density polyethylene (HDPE) Schedule 40 conduit
is a plastic type of rigid nonmetallic conduit, for use only when installed underground.
The HDPE Schedule 40 conduit is intended for direct burial with or without being
encased in concrete. The conduit is intended for use in ambient temperatures of 50░C
or less. Unless marked otherwise, HDPE Schedule 40 conduit is intended for use with
wires rated 75░C or less. HDPE Schedule 40 conduit, when directly buried or encased
in concrete, may be used with wires rated 90░C or less. Where conduit emerges from
underground installation, the wiring method shall be of a type recognized for the
purpose. HDPE conduit is designed for joining by threaded couplings, drive-on
couplings, or a butt-fusing process. Instructions supplied by the solvent-type, HDPE
specific, cement manufacturer describe the method of assembly and precautions to be
followed. Samples of High Density Polyethylene Conduit: Type HDPE Conduit, are
shown in Exhibit 353.1."http://www.lamsonpipe.com/HDPE.php.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Thank you .... I had forgot about this new material - introduced last code cycle - and have not seen it as yet.
I forget the name of the company that sells it, but you can get that HPDE stuff with the conductors already installed. It comes on a big reel and gets installed with a vibratory plow. I've seen it used on a few projects, it can save a lot of time over having to install conduit first and then come back to pull the cable later.
I bet it would! Remember, though ... one reason I like BIG pipe is for the option of later adding or replacing wires. For example, our OP will probably be quite happy with #6 copper and a 40 amp supply today .... but if he ever want to increase that to 100 amps he'll need #2 wires, which are somewhat larger.
I bet you have seen a lot of it, just not up closse and personal.Around here I see it (or something similar) all the time being installed along the roads using directional boring. Used for fiber optics.Also I see it the orange version terminating at a telephone pole for cable to the house..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Also I see it the orange version terminating at a telephone pole for cable to the house
Interesting. I've seen orange going in along ROW for fibre installs, if clearly long-haul.
Locally, all cable is hung from poles--buried service is much, much, extra 9which is very annoying since all you really get for the $8-900 installation bill is coax in a poorly-dug (and less well-covered) ditch.
The NG around here is in PE in colors from a yellow to yellow-orange to orange. Always wonder if that relates to how long the reel of tubing sat in the yard <g>>Occupational hazard of my occupation not being around (sorry Bubba)
Hi Bill, Thanks for the box reference. I see on the link you sent that they have this same box in a ringless and ringed style. Can you tell me the difference between ringed and ringless? I googled this and not much came up! Thanks. Scott
I really don't know. It is question like this where my lack of background shows up.I think that it has something to do with how the meter mounts and the local POCO would tell you which type.If you find out lets us know..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Hi Bill,
In talking with the poco, they explained that it has to do with how the meter is held in place or secured. A ringless base uses the front cover to directly secure the meter. A ringed meter base has some sort of ring that attaches around the meter to secure it. I'm still a bit sketchy on the difference having only seen a ringless version! Scott
The ring secures the meter with a lip cast in the glass to a lip on the base.
The ring has a latch like a little hasp. A little wire with a lead seal or new ones use a plastic doohickey that catches a wire clip.
They are a SOB to pick apart by the way.
Joe H
Your PoCo decides which type of meter they like. The "ring" type have rings that go around the base, securing the meter to the mounting flange. The 'ringless instead are held in place by the sheet metal cover, which has a hole punched in it for the meter to pass through.
As Bill said, there are new rules re subpanels. You need to be sure that you and your inspector are reading from the same page there -- he may interpret differently from what Bill said, and the inspector's interpretation is law, for all intents and purposes.
If the cost isn't prohibitive, it would be wise to pull larger than 100 amp service, and it would be wise to add that utility outlet on the pole. Re the pump, you have to weigh the (in)convenience factor of having the disconnect at the pole vs house, the relative length of the wiring (and related voltage drop), etc.
Hi Dan, I think I will take the advise and pull cable and mount equipment for a 200A service. Will take the cost now because I am sure that I will take advantage of it in the coming years. We would like to move out there eventually. Thanks for your insight. Scott
Scott,
Look very carefully at your options right now!
With such a modest load you might be better off using solar panels or some other locally generated electricity. Solar panels can be backed up with a standby generator and the whole system run into load batteries. Connected to an inverter you have your 110 volts so most appliaces will work but you can also run 12 volt lights available at camping stores for some real cost savings. My neighbor does that at his cabin on an island at lake of the woods.. they run their TV's etc. off 12 volt and have relatively few 110 volt appliances.
The solar panel has the batteries charged up enough for three days pretty heavy use and beyond that they run the standby generator for a few hours every few days. What they really like about this is they can have lights on timers etc coming on and off periodically and a radio on a timer for the day so it appears that someone is always there.
Other than bringing gasolene there (he'd bring some anyway for the boat) there is no monthy bill that has to be paid. He was going to use a diesel generator but he decided that would add complications to his life..
Hi Frenchy, My first desire was to stay off-grid and build a well. I like the idea of being self-sufficient. Solar was an option on the table. Wind is not as the wind charts indicated that it would be insufficent to generate power.
As I added a 220v 20a well pump and a 220v 20a window unit, I thought that the tradeoff was a much more expensive solar system that running a 100w lighting load and a couple hunderd watts of appliances for 6 weekend-days a month.
Any resources on the web you found useful in calculating loads and panel/battery capacities? I've got $140 into this so far and have not made any puchase comittments yet. My estimate for the on-grid option is $1725 for materials. Labor is all me.
Thanks for the suggestion. You've given me pause to rethink my decision. Scott
Scott
That's where the standby generator comes in.. Many have the ability to generate 220 20Amps for the occasion when your well is in demand.. personally to minimise the running of the generator I'd set up a tank to meet short term demands rather than fire up the generator every time I wanted a glass of water.. (your well pump will also last a lot longer)
As for the 220 window unit.. I cool my house (5500 sq.ft.) with 2 small 110 volt A/C window units. Right now I don't have all my wiring done so I'm using extension cords to the A/C units.. The small one I can easily run on a 12 guage extension cord (100 feet long) and the larger unit is on a 12 guage extension 30 feet long.
I checked on voltage drop etc. because I wanted to make sure I've got a lot of 10 guage extension cords in case and there was no measurable drop.
The point I'm making is that you may be over kill on the window unit depennding on how efficent you insulated your cabin. You do not want to over kill A/C. Two small units can be much better than a single large unit..
You're looking for a "Pedestal," such as you might see at a camping park. These have the main breaker, as well as a few other breakers and provision for running a line to your cabin. Two makers of pedestals are Unicorn an Milbank. They are available in several styles; the nicer ones are fiberglass and have a built-in light.
You need to run four wires ... and you need an additional ground rod at the cabin. The cabin will have its' own panel as well.
100 amp is pretty much the minimum service size these days. There is no reason, though, that you can't have, say, a 40 amp two pole breaker at the pedestal, and then run #6's to your cabin panel. Copper only, please.
I strongly recommend you run the wires in 2" PVC conduit, along with another 1" conduit for future TV/ phone lines.
I recommend pipe because it need not be buried quite as deep, and you can replace the wires without digging.
I recommend the large sizes for an easier pull, and to allow for larger wire in the future. In both cases, I recommend you use rigid steel 'sweep' elbows at the major turns, and wrap the steel with PVC 'pipe wrap' tape. The friction of pulling wires around corners can cut into the plastic pipe.
The same principles apply to your run to the pump house. Start off with a panel out there. You'll want a light, and a convenience receptacle, whenever you need to work there.
If you really want a 'first class' job, consider filling the ditches 90% with sand. It will sure make digging easier if you ever do need to dig again .... and eliminate the possibility of a rock cutting into the pipe.
No matter the method, I suggest a ditch at least 24" deep. With a sand bed, the pipe will be as close as 18" to the ground. This places it below any irrigation, or a casual shovel bite, and away from the worst roots.
If I may add my 2 cents worth....Around here we would use the USE triplex cable. It has a neutral that is a size or two smaller than the hot wires.
We use a circuit breaker at the pole, not a disconnect. This provides some protection in case somebody digs in to the cable going to the cabin.
Unless there is some unusual risk, we never use conduit. There must be thousands of miles of utility underground wiring around here where the cable is simply buried a few feet underground with no conduit.
I would spend my money digging a deeper trench for the cable.
"We use a circuit breaker at the pole, not a disconnect. "That is a disconnect..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Bill, I mean we use a circuit breaker as a form of circuit protection instead of just using a simple disconnect, which offers no circuit protection.
The typical setup they use around here would have a meter at the pole and a simple disconnect below it.
Some cities here require the circuit breaker instead.
I would have to have to look at the order of the common's in the code.But I suspect that overload device is also required. But it has to be rated for use as a disconnect.And that is what service entrance rated equipment does.Now if service went straight to the house it would need something that functions as both an overload and a disconnect, typically that is a panel with a main disconnect.But if you have a overload (and disconnect) at the pole then you can get by with a just a disconnect at the house. But 99.9999% of the time a panel would be used with main disconnect/overload breaker.All of these comments are about 100 t0 320/400 amp single family residential service.Once you get into the higher current (and/or higher voltage) commcerail and multifamily housing it can be much different in details, but the concept is the same.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
If the main panel is to be the disconnect, does it have to be located in a certain place, like within X feet of an exterior door or something?
"If the main panel is to be the disconnect, does it have to be located in a certain place, like within X feet of an exterior door or something?"No."(1) Readily Accessible Location The service disconnecting means shall be installed at a
readily accessible location either outside of a building or structure or inside nearest the
point of entrance of the service conductors.
(2) Bathrooms Service disconnecting means shall not be installed in bathrooms.""(C) Access to Occupants In a multiple-occupancy building, each occupant shall have
access to the occupant's service disconnecting means."There is also a requirment for working space around a panel with limits the max and min height. But other wise it can be located anyplace..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Thanks. I remember about the "working space" around the panel issue, but our electrician mentioned something about out main panel having to be within something like 6' of the basement door. It is, so there isn't a problem, but that must be a local fire code thing.
Another reason for having a panel with multiple breakers on the pole would be to feed a future shop/barn. If you have an orchard of any size you will be storing/repairing equipment at some point. This maybe something else to discuss with the coop when they size your feed to the pole.
Thanks all for your advise! Last weekend we built and put up the meterpole, wired up both the meter and main panel (attached to the pole). This was the first time with building and setting up a meterpole. A good experience! Your advise has been very appreciated.
I do have a question about grounding at the meterpole. The poco's engineering drawing indicates that I am to ground the meterbase with # 6 to a ground rod adjacent to the pole (which I did). This grounding wire is to be connected within the meterbase so it effectively ties the incoming/outgoing neutral to the ground rod. Out of the meterbase and into the main panel, located immediately under the meterbase, my 3 wires connect into the main breaker and the neutral busbar. From there I will serve a cabin subpanel (100A) and a pumphouse subpanel (40A)
From diagrams and illustrations I have seen on this site and others for main panel installation, they show that a ground wire (in the main panel) is connected from it's neutral bar to this ground rod but it does not show the meterbase itself grounded, as my poco indicated.
So, Given my poco meterbase grounding scheme, does there need to be a ground wire that connects the meterbase (that is currently attached to ground via a rod) to the neutral bar of the main panel? Is there some sort of grounding jumper needed between the 2 boxes? Should there be a bonding screw set to tie the main panel enclosure to the neutral bar (and ground)?
I just assumed that since the neutral wire coming into the main breaker panel is already grounded at one point, what is the need to run a separate ground wire from the meterbase to the main panel. Seems like your setting up a parallel grounding path.
Can someone help my understand the proper grounding paths?
Thanks again!
Scott
Edited 7/1/2008 7:59 am ET by sgoodno
Edited 7/1/2008 8:16 am ET by sgoodno
2 basic rules1. the ground electrode conductor can be bonded to the neutral at any point from the weather head through the meter to the panel.2. All exposed metal parts need to be bonded to the neutral/ground electrode.I am assuming that you did not use the combo meter panels. If you did they are allready all bonded.And if not how are they connected.They can be bonded by metal conduit between them, but there are a number of special requirements, such as the use of special bonding fitings and I am really not up on the details. So wait for some more replies.Or you can just loop the ground electrode conductor throug the bus on the panel and the to the meter.And there should be a bonding screw/strap in the panel to bond the neutral bus to the case..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Edited 7/1/2008 9:42 am by BillHartmann
Thanks Bill,
I did not use an all in one panel. I could not find any large supply house here in Dallas that carried them in stock and could not wait to do special order from them. I used an 8 space panel with a main breaker installed. The main panel is connected to the meterbase with a metal nipple and metal nuts. So electrically they are the same.
I read a bit about these wire that bond metal components in one of my books but didnt quite understand when they needed to be used.
When you say loop the ground, you mean bring a continuous ground wire from the rod through the main panel and finally to the location in the meter base right?
Thanks again, Not sure if I am being overly conservative but am interested in making sure it is safe!
Scott
"When you say loop the ground, you mean bring a continuous ground wire from the rod through the main panel and finally to the location in the meter base right?"Yes.Post another message to me if I don't get back with some more information by tomorrow..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
250.24 Grounding Service-Supplied Alternating-Current Systems
(A) System Grounding Connections A premises wiring system supplied by a grounded
ac service shall have a grounding electrode conductor connected to the grounded service
conductor, at each service, in accordance with 250.24(A)(1) through (A)(5).
(1) General The connection shall be made at any accessible point from the load end of
the service drop or service lateral to and including the terminal or bus to which the
grounded service conductor is connected at the service disconnecting means.(4) Main Bonding Jumper as Wire or Busbar Where the main bonding jumper
specified in 250.28 is a wire or busbar and is installed from the grounded conductor
terminal bar or bus to the equipment grounding terminal bar or bus in the service
equipment, the grounding electrode conductor shall be permitted to be connected to the
equipment grounding terminal, bar, or bus to which the main bonding jumper is
connected.250.92 Services
(A) Bonding of Services The nonûcurrent-carrying metal parts of equipment indicated in
250.92(A)(1), (A)(2), and (A)(3) shall be effectively bonded together.
(1) The service raceways, cable trays, cablebus framework, auxiliary gutters, or
service cable armor or sheath except as permitted in 250.84.
(2) All service enclosures containing service conductors, including meter fittings,
boxes, or the like, interposed in the service raceway or armor.
(3) Any metallic raceway or armor enclosing a grounding electrode conductor as
specified in 250.64(B). Bonding shall apply at each end and to all intervening
raceways, boxes, and enclosures between the service equipment and the
grounding electrode.(B) Method of Bonding at the Service Electrical continuity at service equipment,
service raceways, and service conductor enclosures shall be ensured by one of the
following methods:
(1) Bonding equipment to the grounded service conductor in a manner provided in
250.8
(2) Connections utilizing threaded couplings or threaded bosses on enclosures where
made up wrenchtight
(3) Threadless couplings and connectors where made up tight for metal raceways and
metal-clad cables
(4) Other listed devices, such as bonding-type locknuts, bushings, or bushings with
bonding jumpers
Bonding jumpers meeting the other requirements of this article shall be used around
concentric or eccentric knockouts that are punched or otherwise formed so as to impair
the electrical connection to ground. Standard locknuts or bushings shall not be the sole
means for the bonding required by this section.From the NEC Handbook.Note that method (4) in 250.92(B) requires other similar devices, such as listed
bonding-type locknuts or bushings. Standard locknuts or sealing locknuts are not
acceptable as the ``sole means'' for bonding on the line side of service equipment.
Grounding and bonding bushings for use with rigid or intermediate metal conduit are
provided with means (usually one or more set screws that make positive contact with
the conduit) for reliably bonding the bushing and the conduit on which it is threaded to
the metal equipment enclosure or box.
Grounding bushings used with rigid or intermediate metal conduit or with tubing
(EMT) fittings, such as those shown in Exhibits 250.35 and 250.36, have provisions
for connecting a bonding jumper or have means provided by the manufacturer for use
in mounting a wire connector. This type of bushing may also have means (usually one
or more set screws) to reliably bond the bushing to the conduit. Exhibit 250.37 shows a
bonding-type wedge lug used to connect a conduit to a box..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
I think you are getting overwhelmed by all the info you're getting.
In a situation like yours, the normal method is to ground your circuit breaker panel just as you would if it was in your house.
You would use bonding bushings at both ends of the metal conduit that connects the meter box to the circuit breaker box. A grounding wire would run from the bonding bushing at the meter box to the lug in the meter box
Another grounding wire would run from the bonding bushing in the circuit breaker box to the grounding bar in the circuit breaker box.
You do not want a wire running through the conduit from the meter box to the circuit breaker box
The purpose of the bonding bushings is to make sure that all the metal parts are bonded electrically together. The way you have it (with just the metal lock nuts) holding the conduit into the boxes is not an acceptable way of bonding because of the possible bad connections due to the knockouts where the conduit enters the boxes.
You need to add approved bonding bushings to both ends of the conduit.
Edited 7/2/2008 9:24 pm ET by BoJangles
Thanks! I finally got the boxes wired and grounded properly and the poco came out the next day and ran the secondary to the pole. I'm up and running! well almost...Just now need to connect the main panel on the meter pole to the subpanel in the cabin.
I have a question regarding generator connection at the cabin's subpanel. A bit of a recap first. I have a Main panel with ground and neutral bonded and 2 ground rods at the meter pole. From the main service entry I broke out a 100A breaker to the cabin subpanel. I will run 4 wires to the cabin and at the cabin keep the neutral and ground separate. There is presently a 2nd ground rod at the cabin's subpanel.
Now, I have a generator that I would like to connect at the cabin's subpanel but wanted to understand the ground and interface issues. I thought I wanted a simple DPDT manual trans. switch that will interface with the gen and the feed from the main panel. The gen. is a troybilt and has a bonded neutral and ground. That is, the neutral is connected to the grounding point on the frame.
Q? How do I handle proper connection of the generator to the cabin's subpanel? Does the generator (with its bonded neutral) get connected to the ground rod at the cabin and 4 wires run to the subpanel through a transfer switch. Do I also have to switch the neutral and the 2 hots from the generator? Any suggestions on a simple manual transfer switch? I plan to run the whole subpanel from the generator as there is little load today.
Q? regarding the 4 wire run between the main panel and the cabin subpanel... The wire I was going to order was 1/0 , 1/0, 1/0, 2. Is it the neutral that is downsized to # 2 or the ground wire? In Kingwire's spec sheet it reference a downsized neutral. I'm a little confused as to when and why one of the wires is downsized. I cant seem to find too much here. My loads in the cabin subpanel are mainly outlets and lighting and I have 1 20A DP for a small AC/heatpump.
Thanks as always for your insight. I do appreciate it very much. It's been a pretty good experience over the last year. I built this cabin in the woods, off grid with nothing but dewalt 18v cordless tools. To my surprise they worked out very very well! I could be a poster boy for them! LOL
Scott
No, typically, you don't have to alter the generator wiring. Just make sure you follow their instructions and use an approved "break-transfer-lock" switch.
Your generator has become the isolated main power supply after the transfer switch is thrown and in that case, your cabin panel is not a subpanel anymore.
The neutral conductor in the direct burial triplex cable is often, but not always, downsized just to cut costs and make the cable easier to work with.
Make sure you balance the loads in the cabin so that both hot legs are supplying a similar amount of juice. The load on each hot leg will "cancel each other" and reduce the amount flowing through the neutral and thus you can get by with a neutral that is smaller than the two hot leads.
I see some common items of confusion here ... As you might guess, the goal is to guarantee that you will NEVER have both the PoCo and the genny supplying power to the circuits at the same time. I think the term 'transfer switch' is somewhat misleading. A manual switch is usually, in reality, a bank of six switches. Your circuit wiring - which goes to the panel already - is removed from the breaker that feeds it, is spliced, and run to the appropriate terminal on the transfer switch. On this switch are two other terminals; one goes back to that breaker in the panel, and the other is fed from the generator. There's a breaker or fuse on the generator side of this switch. You'll also, most likely, do the same thing with your neutral wires. Simply put, the electricity will try to 'get home.' That is, electricity from the generator will want to get back to the generator, and PoCo power will want to return to the PoCo. Theory aside, a lot of problems are avoided if your transfer switch also isolates the neutrals of the genny and the panel. This is the step that defines a 'separately derived system.' As for the ground wire ... there is absolutely no problem simply bonding the genny, and the switch(es) to the ground buss in the panel. In most cases, the ground rod for the building is all that you need. Remember this: the ground WIRE is there to make the breaker trip if there's trouble, while the ground ROD is there for lightning protection. One does NOT substitute for the other.