Closed Delta 120/240V 3-phase service

Good grief, Phil! Read! It's not distribution, rather service! The three secondary phases *ARE* on the poles.

Nope, Midwest, Northeast/New England, but I see it everywhere.

>
Reply to
krw
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Try reading Phil. The pigs were already there! Three-phase was already available on the pole; only the drop and meter were needed.

Reply to
krw

Afghanistan?

Illinois, New York, Vermont (haven't looked here in OH).

Sure.

One pig per pole, three wires going between poles, under the MV lines.

City (and state) not big enough to have suburbs.

Reply to
krw

On Thu, 21 Feb 2008 19:50:21 -0500 krw wrote: | In article , phil-news- | snipped-for-privacy@ipal.net says... |> On Wed, 20 Feb 2008 19:37:38 -0500 krw wrote: |> | In article , |> | SW snipped-for-privacy@dsl.pipex.com says... |> |> In article , |> |> charles wrote: |> |> > obviously very different practices on different sides of the pond. |> |> > Virtually all residential distribution over here is 3 phase. The only |> |> > time I've ever spotted single phase is when an isolated property has its |> |> > own transformer. |> |> |> |> I just wish I had three-phase into my house. |> | |> | Different issue. My father wanted three phase into his house in the |> | late '50s. He argued that it was on top of the pole already so it |> | was a simple matter to bring it down to the entrance panel. They |> | told him that they would do it if he guaranteed a $100/month bill |> | (rather steep for the '50s). |> |> There is, afterall, a cost to keep 2 more pole pigs up there. Those things |> are not cheap. | | Try reading Phil. The pigs were already there! Three-phase was | already available on the pole; only the drop and meter were needed.

Try getting a handle on business and economics. The cost of _using_ the equipment has to be paid for. There are costs of maintenance and replacing things that break. If the transformer blows up, the utility replaces it. If it is shared between two businesses, they share the costs. This is not a freebie ... except for the base level of service required for residences.

Reply to
phil-news-nospam

On Thu, 21 Feb 2008 19:50:20 -0500 krw wrote: | In article , phil-news- | snipped-for-privacy@ipal.net says... |> On Wed, 20 Feb 2008 20:18:45 -0500 krw wrote: |> | In article , snipped-for-privacy@cs.ubc.ca says... |> |> krw writes: |> |> |> |> >> In all of the places I've lived, residential areas had |> |> >> single-phase service only: a single MV line running down the top of the |> |> >> poles along the street or alley, and single-phase transformers |> |> >> providing center-tapped 120/240 service to several houses per |> |> >> transformer. |> |> |> |> >Where do you live, Mongolia? The only places I've seen single phase |> |> >distribution is in the middle of the country (rural Vermont, in |> |> >fact). |> |> |> |> Currently, the area around Vancouver BC. Other residential areas with |> |> single-phase service: near Waterloo, Toronto, and St. Catharines |> |> Ontario, near Montreal Quebec. |> |> |> |> Where do you live that has full three-phase MV on top of every pole on |> |> every street in a residential area? And three transformers on every |> |> pole that has a transformer? |> | |> | The transformers aren't on every pole (every third), but the wires |> | are. I see it all over. All you have to do is look. |> |> There are lots of distribution lines with all three phases. There are |> also lots with just one phase. Either way, just one transformer is the |> norm for residential services. | | Good grief, Phil! Read! It's not distribution, rather service! | The three secondary phases *ARE* on the poles. | |> |> >> Given the amount of area covered by single-family houses |> |> >> compared to the area used by commercial/industrial/large residential |> |> >> (high rise), I'd have to guess that more than 50% of the total number |> |> >> of poles that have any transformers carry one single-phase |> |> >> transformer. |> |> |> |> >Your *guess* is wrong. |> |> |> |> Not where I live now, nor where I've lived for decades. Again, where do |> |> you live that has 3-phase on the pole outside every house? |> | |> | Everywhere I've lived (some underground). |> |> You manage to only live in strange places. | | Nope, Midwest, Northeast/New England, but I see it everywhere.

I've lived in some of these areas plus the south. I've never seen any kind of three phase service besides wye (either 208Y/120 or 480Y/277 and in one case 600Y/347) and delta (presumably 240D/120 since there was a center tapped leg on the few I've seen) for three phase and split phase (240/120) for single phase. I've also seen some 2-wire single phase feeding some highway lighting, but I did not know the voltage (could be any of 120, 240,

277, 347, 480, 600 as far as I know).

You're sure none of these are in any abundance where you live?

Reply to
phil-news-nospam

On Thu, 21 Feb 2008 21:39:58 -0500 krw wrote: | In article , snipped-for-privacy@cs.ubc.ca says... |> krw writes: |> |> >> Currently, the area around Vancouver BC. Other residential areas with |> >> single-phase service: near Waterloo, Toronto, and St. Catharines |> >> Ontario, near Montreal Quebec. |> |> >> Where do you live that has full three-phase MV on top of every pole on |> >> every street in a residential area? And three transformers on every |> >> pole that has a transformer? |> |> >The transformers aren't on every pole (every third), but the wires |> >are. I see it all over. All you have to do is look. |> |> I *have* looked where I live. I've told you what I see (a single MV |> wire on the top of the vast majority of poles in residential areas). | | Afghanistan?

If I ever get there, I'll tell you what I see, if I make it back. But I have read some descriptions that would suggest something like 380Y/220 for three phase.

|> The next level up the distribution hierarchy is 3-phase, so 3-phase |> lines do pass through residential areas, but only one phase is tapped |> for the line of poles down each street or alley. |> |> Again, where do you see 3-phase on every pole? | | Illinois, New York, Vermont (haven't looked here in OH).

Maybe you should. You'll find a LOT of 208Y/120, some 480Y/277 (larger buildings), and maybe some leftover 240D/120, as well as single phase service in 240/120. But do take your camera if you are convinced there are some "6 star" services around.

|> Tell us some places. |> Even when there are 3 phases, do the transformers occur in groups of 3? | | Sure.

And how many lugs on each are wired up? Does each transformer have the same number of MV bushings (whether that be 1 each or 2 each)?

|> Or do you mostly get one transformer per pole, tapping only one of the |> 3-phase MV lines? (That's what I see when there does happen to be |> 3-phase distribution). | | One pig per pole, three wires going between poles, under the MV | lines.

That's single phase 240/120 of the Edison split phase variety. No three phase services there.

Look for cases of THREE transformers, each with the same number of MV bushings (either all have 1 or all have 2 each), and at least 3 LV lugs connected on all three. If only 2 lugs are connected on all three, then you have a wye system, usually 208Y/120 but 480Y/277 is possible (600Y/347 is very rare except in Canada). If 2 lugs are connected on 2 transformers and 3 lugs are connected on one transformer, it is probably 240D/120.

Other possibilities also exist. Be sure to get a number of photos at many different angles to get an unambiguous view of exactly how all the wires are connected. If you see one with 3 lugs connected on each of 3 separate transformers, where the middle lugs of each are connected together, and all the outer lugs, plus the joined middle lugs as one wire, supply 7 wires into whatever building is served, then be sure to get a LOT of photos.

Reply to
phil-news-nospam

|>Actually this is quite common. Even if three phase distribution goes |>through a residential area, the transformers on the poles for homes |>along the way are usually just one transformer supplying one phase to |>that bunch of homes. | | Different utilities in different areas have different practices, including | the willingness to bring three phase down a street that doesn't need it | yet, or will never need it.

I can't rule that out. And maybe I've seen it, as I have seen many cases of three phase MV on a residential street without noting whether it was going through to somewhere else or if all three phases were used (such as by three separate single phase taps). A few streets in town here have two sets of three phase MV. I'm guessing some have special uses (like a hospital circuit) or are feeding strictly to further distance circuits.

Reply to
phil-news-nospam

yes, very useful. A few years ago, the phase from which our house was supplied kept tripping out. I seemed to complain more than others, so the house was swapped on to phase 2 (Yellow, White, or whatever).

Reply to
charles

On Fri, 22 Feb 2008 20:49:29 +0000 (GMT) charles wrote: | In article , | Stuart wrote: |> In article , |> charles wrote: |> > obviously very different practices on different sides of the pond. |> > Virtually all residential distribution over here is 3 phase. The only |> > time I've ever spotted single phase is when an isolated property has its |> > own transformer. | |> I just wish I had three-phase into my house. | | yes, very useful. A few years ago, the phase from which our house was | supplied kept tripping out. I seemed to complain more than others, so the | house was swapped on to phase 2 (Yellow, White, or whatever).

And someone else's house got swapped over to the bad phase.

Reply to
phil-news-nospam

Phil, try getting a handle on reading comprehension; They're ALREADY THERE!

Reply to
krw

In a residential neighborhood? Get real!

Reply to
krw

They surely wouldn't be called that because it's a stupid idea.

Never climbed a pole, but all three phases are used for Edison 240V service. How may lugs is that?

Bullshit! The three wires were the three phases. You could see the connections on the pigs.

Exactly!

I'm not in the business of supplying your curiosity.

Reply to
krw

They stopped bothering about that years ago. Just before the problem, a whole group of 24 new bungalows was all put on one phase. And yes it was the one that kept tripping,

Reply to
charles

On Fri, 22 Feb 2008 19:52:27 -0500 krw wrote: | In article , phil-news- | snipped-for-privacy@ipal.net says... |> On Thu, 21 Feb 2008 19:50:21 -0500 krw wrote: |> | In article , phil-news- |> | snipped-for-privacy@ipal.net says... |> |> On Wed, 20 Feb 2008 19:37:38 -0500 krw wrote: |> |> | In article , |> |> | SW snipped-for-privacy@dsl.pipex.com says... |> |> |> In article , |> |> |> charles wrote: |> |> |> > obviously very different practices on different sides of the pond. |> |> |> > Virtually all residential distribution over here is 3 phase. The only |> |> |> > time I've ever spotted single phase is when an isolated property has its |> |> |> > own transformer. |> |> |> |> |> |> I just wish I had three-phase into my house. |> |> | |> |> | Different issue. My father wanted three phase into his house in the |> |> | late '50s. He argued that it was on top of the pole already so it |> |> | was a simple matter to bring it down to the entrance panel. They |> |> | told him that they would do it if he guaranteed a $100/month bill |> |> | (rather steep for the '50s). |> |> |> |> There is, afterall, a cost to keep 2 more pole pigs up there. Those things |> |> are not cheap. |> | |> | Try reading Phil. The pigs were already there! Three-phase was |> | already available on the pole; only the drop and meter were needed. |> |> Try getting a handle on business and economics. The cost of _using_ the |> equipment has to be paid for. There are costs of maintenance and replacing |> things that break. If the transformer blows up, the utility replaces it. |> If it is shared between two businesses, they share the costs. This is not |> a freebie ... except for the base level of service required for residences. | | Phil, try getting a handle on reading comprehension; They're ALREADY | THERE!

I can comprehend what you are saying. But it does not apply to how things like billing and tariffs are done. And the reasons and methods are quite logical and sound. If the three transformers are already there, then one of these conditions exists:

  1. They are already in use to full capacity by another customer and cannot be used. If you want to add three phase service at that location, either another set of transformers must be installed, or the existing ones must be upgraded to higher capacity. Either way, the existing customer does not need to pay more for this extra capacity. But the new customer does pay for it. That payment is both for the install work as well as the monthly costs (payback of purchase, or payment on lease, depending on how the utility got them). That payment usually is integrated into the delivery charges (see your local utility tariffs). To ensure enough payment for what is installed, there is a minimum usage charge to get it.

  1. They are in use at less than full capacity. The utility only charges existing customers for what they originally needed or actually need now depending on tariff requirements, and the minimum usage. The excess capacity the utility has to "eat". They can come along, if they wish, and trade out the big cans for little cans. But that costs money they cannot get paid for, so they have to decide which way to go, and usually it is to do nothing. But if things ever do need to be replaced, such as the transformers are damaged in a pole knock-down, they would have to replace them, and they will use the lowest cost materials they have consistent with the customer needs, tariffs, and NESC. Otherwise a new customer pays their fair share for the usage, for the capacity they need, according to tariffs.

  2. They are unused. The utility could just take them any time they need them for some other service. It's usually easier to take them from stock, so it might be a while (many years) before they recover them. If there is a new customer in the mean time, they might get a pass on part of the install cost. But the maintenance cost will be there in the form of a minimum usage in most cases.
Reply to
phil-news-nospam

On Sat, 23 Feb 2008 05:15:47 +0000 (GMT) charles wrote: | In article , | wrote: |> On Fri, 22 Feb 2008 20:49:29 +0000 (GMT) charles |> wrote: |> | In article , Stuart |> | wrote: |> |> In article , charles |> |> wrote: |> |> > obviously very different practices on different sides of the pond. |> |> > Virtually all residential distribution over here is 3 phase. The |> |> > only time I've ever spotted single phase is when an isolated |> |> > property has its own transformer. |> | |> |> I just wish I had three-phase into my house. |> | |> | yes, very useful. A few years ago, the phase from which our house was |> | supplied kept tripping out. I seemed to complain more than others, so |> | the house was swapped on to phase 2 (Yellow, White, or whatever). | |> And someone else's house got swapped over to the bad phase. | | They stopped bothering about that years ago. Just before the problem, a | whole group of 24 new bungalows was all put on one phase. And yes it was | the one that kept tripping,

There's a phase like that around here, and I'm on it. It's not too bad, but almost always when it goes out, the problem is in this one road up a narrow valley where only a single phase runs, and the MV lines are actually under trees well over twice the height of the poles that span all the way across the road. Tree clearing along this road (and many others like it) is pretty much limited to keeping the trees from getting near the lines. But they simply cannot avoid trees spanning over the lines some 20 or 30 feet above them. Then in high wind or ice loading, branches break off and hit the line, sometimes breaking it. Many of these roads only have one phase. Some others do have three phases.

Reply to
phil-news-nospam

|> I've lived in some of these areas plus the south. I've never seen any kind |> of three phase service besides wye (either 208Y/120 or 480Y/277 and in one |> case 600Y/347) and delta (presumably 240D/120 since there was a center |> tapped leg on the few I've seen) for three phase and split phase (240/120) |> for single phase. I've also seen some 2-wire single phase feeding some |> highway lighting, but I did not know the voltage (could be any of 120, 240, |> 277, 347, 480, 600 as far as I know). |> |> You're sure none of these are in any abundance where you live? | | In a residential neighborhood? Get real!

So do you want to detail which of these systems are available to which classes of customer (residential vs. commercial) in the areas where you see them, and approximately what percentage of all service drops use which?

  1. single phase 2-wire 120 volt only
  2. single phase 3-wire 120/240 volt edison split phase
  3. single phase 3-wire 120/208 volt (2 poles of 208Y/120)
  4. single phase 2-wire 240 volt only
  5. single phase 3-wire 240/480 volt edison split phase
  6. single phase 3-wire 277/480 volt (2 poles of 480Y/277)
  7. single phase 2-wire 277 volt only
  8. single phase 2-wire 347 volt only
  9. single phase 2-wire 480 volt only
  10. single phase 3-wire 347/600 volt (2 poles of 600Y/347)
  11. single phase 2-wire 600 volt only
  12. three phase 4-wire 240 volts closed delta, center tapped at 120 volts
  13. three phase 4-wire 240 volts open delta, center tapped at 120 volts
  14. three phase 3-wire 240 volts closed delta
  15. three phase 3-wire 240 volts open delta
  16. three phase 3-wire 480 volts closed delta
  17. three phase 3-wire 480 volts open delta
  18. three phase 3-wire 600 volts closed delta
  19. three phase 3-wire 600 volts open delta
  20. three phase 4-wire 208/120 volt wye
  21. three phase 4-wire 240/139 volt wye
  22. three phase 4-wire 416/240 volt wye
  23. three phase 4-wire 480/277 volt wye
  24. three phase 4-wire 600/347 volt wye
  25. three phase 4-wire 1000/577 volt wye
  26. three phase 4-wire 120/240 volt Scott-T with 208 volt high leg.
  27. six "phase" 7-wire 240/208/120 volt "6 star"
Reply to
phil-news-nospam

On Fri, 22 Feb 2008 19:56:39 -0500 krw wrote: | In article , snipped-for-privacy@ipal.net | says... |> On Thu, 21 Feb 2008 21:39:58 -0500 krw wrote: |> | In article , snipped-for-privacy@cs.ubc.ca says... |> |> krw writes: |> |> |> |> >> Currently, the area around Vancouver BC. Other residential areas with |> |> >> single-phase service: near Waterloo, Toronto, and St. Catharines |> |> >> Ontario, near Montreal Quebec. |> |> |> |> >> Where do you live that has full three-phase MV on top of every pole on |> |> >> every street in a residential area? And three transformers on every |> |> >> pole that has a transformer? |> |> |> |> >The transformers aren't on every pole (every third), but the wires |> |> >are. I see it all over. All you have to do is look. |> |> |> |> I *have* looked where I live. I've told you what I see (a single MV |> |> wire on the top of the vast majority of poles in residential areas). |> | |> | Afghanistan? |> |> If I ever get there, I'll tell you what I see, if I make it back. But |> I have read some descriptions that would suggest something like 380Y/220 |> for three phase. |> |> |> |> The next level up the distribution hierarchy is 3-phase, so 3-phase |> |> lines do pass through residential areas, but only one phase is tapped |> |> for the line of poles down each street or alley. |> |> |> |> Again, where do you see 3-phase on every pole? |> | |> | Illinois, New York, Vermont (haven't looked here in OH). |> |> Maybe you should. You'll find a LOT of 208Y/120, some 480Y/277 (larger |> buildings), and maybe some leftover 240D/120, as well as single phase |> service in 240/120. But do take your camera if you are convinced there |> are some "6 star" services around. | | They surely wouldn't be called that because it's a stupid idea.

I don't know what they would call it if they provided it. That name is one I made up just to have a way to refer to it until someone picks or reveals a better or already used name. You're the one that says it is already deployed; so you tell me what they call it in your area.

|> |> Tell us some places. |> |> Even when there are 3 phases, do the transformers occur in groups of 3? |> | |> | Sure. |> |> And how many lugs on each are wired up? Does each transformer have the |> same number of MV bushings (whether that be 1 each or 2 each)? | | Never climbed a pole, but all three phases are used for Edison 240V | service. How may lugs is that?

That depends on the exact service. In the typical case there are three transformers forming a closed delta. The primary transformer will have

3 lugs used. This transformer has a 120/240 volt secondary and provides the source of 120 volts. The other 2 transformers are wired to other phases on their primary, and have 2 lugs used at 240 volts. One is wired between one end lug of the first transformer and the high leg. The other is wired from the high leg to the other end lug of the first transformer forming the delta loop. The 2nd 2 transformers are not grounded. They may have (probably do have) an unused center tap lug. A total of 4 wires come off this setup to the service drop in question. These are the three phases plus the neutral from the center tap which is grounded.

Other cases might be 240 volt delta without any Edison, or an Edison service that has no three phase at all.

|> |> Or do you mostly get one transformer per pole, tapping only one of the |> |> 3-phase MV lines? (That's what I see when there does happen to be |> |> 3-phase distribution). |> | |> | One pig per pole, three wires going between poles, under the MV |> | lines. |> |> That's single phase 240/120 of the Edison split phase variety. No three |> phase services there. | | Bullshit! The three wires were the three phases. You could see the | connections on the pigs.

If the service is three phase, they put the three transformers on the SAME pole.

Sure, you could form three phase service by splitting the transformers up on different poles and interconnecting the secondaries between poles. In the extreme case, the middle pole could be getting 120/240 from one phase one an adjacent pole, and 120/240 from the other phase at the other pole, and merge them to have the full "6 star" at the middle pole. But is that actually wired that way for any service drop? The service drop would have 7 (SEVEN) wires if so.

|> Look for cases of THREE transformers, each with the same number of MV |> bushings (either all have 1 or all have 2 each), and at least 3 LV lugs |> connected on all three. If only 2 lugs are connected on all three, then |> you have a wye system, usually 208Y/120 but 480Y/277 is possible (600Y/347 |> is very rare except in Canada). If 2 lugs are connected on 2 transformers |> and 3 lugs are connected on one transformer, it is probably 240D/120. | | Exactly!

But that's not "6 star" at all.

|> Other possibilities also exist. Be sure to get a number of photos at many |> different angles to get an unambiguous view of exactly how all the wires |> are connected. If you see one with 3 lugs connected on each of 3 separate |> transformers, where the middle lugs of each are connected together, and |> all the outer lugs, plus the joined middle lugs as one wire, supply 7 wires |> into whatever building is served, then be sure to get a LOT of photos. | | I'm not in the business of supplying your curiosity.

No, you are in the business of not knowing the difference between differnt kinds of three phase service configurations.

Reply to
phil-news-nospam

The HV lines aren't the concern here. Many "country" single primary HV is common with many xformers off 7620V to supply homes with 240/120V. Although sometimes there may be "banks" of xformers on one pole. This does not constitute 3 phase, just a number of homes off the pole. Three phase 13200V HV also runs through some residential areas with the secondary xformer fed off one 7620 phase. Each xformer has one "bug" as a primary feed. But if, per chance, a large business requires 3 phase, it's there. Basically depends on a number of factors. Who installed the primary, is it municipal, is it conglomerate, and what was their budget? And remember, one xformer may feed a number of homes in some areas.

Reply to
Gary

In SW Florida the typical medium voltage distribution is single phase on each run through the neighborhoods. They split out the 3p primary at the main streets. It is 13.5kv to ground.

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This is the typical transformer feeding 2-3 houses on the 120/240v bus at the bottom.

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When I have seen center tapped delta, it is usually only done with 2 transformers (delta vee)

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I did see 120/240 delta with 3 transformers in the keys but it probably grew into 3. (note the center tapped transformer is bigger than the other 2.)

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Reply to
gfretwell

I have been in the electrical craft since Nineteen Sixty Six and I have see n a lot of different service voltages supplied to buildings. First I am no t an Electrical Engineer although I have always been the go to guy on theor y questions that the trainees and apprentices come up with. So I'll just g o ahead and admit that I don't understand how you could get a six phase out put out of a three phase input. If it is a delta secondary it can only be corner or center of one phase grounded as the code specifically requires th ose as the only place the bonding jumper can be connected. I have worked i n manufacturing plants were the delta was ungrounded but elaborate measures were taken to insure that any ground fault was detected well before a seco nd such fault on a different phase had any chance to occur. You simply can not connect any delta system to ground on two separate phases or you have a dead fault. I have yet to see any supply system that allows me to take ha lf phase loads from more than one phase.

Someone has already pointed out that if you have six secondary windings in a star configuration that they would have to be supplied from six phase dis tribution or two of each of the secondary windings would have same primary winding exciting them and would therefore be functionally parallel with no phase difference or voltage between them.

It would seen to me that either 208/120 wye connected supply or a 240/120 c enter tapped phase delta with the resultant high leg on one phase would do what is needed. Either would give you Three phased power for elevator moto rs, air conditioning chiller or whatever the bigger Three phased load is.

As to actually insisting that individual units have 240 volt, Three phase, I have yet to see a situation were that is actually needed. Any Three phas e heat pump, air conditioner, or other motor load that will run on 240 volt three phase that I have had to install could be re-tapped to run on 208 Th ree phase or the motors were labelled as 240,208 Three phase that would run on either without modification. Even single phase home appliances will ru n on either in most cases. Why then would one need to have actual 240 volt s in single or Three phase all the way to the individual unit. I have neve r actually seen Three phase power run to the individual units of an apartme nt building.

If you actually must have 240 volts to each unit in the original posters sm all apartment building; although no one has explained why that might be tru e; then you will need either a single phase supply or a separate branch or feeder to each unit for the 240 volts. I have seen existing buildings with Fourteen units with single phase supply but I have not seen any new constr uction wired that way in the last several decades.

If the elevator motor or some other relatively large load had to have 240 v olt Three phase then the designer should compare the cost of installation a nd operation of either two separate services to supply different voltages o f Three phase or instal a boost transformer off of the 208 volt Three phase to derive the needed 240 volt Three phase. Keep in mind that most utiliti es charge additional monthly fees for a second service to the same premise even if it is only in the form of a fee for reading a second meter each mon th.

As for the utility insisting on anything, they must supply any service that is in the regulatory tariffs maintained by the state regulatory body. Sin ce the derived system transformers that would produce the 120/240 volts fro m the 480/277 are not part of the distribution network they are beyond the utilities power to control. Like anything else on the load side of the dem arcation point it is the exclusive province of the Authority Having Jurisdi ction (AHJ) over the enforcement of the locally adopted electrical code. T he only exceptions I have encountered in almost Fifty years is with publicl y owned utilities because some of those do the electrical code enforcement.

-- Tom Horne

Reply to
Tom Horne

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