Meter Enclosure Grounding

[erickench]

I decided to start a new thread because I did not want to sidetrack that other thread "Objectionable Current". I just looked at NEC 250.142(B) Exception 2. It state's the following:

It shall be permissible to ground meter enclosures by connection to the grounded circuit conductor on the load side of the service disconnect....

The implication I see here is that Utility owned meters are permitted to be connected on the load side of the service disconnect thus allowing protection from meter socket meltdown. Am I wrong in assuming this?

 

[augie47]

I think the more common occurance is when you have a service disconnect ahead of multiple meters to comply with the "six" disconnect rule (230.71) on multi-meter installations. This exception alows the use of "standard" meter sockets without having to obtain sockets with isolated neutrals.

 

[Pierre C Belarge]

Even though I am not fond of this exception, it is there.

This is not blanket permission to permit the bonding on the loadside, there are restrictions. One being the location of the meter enclosures to the disconnect. I read it that the meter enclosure equipment needs to be immediately adjacent...such as, connected to the disconnect by a fittng, etc...


This provides the installer with some relief in regards to purchasing isolation kits for meter enclosures as long as the installation meets all of the requirements of the exception.

 

[erickench]

Yes but this type of circuit configuration would solve a major problem. The meter enclosure would be protected. Did you see that 'YouTube' video that iwire(Bob) posted on that other thread? That's a real nasty fire!!!

 

[Pierre C Belarge]

Typically, electrical equipment on the loadside of the service disconnect is protected with the equipment grounding conductor, whether that EGC is a conductor or metallic path suitable as an equipment ground conductor.

I am having difficulty trying to decipher what your point is.

 

[erickench]

The circuit breaker in the service disconnect enclosure would protect the meter equipment. Whereas before the meter was connected on the supply side of the CB and did not have any protection as a result. Grounding the neutral in a meter enclosure connected to the supply side of the service disconnect is not gonna accomplish anything. For a circuit breaker to protect something it must be connected upstream from the equipment to be protected.

 

[augie47]

True....but there is always "something" ahead of the service overcurrent --conductors, switching means, etc. I have no statistics (but a lot of history) and I'd say the number of problems where meter sockets would benefit from OCP is minimal (excluding folks tampering)
IMHO

 

[erickench]

Did you see that "YouTube" on the other thread? Not something that you would want to see. Besides alot of problems could be solved by using non-metallic service raceway. If I were the designer this is how I would design my electric service. The meter would be connected on the load side of the disconnect and all raceway on the supply side would be non-metallic. You can't get anything more safer than that.

 

[iwire]

It shall be permissible to ground meter enclosures by connection to the grounded circuit conductor on the load side of the service disconnect....

The implication I see here is that Utility owned meters are permitted to be connected on the load side of the service disconnect thus allowing protection from meter socket meltdown. Am I wrong in assuming this?

You are 100% correct as far as the NEC and the added protection that would be provided to the meter enclosure.

The problem is in many cases the power company will not allow the meter on load side of the service disconnect. Please do not say that the power company 'has no right to do this' as it is a long established practice and one the NEC has no authority to prohibit. 90.2(B)(5)(a)

Here is the video for those that missed it.

http://www.youtube.com/watch?v=yaSPaF7n-OE

 

[erickench]

The meter itself is the property of the utility but it is installed on the customer side of the property line where the utility has no jurisdiction. Property line could be a manhole or a pole. What are their reasons for objecting to this configuration?

 

[iwire]

The meter itself is the property of the utility but it is installed on the customer side of the property line where the utility has no jurisdiction. Property line could be a manhole or a pole.

Did you look at 90.2(B)(5)(a)?

Do you recall that when the customer applies for electrical service they must agree to abide by the utility company's 'terms of service' which typically include language in them that allows the power company control and access to the metering equipment installed on the customers property?

What are their reasons for objecting to this configuration?

Theft of electricity.

 

[iwire]

Here are some of the requirements of one of the local power companies

Check out '705 A'

ARTICLE 700 METERS & GENERAL REQUIREMENTS

701. General
All energy supplied by NSTAR shall, in general, be measured
by appropriate meters for billing purposes. The installation of
meters and metering equipment shall comply with the
requirements set forth in this Article.

Meters will be provided, maintained, installed, moved, and
removed only by authorized NSTAR employees. No changes in
metering equipment of any nature whatsoever are to be
undertaken by any other persons except when special
permission is first obtained from the NSTAR Meter
Operations Department via the NSTAR New Customer
Connect Tech Center. Meter boards, meter banks, sockets,
and protective enclosures, where required, are to be furnished
and installed by the customer or the customer’s electrical contractor.

It is the Customer’s responsibility to assure that all customer owned
equipment is tested and in working order.
For cases where NSTAR is required to operate or install
NSTAR-owned equipment into customer owned equipment,
the customer will be responsible for any repair or
replacement that is necessary due to failure of such customer owned
equipment.

Where, in the judgment of NSTAR, a meter installation may
be subject to damage, the customer will be required to
provide a NSTAR-approved enclosure or other protective
device for the meter equipment or relocate the equipment at
the customer’s expense.

704. Meter Locations
Outdoor meter locations are required for all new, rebuilt,
relocated or extended (residential and commercial)
installations. Exceptions to this requirement will be
permitted only with specific prior approval of
NSTAR. Each location shall be readily accessible to NSTAR
representatives for meter reading, testing, and maintenance.
Service will not be provided if reaching the meter requires

NSTAR employees to use adjacent property, climb fences or
other obstructions, or cause damage to the customer’s
shrubbery or flower beds in gaining access to the meter.
In areas subject to vandalism or damage, permission may be
granted for indoor meters. All such indoor meters shall be in
a readily accessible location next to the service entrance
equipment.

In multiple occupancy buildings, for residential or
commercial use, permission may be granted for
meters to be installed indoors in one common
location accessible to all occupants.

Metering equipment shall not be installed in locations subject
to excessive moisture, dust, heat, chemical fumes or in
locations which are hazardous or inaccessible.

Meter locations are not permitted in living spaces, stairways
or under stairways, display windows, attics, boiler rooms,
elevator shafts; over doors, stoves or sinks; directly under, in
the rear of, or close to, steam, gas, water or drain pipes or
near moving machinery.

In special circumstances, meter locations may be required to
be changed to ensure the integrity of the metering equipment.

A. Outdoor Meters
Outdoor meter sockets should be mounted so that the
face of the meter is less than 6 feet above the final grade.
In no instance will any meter be installed with the center
of the meter more than 6 feet, nor the center of the
meter less than 3 feet above the final grade. A clear area
of 3 feet is required in front of each meter.(See Sketch 13Installation On Poles
NSTAR does not permit the installation of meters on its
poles, except for cable TV amplifiers. Specific approval
shall be obtained by NSTAR for such installations and shall
conform to Massachusetts Electrical Code requirements.
(Refer to Article 907)

Installation On Pedestal
For residential and small commercial applications only, the
installation of the meter socket shall be permitted to be
mounted on a free-standing pedestal pending the approval
of the authority having jurisdiction. The customer may be
required to provide protective devices for and at the freestanding
pedestal. (See Sketch 14)

B. Indoor Meters
Multiple meter bank-installed indoors shall be mounted so
that the center of the top meter(s) is no more than
6 feet and the center of the bottom meter is no less than 3
feet above the floor level. A clear area of 3 feet is required
in front of each meter

705. Location of Service Disconnect and Current
Limiting Protection

A. Hot Sequence
In general, the service disconnect shall be located on the
load side of the meter (hot sequence metering).The
service disconnecting means shall be installed at a readily
accessible location nearest the point of entrance of the
service entrance conductors. (See Sketch 15)

B. Cold Sequence
The service disconnect shall be located on the line side of
the individual meter socket (cold sequence metering) for
the following applications:

1. On all ampere services on 480 volt 3 wire and
277/480 volt 4 wire installations.

2. For all instrument transformer installations, each set of
transformers installed must be cold sequenced and have
its own service disconnect switch except in the case of
padmount metering. (Refer to Article 720)

The disconnect switch in all applications must be in close
proximity and within sight to each meter socket. Contact
NSTAR and the local inspection authority for specific
installation requirements.

http://www.nstaronline.com/business/service_requirements/docs/elecrequire.pdf?unique=20090812164839

The customer has all the right in the world to refuse to agree to any of the above requirements, but they will have to generate their own power as the power company can refuse to supply service to anyone that does not comply with the above rules.

 

[nakulak]

Did you see that "YouTube" on the other thread? Not something that you would want to see. Besides alot of problems could be solved by using non-metallic service raceway. If I were the designer this is how I would design my electric service. The meter would be connected on the load side of the disconnect and all raceway on the supply side would be non-metallic. You can't get anything more safer than that.

I don't see where this provides added safety. In fact, it could be deadly. Not bonding the meter can, CT cabt, or utility cabinets to the service gutters, disconnects, etc. can be deadly if there is a utility side/meter fault to case and a dangerous touch gradient results between cabinets.

 

[iwire]

I don't see where this provides added safety. In fact, it could be deadly. Not bonding the meter can, CT cabt, or utility cabinets to the service gutters, disconnects, etc. can be deadly if there is a utility side/meter fault to case and a dangerous touch gradient results between cabinets.

I believe the added safety he mentions has to do with placing the meter on the load side of the service disconnecting means so there would be over current protection ahead of the meter.

The enclosure would still be bonded.

 

[erickench]

I can understand their concern over theft of electricity. It happens all the time here in NYC. You can cancel your account but the power is still there. I think the law forbids them from taking steps to turn off the power because I already tried asking them.

If the supply side disconnect is open then the meter cannot have a reading. But then again the customer won't get any power either. So how is the electricity stolen?

 

[wwhitney]

If the supply side disconnect is open then the meter cannot have a reading. But then again the customer won't get any power either. So how is the electricity stolen?

I think the point is that if there is a disconnect before the meter, it makes it much safer to tap into the service conductors before the meter, because it can be done without hot work.

Cheers, Wayne

 

[iwire]

I think the point is that if there is a disconnect before the meter, it makes it much safer to tap into the service conductors before the meter, because it can be done without hot work.

That is my understanding as well.

Not that this actually prevents theft but it definitely makes it more difficult.

 

[erickench]

Well the utility commissions should do something about this. Let the utility lock the service disconnects if they want to. But if they're gonna do that then they might as well provide the disconnect as well as the meter. TOUGH BANANA!!! People's safety is at stake.

 

[augie47]

Well the utility commissions should do something about this. Let the utility lock the service disconnects if they want to. But if they're gonna do that then they might as well provide the disconnect as well as the meter. TOUGH BANANA!!! People's safety is at stake.

If you have overcurrent ahead of the meter, as stated it enables the power thief, if they lock the overcurrent device and it "opens", then you have to wait on POCO to unlock it. While waiting your freezer thaws, you want POCO to pay,,,, the overcuurent device ahead of the meter is as likely -or more likely- to "short" as the meter..so we need overcurrent ahead of that ?

 

[iwire]

Well the utility commissions should do something about this. Let the utility lock the service disconnects if they want to. But if they're gonna do that then they might as well provide the disconnect as well as the meter. TOUGH BANANA!!! People's safety is at stake.

I do not entirely disagree with you but I am always against code changes based only on gut feelings without any real substantiation.

Do you know of any injuries caused by the current practices that probably go back 50 to 100 years?