76nemo
Senior Member
- Location
- Ogdensburg, NY
If these switches operate on two wire only with the grounded and grounding bonded at the main, then why are they not required to be GFCI protected???
Parallel path's??
- Thread starter GMc
- Start date
- Status
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
This isn't 'two wire' in the sense of an ungrounded circuit with a hot and neutral but no EGC.
Instead you have a 'switch loop' with a hot coming from the supply, a switched hot returning to the load, and an EGC.
The switch is intentionally passing current from hot to ground in order to provide its operating power. In other words the switch is using the ground as a 'bootleg neutral'.
Arguably this violates the NEC, using the equipment ground conductor as an intentional current carrying conductor.
IMHO the amount of current flowing in this situation is so low as to be acceptable. It is far lower than the permissible inadvertent 'leakage', and lower than the expected capacitive current for any reasonable circuit length. However I feel that the NEC and the UL standards should be brought into agreement.
-Jon
Instead you have a 'switch loop' with a hot coming from the supply, a switched hot returning to the load, and an EGC.
The switch is intentionally passing current from hot to ground in order to provide its operating power. In other words the switch is using the ground as a 'bootleg neutral'.
Arguably this violates the NEC, using the equipment ground conductor as an intentional current carrying conductor.
IMHO the amount of current flowing in this situation is so low as to be acceptable. It is far lower than the permissible inadvertent 'leakage', and lower than the expected capacitive current for any reasonable circuit length. However I feel that the NEC and the UL standards should be brought into agreement.
-Jon
K8MHZ
Senior Member
- Occupation
- Electrician
Reply from Watt Stoppers about sensor switch
Reply from Watt Stoppers about sensor switch
Here is an e-mail and a PDF discussing the issue of current on the grounding conductor in great detail. Since the PDF is lengthy, I will have to put it up in two posts. Also, sorry about the spacing of the PDF, that is a result of cutting from one program and pasting to another. Also, none of the graphics showed up. Anyone wanting a copy of the original PDF can e-mail me at k8mhz@k8mhz.com
First the e-mail:
Hi Mark,
I logged in your forum yesterday to see how I could post my feedback in
response to the comments/concerns about leakage to ground and NEC. Earlier
this year, Watt Stopper released a sales bulletin to educate professionals
on the subject. I tried on your forum to post this document but didn't
find a way to do it. I am hoping you can pass this document to whomever is
interested in hope they will find answers to those questions.
As we indicate in this bulletin, we need all the help we can get to
continue elevate the issue to NEC and ultimately require a neutral in all
wallswitch boxes...
Sincerely,
Eric Fournier
Sr. Product Manager | Commercial Sensors & Controls
Watt Stopper/Legrand
Tel: 760.804.9701 x769
Fax: 760.804. 9712
Email: eric.fournier@wattstopper.com
Visit us at our website: http://www.wattstopper.com
Now, PDF Part 1
Current on ground surprises electricians
and inspectors
No one expects to find current flowing on grounding conductors (except for fault current) but there is
current on the ground in most modern commercial buildings. While there is not a large amount of current,
it is steadily increasing. Recently, electricians, specifiers and building inspectors have begun to recognize
and address this issue because the amount of current is becoming significant, annoying and potentially
hazardous.
Where does the current come from?
A variety of modern electronic equipment and controls are responsible for the current now found on
grounding conductors. Lighting controls, including wall switch occupancy sensors, are some of devices
that ‘leak’ current. They do this because their control circuits must draw small amounts of supervisory
current to power electronic components, and that current needs a return path. The return path could be
through the load (limitations of this option are discussed later), through the grounded conductor (neutral)
or directly to ground on the grounding conductor. To accommodate standard wiring practices, most
commercial wall switch sensors are designed to use the grounding conductor as the return path, resulting
in what is known as grounding current.
Issue: #SB120
Date: January 14, 2008
Topic: Current on ground
Sales Bulletin
GENERAL DISTRIBUTION
Watt Stopper/Legrand • 2800 De La Cruz Blvd., Santa Clara, CA 95050 • Tech Support: 800.879.8585 • www.wattstopper.com
TOP
INDOOR USE ONLY
TOP
INDOOR USE ONLY
System Grounding
Service Hot
Service Neutral
(BLACK) HOT
(GREEN) GROUND
Electrical (WHITE) NEUTRAL
Service
Leak to
Ground
Leak to
Load
(incandescent only)
Leak to
Neutral
CC
EG
CC
EG
(RED) LOAD
(RED) LOAD
(RED) LOAD
TOP
INDOOR USE ONLY
CC
EG
Legend
DC Control
Circuits
Relay
Equipment
Ground
Control Circuit
Return Path
CC
EG
Does this meet code?
The National Electrical Code (NEC) in Article 250 requires the arrangement of the grounding of electrical
systems to be installed in a manner that prevents objectionable currents (250.6). However, objectionable current
is not defined in the NEC. The NEC also states that equipment is acceptable if approved. Approval is at the
discretion of the authority having jurisdiction (AHJ), but suitability for approval is typically based on evidence of
listing or labeling by a qualified testing laboratory, such as Underwriters Laboratories (UL).
There are a number of UL standards that allow current leakage to ground. These standards recognize that
permitting a very low value of current to leak to the grounding conductor is often the only way to ensure proper
operation of certain products. This implies that allowing this low value of leakage current is acceptable practice
and that these products may be installed in accordance with NEC requirements.
The UL standard that covers occupancy sensors, UL773A, allows current up to 0.5mA to leak to ground, and the
majority of UL Listed wall switch sensors put current on the grounding conductor.
Most electrical inspectors and AHJs accept UL Listed products and look to the NEC for guidance about proper
installation and wiring practices. Therefore, in most parts of the country, certain products that leak current to
ground are considered to be code-compliant.
Why fuss over 0.5mA?
The problem is that these small amounts of current add up and can become significant. As energy codes and
green building initiatives dictating the use of controls proliferate, more and more sensors are being installed,
and a potential hazard has begun to emerge.
Several years ago an electrician in Houston who was not aware of the risk sustained a shock from the
grounding conductor and fell off a ladder. This caught the attention of city inspectors who began to investigate
the incident and its causes. As a result, the city of Houston now prohibits controls that use the grounding
conductor as the return path for supervisory current.
In other instances, facilities with controls that leak current to ground have failed Megger tests. The purpose of
a Megger test is to verify the workmanship of the wiring of electrical circuits and measure insulation
resistance. The test is performed by putting DC voltage on building wiring. Test failure occurs because the
circuitry of devices that leak current to ground acts like a high impedance path during the test, so it appears
that there is a wiring fault. Owners of buildings that fail Megger tests are likely to experience delays in
obtaining occupancy permits while the situation is investigated, and may need to replace and rewire controls.
The city of Irvine, in Southern California, prohibited the use of controls that leak current to ground after
becoming aware of this practice following a Megger test.
Engineers at Watt Stopper/Legrand wanted to better understand how multiple sensors could contribute to
these problems, and so they measured the ground current for a single sensor and for 20 sensors connected in
series on a circuit. This quantity represents what might realistically be used to control two three-lamp troffers
in multiple offices, powered from a single branch circuit loaded to approximately 13A. Results are shown
below:
120VAC supply 277VAC supply
Single sensor
Measured current 0.45mA TRMS 0.48mA TRMS
20 sensors
Measured current 9.0mA TRMS 9.5mA TRMS
Watt Stopper/Legrand Sales Bulletin
Issue: #SB120 • Date: January 14, 2008
Watt Stopper/Legrand • 2800 De La Cruz Blvd., Santa Clara, CA 95050 • Tech Support: 800.879.8585 • www.wattstopper.com
Reply from Watt Stoppers about sensor switch
Here is an e-mail and a PDF discussing the issue of current on the grounding conductor in great detail. Since the PDF is lengthy, I will have to put it up in two posts. Also, sorry about the spacing of the PDF, that is a result of cutting from one program and pasting to another. Also, none of the graphics showed up. Anyone wanting a copy of the original PDF can e-mail me at k8mhz@k8mhz.com
First the e-mail:
Hi Mark,
I logged in your forum yesterday to see how I could post my feedback in
response to the comments/concerns about leakage to ground and NEC. Earlier
this year, Watt Stopper released a sales bulletin to educate professionals
on the subject. I tried on your forum to post this document but didn't
find a way to do it. I am hoping you can pass this document to whomever is
interested in hope they will find answers to those questions.
As we indicate in this bulletin, we need all the help we can get to
continue elevate the issue to NEC and ultimately require a neutral in all
wallswitch boxes...
Sincerely,
Eric Fournier
Sr. Product Manager | Commercial Sensors & Controls
Watt Stopper/Legrand
Tel: 760.804.9701 x769
Fax: 760.804. 9712
Email: eric.fournier@wattstopper.com
Visit us at our website: http://www.wattstopper.com
Now, PDF Part 1
Current on ground surprises electricians
and inspectors
No one expects to find current flowing on grounding conductors (except for fault current) but there is
current on the ground in most modern commercial buildings. While there is not a large amount of current,
it is steadily increasing. Recently, electricians, specifiers and building inspectors have begun to recognize
and address this issue because the amount of current is becoming significant, annoying and potentially
hazardous.
Where does the current come from?
A variety of modern electronic equipment and controls are responsible for the current now found on
grounding conductors. Lighting controls, including wall switch occupancy sensors, are some of devices
that ‘leak’ current. They do this because their control circuits must draw small amounts of supervisory
current to power electronic components, and that current needs a return path. The return path could be
through the load (limitations of this option are discussed later), through the grounded conductor (neutral)
or directly to ground on the grounding conductor. To accommodate standard wiring practices, most
commercial wall switch sensors are designed to use the grounding conductor as the return path, resulting
in what is known as grounding current.
Issue: #SB120
Date: January 14, 2008
Topic: Current on ground
Sales Bulletin
GENERAL DISTRIBUTION
Watt Stopper/Legrand • 2800 De La Cruz Blvd., Santa Clara, CA 95050 • Tech Support: 800.879.8585 • www.wattstopper.com
TOP
INDOOR USE ONLY
TOP
INDOOR USE ONLY
System Grounding
Service Hot
Service Neutral
(BLACK) HOT
(GREEN) GROUND
Electrical (WHITE) NEUTRAL
Service
Leak to
Ground
Leak to
Load
(incandescent only)
Leak to
Neutral
CC
EG
CC
EG
(RED) LOAD
(RED) LOAD
(RED) LOAD
TOP
INDOOR USE ONLY
CC
EG
Legend
DC Control
Circuits
Relay
Equipment
Ground
Control Circuit
Return Path
CC
EG
Does this meet code?
The National Electrical Code (NEC) in Article 250 requires the arrangement of the grounding of electrical
systems to be installed in a manner that prevents objectionable currents (250.6). However, objectionable current
is not defined in the NEC. The NEC also states that equipment is acceptable if approved. Approval is at the
discretion of the authority having jurisdiction (AHJ), but suitability for approval is typically based on evidence of
listing or labeling by a qualified testing laboratory, such as Underwriters Laboratories (UL).
There are a number of UL standards that allow current leakage to ground. These standards recognize that
permitting a very low value of current to leak to the grounding conductor is often the only way to ensure proper
operation of certain products. This implies that allowing this low value of leakage current is acceptable practice
and that these products may be installed in accordance with NEC requirements.
The UL standard that covers occupancy sensors, UL773A, allows current up to 0.5mA to leak to ground, and the
majority of UL Listed wall switch sensors put current on the grounding conductor.
Most electrical inspectors and AHJs accept UL Listed products and look to the NEC for guidance about proper
installation and wiring practices. Therefore, in most parts of the country, certain products that leak current to
ground are considered to be code-compliant.
Why fuss over 0.5mA?
The problem is that these small amounts of current add up and can become significant. As energy codes and
green building initiatives dictating the use of controls proliferate, more and more sensors are being installed,
and a potential hazard has begun to emerge.
Several years ago an electrician in Houston who was not aware of the risk sustained a shock from the
grounding conductor and fell off a ladder. This caught the attention of city inspectors who began to investigate
the incident and its causes. As a result, the city of Houston now prohibits controls that use the grounding
conductor as the return path for supervisory current.
In other instances, facilities with controls that leak current to ground have failed Megger tests. The purpose of
a Megger test is to verify the workmanship of the wiring of electrical circuits and measure insulation
resistance. The test is performed by putting DC voltage on building wiring. Test failure occurs because the
circuitry of devices that leak current to ground acts like a high impedance path during the test, so it appears
that there is a wiring fault. Owners of buildings that fail Megger tests are likely to experience delays in
obtaining occupancy permits while the situation is investigated, and may need to replace and rewire controls.
The city of Irvine, in Southern California, prohibited the use of controls that leak current to ground after
becoming aware of this practice following a Megger test.
Engineers at Watt Stopper/Legrand wanted to better understand how multiple sensors could contribute to
these problems, and so they measured the ground current for a single sensor and for 20 sensors connected in
series on a circuit. This quantity represents what might realistically be used to control two three-lamp troffers
in multiple offices, powered from a single branch circuit loaded to approximately 13A. Results are shown
below:
120VAC supply 277VAC supply
Single sensor
Measured current 0.45mA TRMS 0.48mA TRMS
20 sensors
Measured current 9.0mA TRMS 9.5mA TRMS
Watt Stopper/Legrand Sales Bulletin
Issue: #SB120 • Date: January 14, 2008
Watt Stopper/Legrand • 2800 De La Cruz Blvd., Santa Clara, CA 95050 • Tech Support: 800.879.8585 • www.wattstopper.com
Last edited:
K8MHZ
Senior Member
- Occupation
- Electrician
PDF Part 2
Note that at 120VAC 20 sensors put nine milliamps (9.0mA) on ground ? exactly 20 times the single sensor
measurement. This is an excellent illustration of the additive nature of leaking current.
Grounding current can reach levels that pose a risk of electric shock to occupants under conditions of a
compromised grounding conductor in the supply circuit, or maintenance personnel working on a live circuit.
One milliamp will produce a ?startle reaction,? but even this can be dangerous if it causes a fall or causes
contact with a source of higher current. Five milliamps is considered to be the maximum level of ?harmless
current.? Above this level, physiological effects appear. Sustained muscular contraction, and a ?can?t let go?
reaction are noted at 10-20 milliamps, a level approached by the 20-sensor example above.
Grounding current levels between the branch breaker panels and the service entrance, where ground and
neutral are tied together, will be even higher. Grounding current can also lead to tripping of GFCIs or
malfunctioning of other equipment sharing the grounding conductor.
Why is the grounding conductor used as a return path?
Sensor manufacturers could leak the necessary supervisory current through the load for some devices, but
this solution has several drawbacks. Current cannot pass through ballasts and transformers, so this method
limits control to incandescent lamps, which are seldom used in commercial buildings due to requirements of
the same energy codes that dictate sensor use. Leaking to load also requires sizing the device to the load, and
specifying minimum loads to prevent glowing filaments. Finally, having current flowing at the load when the
device is presumed to be off creates a safety hazard.
The best option is to use the grounded conductor (neutral) as the return path. This approach allows control of
all types of lighting loads and creates no safety hazards; it is the best and safest solution. The primary reason
manufacturers don?t use this path is because neutral conductors are not routinely available in wall boxes in
commercial construction. This wiring practice was adopted in the days of old mechanical wall switches, which
had no use for a neutral. While the appropriate code panel has received proposals to update the NEC to
require neutrals in all switch boxes, these proposals have not been accepted.
How can the problem be solved?
After discussion with individuals at UL and NEMA who agree about the potential hazards of grounding current,
Watt Stopper/Legrand has decided to take a leadership position and make the first steps in what the company
hopes will become a trend to address this issue and correct the problem. Watt Stopper/Legrand will offer a
complete line of 3-wire commercial wall box occupancy sensors, using neutral as the return path, and putting
no current on the grounding conductor. The company calls on electrical engineers and other specifiers along
with electrical contractors to specify and install neutral conductors in their projects and avoid the use of
products leaking current to ground wherever possible.
What else can the industry do to help?
A change to the NEC requiring a neutral in all wall switch boxes would lead to the fastest solution to this
problem. If manufacturers could be confident that products using the neutral for the return path would be
purchased without resistance, most would certainly change their designs. Electrical inspectors are key to
achieving code reform. The NFPA code panel must hear from this group in order to reach consensus to change
the standard. Watt Stopper/Legrand urges inspectors to voice their concerns to NEC Code Panel 9.
Without a change to commercial wiring practices, alternative solutions are likely to emerge. However, other
approaches could create hardships for building owners, installers and manufacturers alike.
Watt Stopper/Legrand Sales Bulletin
Issue: #SB120 ? Date: January 14, 2008
Watt Stopper/Legrand ? 2800 De La Cruz Blvd., Santa Clara, CA 95050 ? Tech Support: 800.879.8585 ? www.wattstopper.com
UL has already considered changing its standard to prohibit grounding current because the standard was not
intended to encourage the use of the grounding conductor as a return path. UL?s intention was to allow
unavoidable leakage that is the result of (a) capacitively coupled current to grounded dead metal, (b) the less
than perfect resistance of insulation materials through which the current conducts to grounded dead metal,
and (c) current that conducts across the surface of insulating materials, across a creepage spacing, between a
live part and grounded metal. These are important exceptions and should be retained.
Similarly, the NEC Code Panel has noted that allowable grounding currents should only be those attributable
to component limitations, not currents using the grounding conductor as the designed return path.
If products using ground as a return path are suddenly prohibited, building owners and installers may not be
able to find control solutions for all applications, and manufacturers who have not been proactive in offering
alternatives will be left without saleable products.
What about retrofits?
Unfortunately, in many older buildings it is not feasible to bring a neutral conductor to the switch box, and so
Watt Stopper/Legrand will continue to offer 2-wire commercial sensors in addition to the preferred 3-wire
models. At the same time, the company will work to educate electricians, inspectors and others as to the
potential hazards of such installations so that they take the appropriate precautions to remain safe.
Does this affect residential construction?
Because wiring practices in residential construction differ from commercial construction, Watt
Stopper/Legrand?s full line of residential sensors was designed to use the neutral wire as the return path for
the supervisory current. The company was able to do this because there is a neutral available in most
residential wall boxes. For the few older residences without neutrals, Watt Stopper/Legrand offers a sensor
for incandescent loads only that leaks current to the load.
Because the grounding conductors in most residences are uninsulated, they absolutely must not be used as a
return path. And for this reason, commercial sensors should not be installed in residential applications.
Watt Stopper/Legrand Sales Bulletin
Issue: #SB120 ? Date: January 14, 2008
Watt Stopper/Legrand ? 2800 De La Cruz Blvd., Santa Clara, CA 95050 ? Tech Support: 800.879.8585 ? www.wattstopper.com
Note that at 120VAC 20 sensors put nine milliamps (9.0mA) on ground ? exactly 20 times the single sensor
measurement. This is an excellent illustration of the additive nature of leaking current.
Grounding current can reach levels that pose a risk of electric shock to occupants under conditions of a
compromised grounding conductor in the supply circuit, or maintenance personnel working on a live circuit.
One milliamp will produce a ?startle reaction,? but even this can be dangerous if it causes a fall or causes
contact with a source of higher current. Five milliamps is considered to be the maximum level of ?harmless
current.? Above this level, physiological effects appear. Sustained muscular contraction, and a ?can?t let go?
reaction are noted at 10-20 milliamps, a level approached by the 20-sensor example above.
Grounding current levels between the branch breaker panels and the service entrance, where ground and
neutral are tied together, will be even higher. Grounding current can also lead to tripping of GFCIs or
malfunctioning of other equipment sharing the grounding conductor.
Why is the grounding conductor used as a return path?
Sensor manufacturers could leak the necessary supervisory current through the load for some devices, but
this solution has several drawbacks. Current cannot pass through ballasts and transformers, so this method
limits control to incandescent lamps, which are seldom used in commercial buildings due to requirements of
the same energy codes that dictate sensor use. Leaking to load also requires sizing the device to the load, and
specifying minimum loads to prevent glowing filaments. Finally, having current flowing at the load when the
device is presumed to be off creates a safety hazard.
The best option is to use the grounded conductor (neutral) as the return path. This approach allows control of
all types of lighting loads and creates no safety hazards; it is the best and safest solution. The primary reason
manufacturers don?t use this path is because neutral conductors are not routinely available in wall boxes in
commercial construction. This wiring practice was adopted in the days of old mechanical wall switches, which
had no use for a neutral. While the appropriate code panel has received proposals to update the NEC to
require neutrals in all switch boxes, these proposals have not been accepted.
How can the problem be solved?
After discussion with individuals at UL and NEMA who agree about the potential hazards of grounding current,
Watt Stopper/Legrand has decided to take a leadership position and make the first steps in what the company
hopes will become a trend to address this issue and correct the problem. Watt Stopper/Legrand will offer a
complete line of 3-wire commercial wall box occupancy sensors, using neutral as the return path, and putting
no current on the grounding conductor. The company calls on electrical engineers and other specifiers along
with electrical contractors to specify and install neutral conductors in their projects and avoid the use of
products leaking current to ground wherever possible.
What else can the industry do to help?
A change to the NEC requiring a neutral in all wall switch boxes would lead to the fastest solution to this
problem. If manufacturers could be confident that products using the neutral for the return path would be
purchased without resistance, most would certainly change their designs. Electrical inspectors are key to
achieving code reform. The NFPA code panel must hear from this group in order to reach consensus to change
the standard. Watt Stopper/Legrand urges inspectors to voice their concerns to NEC Code Panel 9.
Without a change to commercial wiring practices, alternative solutions are likely to emerge. However, other
approaches could create hardships for building owners, installers and manufacturers alike.
Watt Stopper/Legrand Sales Bulletin
Issue: #SB120 ? Date: January 14, 2008
Watt Stopper/Legrand ? 2800 De La Cruz Blvd., Santa Clara, CA 95050 ? Tech Support: 800.879.8585 ? www.wattstopper.com
UL has already considered changing its standard to prohibit grounding current because the standard was not
intended to encourage the use of the grounding conductor as a return path. UL?s intention was to allow
unavoidable leakage that is the result of (a) capacitively coupled current to grounded dead metal, (b) the less
than perfect resistance of insulation materials through which the current conducts to grounded dead metal,
and (c) current that conducts across the surface of insulating materials, across a creepage spacing, between a
live part and grounded metal. These are important exceptions and should be retained.
Similarly, the NEC Code Panel has noted that allowable grounding currents should only be those attributable
to component limitations, not currents using the grounding conductor as the designed return path.
If products using ground as a return path are suddenly prohibited, building owners and installers may not be
able to find control solutions for all applications, and manufacturers who have not been proactive in offering
alternatives will be left without saleable products.
What about retrofits?
Unfortunately, in many older buildings it is not feasible to bring a neutral conductor to the switch box, and so
Watt Stopper/Legrand will continue to offer 2-wire commercial sensors in addition to the preferred 3-wire
models. At the same time, the company will work to educate electricians, inspectors and others as to the
potential hazards of such installations so that they take the appropriate precautions to remain safe.
Does this affect residential construction?
Because wiring practices in residential construction differ from commercial construction, Watt
Stopper/Legrand?s full line of residential sensors was designed to use the neutral wire as the return path for
the supervisory current. The company was able to do this because there is a neutral available in most
residential wall boxes. For the few older residences without neutrals, Watt Stopper/Legrand offers a sensor
for incandescent loads only that leaks current to the load.
Because the grounding conductors in most residences are uninsulated, they absolutely must not be used as a
return path. And for this reason, commercial sensors should not be installed in residential applications.
Watt Stopper/Legrand Sales Bulletin
Issue: #SB120 ? Date: January 14, 2008
Watt Stopper/Legrand ? 2800 De La Cruz Blvd., Santa Clara, CA 95050 ? Tech Support: 800.879.8585 ? www.wattstopper.com
crossman
Senior Member
- Location
- Southeast Texas
First, I offer my appreciation to Legrand for providing the info and for being concerned and addressing us here on the forum.
I can see the desire to have a neutral at every switchbox, and it makes sense at certain levels. However, to require extra wire at every switchbox in every house and building all across the country is "out there" in my opinion. Just because some future owner may want some particular product in the future, should that require the waste of tons of copper? And extra expense? And the manufacture of this wasted wire would use up more resources and contribute to the degradation of the environment.
The NEC should not mandate such a thing. If I want a simple single-pole switch, it is ludicrous to force me to add an un-needed neutral to the switch box. The installation with a hot and a switch-leg is safe and that is what the code is (or should be) concerned with.
Now, if some "green" municipality or state wants all energy watt-stopper saver switches whatever, then let them mandate that themselves and require neutrals. The NEC though? NO WAY.
I can see the desire to have a neutral at every switchbox, and it makes sense at certain levels. However, to require extra wire at every switchbox in every house and building all across the country is "out there" in my opinion. Just because some future owner may want some particular product in the future, should that require the waste of tons of copper? And extra expense? And the manufacture of this wasted wire would use up more resources and contribute to the degradation of the environment.
The NEC should not mandate such a thing. If I want a simple single-pole switch, it is ludicrous to force me to add an un-needed neutral to the switch box. The installation with a hot and a switch-leg is safe and that is what the code is (or should be) concerned with.
Now, if some "green" municipality or state wants all energy watt-stopper saver switches whatever, then let them mandate that themselves and require neutrals. The NEC though? NO WAY.
mivey
Senior Member
I agree. Why in the world would we start installing extra "stuff" because of some manufacturer's product requirements when we may not even use these products? Why not just pull some extra wire everywhere just in case we might need it in the future?crossman said:
If the building were designed for those type controls, fine. Making everybody design for those type controls is crazy. Of course, if I were selling these products, it might make perfect sense.
ELA
Senior Member
- Occupation
- Electrical Test Engineer
Thanks for that posting K8mhz. As painful for me to read as it was. Did they say they measured one sensor leakage at 0.48 ma?
I would be concerned if they were using nearly all the 500ua allowed by UL as opposed to the 1 ua or so that we were discussing earlier.
I would be concerned if they were using nearly all the 500ua allowed by UL as opposed to the 1 ua or so that we were discussing earlier.
iaov
Senior Member
- Location
- Rhinelander WI
I agree with Don on this one. The fact that something is not specifcly forbidden does not make it OK.The NEC is very specific as to what the EGC is for.It doesn't need to say it is not to be used as a deliberate CCC.It does not need to say you can't use it to hang cloths on, brush your teeth with, etc.K8MHZ said:
mivey
Senior Member
There would be an exception for this guy:iaov said:
http://forums.mikeholt.com/showpost.php?p=811590&postcount=52
iaov
Senior Member
- Location
- Rhinelander WI
This might be reaching a bit but if you are hooking one side of a device to 277 and the other to the EGC what happens if the device fails. Partialy shorts.Enough impedence to keep the OCP from clearing. You have now energized all things connected to that EGC and have a potential shock/fire hazzard. I agree with the earlier poster who said if he was an inspector he'ld red tag these. I would too.
iaov
Senior Member
- Location
- Rhinelander WI
Thats a funny picture. Looks like some of the "rockers" I worked with last summer in Mo.mivey said:
crossman
Senior Member
- Location
- Southeast Texas
Fifty story office building, 40 switch boxes per floor, average 20 feet of extra #12 white wire per location:
50 x 40 x 25 = 40,000 feet
Maybe that isn't a significant added cost to a job this size, but to me, that is a freaking lot of wire.
Add it up for every new installation in the country, and we are talking huge amounts of wire and money, the majority of which would never be used.
50 x 40 x 25 = 40,000 feet
Maybe that isn't a significant added cost to a job this size, but to me, that is a freaking lot of wire.
Add it up for every new installation in the country, and we are talking huge amounts of wire and money, the majority of which would never be used.
iaov
Senior Member
- Location
- Rhinelander WI
Yep thats a lot of freakin wire. I'm sure the same thing was said when they started requiring EGC's in the first place. Are the benifits of these devices worth all the hassle and exspence? The manufacturer is making the jing off of these things, not the EC's. Manufactures do not care about code or its related issues unless they can squeeze a buck out of it. And if it costs you and me a lot more time and money , so what!
crossman
Senior Member
- Location
- Southeast Texas
But on the other hand, the customer will end up paying for the material and the labor. I suppose if the code required a mega-gold-plated job then there would be more money in the industry to go around. How's that for being totally self-serving?
crossman
Senior Member
- Location
- Southeast Texas
iaov said:
Of course, a lot of times the EGC is/can be an integral part of the wiring method, for instance, EMT, no extra wire needed.
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
There are certainly other methods of solving this problem.
One would be for the NEC to mandate much smaller 'leakage' current than current UL standards. Leakage current cannot be zero, because there will always be _some_ (if only caused by cosmic rays ionizing air!). IMHO a 1uA intentional leaking is not a problem, however I agree that 480uA of intentional leakage is a problem.
Another would be for the NEC to prohibit any _intentional_ use of the EGC as a current carrying conductor. Leakage is still allowed, but not permitted to be designed in.
Such switches and sensors can be powered by means other than a neutral or EGC; the switch drawing 1uA at 277V is using about the same amount of energy as stored in a AAA battery in one year; battery power is an option (but a maintenance nightmare).
I don't believe that this problem is sufficient reason for requiring a neutral at every switch location.
-Jon
One would be for the NEC to mandate much smaller 'leakage' current than current UL standards. Leakage current cannot be zero, because there will always be _some_ (if only caused by cosmic rays ionizing air!). IMHO a 1uA intentional leaking is not a problem, however I agree that 480uA of intentional leakage is a problem.
Another would be for the NEC to prohibit any _intentional_ use of the EGC as a current carrying conductor. Leakage is still allowed, but not permitted to be designed in.
Such switches and sensors can be powered by means other than a neutral or EGC; the switch drawing 1uA at 277V is using about the same amount of energy as stored in a AAA battery in one year; battery power is an option (but a maintenance nightmare).
I don't believe that this problem is sufficient reason for requiring a neutral at every switch location.
-Jon
iaov
Senior Member
- Location
- Rhinelander WI
I like it.crossman said:
- Status