Date   

Re: Can we talk safety for a moment?

Cliff Carrie
 

I was a support specialist on large mainframes in the 1960s and 70s. The DC supply outputs were less than 2 volts, but at over 100A. Rings and watches were a no-no, because if you shorted a power bus with one, the ring could heat or even melt unless the overcurrent crowbar circuit triggered. The hot jewellery could cause a traumatic or an eventual surgical amputation. The SCR crowbar circuits shorted the supply output and blew input breakers, so they were normally good protection. I saw one triggered by a piece of bare AWG 30 wire falling across a bus. The system dropped power, but the wire (which should have vaporized) was barely tarnished. That's FAST protection. I still never wore rings or watches. We often had to troubleshoot with power on.


Regards, Cliff Carrie
________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Glenn Little <glennmaillist@bellsouth.net>
Sent: Monday, February 19, 2018 5:10:05 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Can we talk safety for a moment?

It is not necessarily the contact of the ring with an energized circuit
that will cause trauma.
The recoil from a shock with the ring catching on something that will
possibly forcibly amputate the finger.


Glenn


On 2/19/2018 3:41 PM, Richard R. Pope wrote:
David and et al,
For those of us who will not remove their wedding ring/s you can
thoroughly wrap them in adhesive tape. There must not be any exposed
metal and two layers are better than one. Also we were taught in the
AF that if we had to touch a piece of equipment to use the back of our
hand or at least an open hand. A lot less chance of being grabbed.
GOD Bless and thanks,
rich!

On 2/19/2018 8:20 AM, David Berlind wrote:
Whoever wrote "remove jewelry".... I left that one of my pre-work
list. I'm
adding that. Also, even though my bench has a rubber mat on it, I
really
like the idea of putting rubber on the floor. Right now, I stand (with
rubber soled shoes) when I'm working on a live amp because I don't
want my
ass to help complete a circuit that goes through my wooden chair to the
floor. Does anyone have suggestions on where to acquire a relatively
large
but thin sheet of rubber that I can put down under my bench and chair.

On Mon, Feb 19, 2018 at 7:43 AM, jafinch78 . <jafinch78@gmail.com>
wrote:

On Mon, Feb 19, 2018 at 04:35 am, John Griessen wrote:

I don't remember such a rule in the 2004 elec code
Yeah, I've been grilled with implementing systems and methods to
meet and
exceed U.S. Regulatory CFR, USP/NF, EP, NIST, or whomever dealing with
Standard's and... man... the self regulatory industries like law
enforcement, health care and certain I guess union attorney regulated
agencies rackets can override codes if no one enforces.

My recollection is still National Code to bond meter box to ground. I
even have a wire that was cut by and not re-attached by them, though
something to do with the one Utility Company... Indiana Michigan
Power in
my investigation. Code Inspector said the same thing that is unique to
them if I recall correctly.








--
-----------------------------------------------------------------------
Glenn Little ARRL Technical Specialist QCWA LM 28417
Amateur Callsign: WB4UIV wb4uiv@arrl.net AMSAT LM 2178
QTH: Goose Creek, SC USA (EM92xx) USSVI LM NRA LM SBE ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"


Re: Can we talk safety for a moment?

jafinch78 .
 

On Mon, Feb 19, 2018 at 01:25 pm, Richard R. Pope wrote:


Meter Box/es be ungrounded but the Neutral was bonded on the inside of the
Meter Box.
Same in down state Michigan. Forgot about the section regarding the neutral being bonded with a screw in the service panel. I'm guessing that bonds the neutral in the meter box per the wiring spec. Inspector or the Utility Company didn't explain that as I had them on the phone more than once to make sure. For some reason I'm visualizing conduit running between the breaker box and meter box is the same as a ground wire being need... though guessing code notes since the earth ground is bonded at the service panel with neutral bonded at the service panel that is what is required. I'll have to look. I think I need to draw out, read or watch an example of the range of scenarios to visualize the logic since still seem not crystal clear. One ground rod was only required per code so was in spec, though I added a second relating to the 16' distance of the ground rod sphere of influence I think was the term. I'm going off memory. Gas line seemed strange to me to have a ground wire going to the service panel bonded.

Seems to me needs to Mu-Metal, MetGlas or something like 99.5% pure Iron annealed with Hydrogen since the RF looks insane... especially the magnetic field.

Actually, I was thinking to modify the TDS-520 experimentally to run off pure DC battery power to clean up noise and see how that effected performance.

I want to comprehend more the impedance logic for the copper work surface grounded also. As I'm planning on constructing a Faraday Cage and before Dad died... he mentioned I should bury a intermodule shipping container wrapped in concrete footed well of course and meeting code plus extra thickness with other sheilding like lead or ferro-carbon materials added in the mix at least the outer layer well below the frost line. Some installations sounded like they'd metal line the outside actually and have dampening systems around as I was thinking active noise cancelling attenuators on springs might be a novel design. Figure I'd have to do some mesh and exotic baffling for the air exchange and run the system of battery's... most likely wind and solar with disconnects when not charging or opto-couplers. No need for sewage since technically would be a "root cellar" "farm building" "radio shack" Anechoic chamber faraday cage. Not in budget though yet.
.


Re: 7633 after recap

n4buq
 

Never mind. Since the text is oriented properly, that's probably a dumb guess. Sorry.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "n4buq" <n4buq@knology.net>
To: TekScopes@groups.io
Sent: Monday, February 19, 2018 4:47:35 PM
Subject: Re: [TekScopes] 7633 after recap

Does the vertical adjustment move the trace horizontally? If so, then are
you sure you reconnected the pins back to the CRT correctly?

Just a guess...

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "lop pol via Groups.Io" <the_infinite_penguin=yahoo.com@groups.io>
To: TekScopes@groups.io
Sent: Monday, February 19, 2018 4:20:44 PM
Subject: [TekScopes] 7633 after recap

When I got this i was not sweeping or anything I did a recap which was
brutal. Now it sweeps but its sweeping vertically with no trigger.
https://ibb.co/mXW6D7 weird






Re: 7633 after recap

n4buq
 

Does the vertical adjustment move the trace horizontally? If so, then are you sure you reconnected the pins back to the CRT correctly?

Just a guess...

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "lop pol via Groups.Io" <the_infinite_penguin=yahoo.com@groups.io>
To: TekScopes@groups.io
Sent: Monday, February 19, 2018 4:20:44 PM
Subject: [TekScopes] 7633 after recap

When I got this i was not sweeping or anything I did a recap which was
brutal. Now it sweeps but its sweeping vertically with no trigger.
https://ibb.co/mXW6D7 weird




7633 after recap

Brendan
 

When I got this i was not sweeping or anything I did a recap which was brutal. Now it sweeps but its sweeping vertically with no trigger. https://ibb.co/mXW6D7 weird


Re: Can we talk safety for a moment?

Glenn Little
 

It is not necessarily the contact of the ring with an energized circuit that will cause trauma.
The recoil from a shock with the ring catching on something that will possibly forcibly amputate the finger.


Glenn

On 2/19/2018 3:41 PM, Richard R. Pope wrote:
David and et al,
    For those of us who will not remove their wedding ring/s you can thoroughly wrap them in adhesive tape. There must not be any exposed metal and two layers are better than one. Also we were taught in the AF that if we had to touch a piece of equipment to use the back of our hand or at least an open hand. A lot less chance of being grabbed.
GOD Bless and thanks,
rich!

On 2/19/2018 8:20 AM, David Berlind wrote:
Whoever wrote "remove jewelry".... I left that one of my pre-work list. I'm
adding that.  Also, even though my bench has a rubber mat on it, I really
like the idea of putting rubber on the floor. Right now, I stand (with
rubber soled shoes) when I'm working on a live amp because I don't want my
ass to help complete a circuit that goes through my wooden chair to the
floor. Does anyone have suggestions on where to acquire a relatively large
but thin sheet of  rubber that I can put down under my bench and chair.

On Mon, Feb 19, 2018 at 7:43 AM, jafinch78 . <jafinch78@gmail.com> wrote:

On Mon, Feb 19, 2018 at 04:35 am, John Griessen wrote:

I don't remember such a rule in the 2004 elec code
Yeah, I've been grilled with implementing systems and methods to meet and
exceed U.S. Regulatory CFR, USP/NF, EP, NIST, or whomever dealing with
Standard's and... man... the self regulatory industries like law
enforcement, health care and certain I guess union attorney regulated
agencies rackets can override codes if no one enforces.

My recollection is still National Code to bond meter box to ground.  I
even have a wire that was cut by and not re-attached by them, though
something to do with the one Utility Company... Indiana Michigan Power in
my investigation.  Code Inspector said the same thing that is unique to
them if I recall correctly.







--
-----------------------------------------------------------------------
Glenn Little ARRL Technical Specialist QCWA LM 28417
Amateur Callsign: WB4UIV wb4uiv@arrl.net AMSAT LM 2178
QTH: Goose Creek, SC USA (EM92xx) USSVI LM NRA LM SBE ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"


Re: Can we talk safety for a moment?

Richard R. Pope
 

Chuck and et al,
I have just learned something new! It has been a good day. You stated that this is a new requirement. The last house that I wired was almost 15 years ago. UFER wasn't required. Only ground rods were required. My power company here and in the UP required the Meter Box/es be ungrounded but the Neutral was bonded on the inside of the Meter Box. I installed two ground rods for the house in the UP and these were bonded to the Service Panel. I used 4 ground rods for the house in WI and they were also bonded at the Service Panel. I also wired all of the Lighting and GP outlet Circuits with 12Ga Romex, 20 Amp Breakers, and the 20 Amp Outlets for the GP Circuits.
GOD Bless and Thanks,
rich!

On 2/19/2018 2:48 PM, Chuck Harris wrote:
Thank you William. I see I need some corrections in the finer
details of my recollections... It has been 20 years since I let
my license lapse.

In my local code, nothing but the UFER is acceptable anymore
since about 1995. Small commercial buildings can still use a
grounding rod, but residential buildings are all UFER.. The
footing that contains the UFER has to be at least 10 feet in
length, 2 feet wide, and 24 inches under the surface of the
ground. The copper wire can be looped in the footing, as long
as it is more than 12 inches apart, and 6 inches from the
surface of the concrete at any point. It is probably 4 gauge,
but 6 came to mind for some reason... CRS no doubt.

Some localities have such poor soil for grounding that nothing
short of a full ground plane under the building will do. Arizona
comes to mind.

My house has no concrete footer. It uses prefab concrete walls
that are preinsulated, and set on 6 inches of tamped #8 crushed
stone. I complained about the UFER grounding requirement to
the county engineer, and he said he had zero latitude in making
substitutions for the requirement. The reason he gave for the
new (then) requirement was a combination of NEC, and the trouble
that they have had with bad connections and damaged grounding
wires with the ground rod method. I had to pour a special
2 foot by 10 foot footing just for the UFER ground.

Water pipe grounds are frowned upon because it is standard utility
practice today to use plastic tubing from the house to the meter
head.... In the house too, with CPVC. Using gas pipe as a
ground is just stupid. But I have seen it done.

Otherwise, I think what I said is true.

-Chuck Harris

William Ray wrote:
This is supposed to be a discussion about Tek scopes, and I don't mean to be rude, but safety is kind of important, and so its good to be correct about what's acceptable/unacceptable for wiring practices:

It is quite clear from the 2017 NEC, that water pipes, ground-rods, etc. are still permissible in the USA. I'm not sure if gas pipes ever have been.

"Ufer" grounds require considerably more than 8-feet of conductor in the concrete. 6 AWG is not adequate for a Ufer.
...



Re: Tek 465B Preset Potentiometer Problems

Ed Breya
 

Pots and switches in old equipment often have contact problems, but you don't necessarily have to replace them. First try working them over by turning the wiper through the entire mechanical range - a lot of times back and forth, perhaps dozens to a hundred times. Then see if they can be set properly. If not, then replacement is needed. This action helps to cut through insulating films that may form over time, restoring operation.

Same with switches - work them through all their positions/states lots of times, and watch for improvement in action. Sometimes contact cleaners/lubes will help, depending on type.

BTW to avoid damaging trimmer pots especially, use a screwdriver tip that fits the slot well, and avoid over-torquing at the ends, so the (usually plastic) features don't get chewed up.

Ed


Tek 465B Preset Potentiometer Problems

Shailendra Krishan
 

Hello Group,

I have this Tek 465B which was stored away for 5-6 years, and brought out again recently for routine use. As I switched this on, I noticed a few problems.

1. No output on calibrator loop
2. Horizontal trace shrunk to about 7 divisions, not filling the full screen
3. Unstable trace when in channel 1 mode, jumping up and down vertically by about one full division at random
4. Difficulty in getting a stable trigger, could be due to the above mentioned problem in channel 1

I started to troubleshoot the simpler problems first, 1 and 2.

Problem 1 located to R4274, Horizontal X1 gain potentiometer (1K Ohm). This pot was found to be open on the slider terminal, hence acting as a 1K fixed resistor. Replaced this pot and done X1 gain adjustment. Problem fixed.

Problem 2 located to R4293, Amplitude calibration potentiometer (50 Ohm). This pot too had EXACTLY the same problem and was found to be open at the slider terminal. Pot replaced, and the problem fixed. Amplitude calibration done.

Both the pots are Bourns 3352 open cermet type. The question is, whether this is a known problem with Bourns 3352 pots when used in Tek 46x scopes?
Is it probable that there are more such pots in the machine, which are causing the channel 1 problem mentioned above?

I am new to fixing scopes, hence thought of asking the group for inputs.

I am yet to start work on problem 3 and 4, and if I can get group inputs about pot problems, it might help to speed up the work.

Thanks

Shailendra


Tek 2465a grid bias and brightness problems

Francesco
 

Hi, I have recently managed to acquire a 2645a, it is in wonderful
conditions with the nvram battery still ticking since 1986. I have already
performed some maintenance work, replaced all the electrolythic caps on the
A2 and A3 boards, replaced the battery with a tadiran sl-850/p, however I
can't find the cause of the only problem the scope has. The traces are very
bright and even with the intensity control at lowest level they are still
visible, I checked grid bias adjustment but it's already at minimum. All
the intensity controls work fine but the lowest level is too bright. I
checked various test points: power supplies are fine with minimum ripple,
DAC reference voltages on A5 board are also spot on, I checked every
component in the grid bias part of the HV board and they test good. Readout
intensity works fine.
I hope in a suggestion here, I don't want to give up, it's a very nice unit
and it will be a shame to leave it like that.
Thanks in advance
Cheers
Francesco


Re: Can we talk safety for a moment?

John Parkins G8KVP
 

Hello All,

Many, many years ago the BBC were setting up their second TV
channel....... I said it was many years ago! During the testing they
sent out various bits of film and old training information. One I
remember to this day. It was a film about HV circuits and the
practises you should use to be safe.

S.I.D.E was very forcefully put across.

Switch off
Isolate
Dump
Earth

All very much common sense, but it's the process I've always followed
when working on anything with something deadly lurking inside.

--
Best regards,
John mailto:john@g8kvp.com


Looking for late Tek 2232 Svc Manual (070-8548-00)

rclark@...
 

Dear Group- I would like to attempt a recap of the power supply on my B03xxxx Tektronix 2232. Anyone have any tips? I see that the commonly found manuals stop at B029999. Although there is some commonality, the higher voltage sections seem to have changed. I have searched the forum and see that some members may have access to a copy. Thank you


Re: Can we talk safety for a moment?

Chuck Harris
 

Thank you William. I see I need some corrections in the finer
details of my recollections... It has been 20 years since I let
my license lapse.

In my local code, nothing but the UFER is acceptable anymore
since about 1995. Small commercial buildings can still use a
grounding rod, but residential buildings are all UFER.. The
footing that contains the UFER has to be at least 10 feet in
length, 2 feet wide, and 24 inches under the surface of the
ground. The copper wire can be looped in the footing, as long
as it is more than 12 inches apart, and 6 inches from the
surface of the concrete at any point. It is probably 4 gauge,
but 6 came to mind for some reason... CRS no doubt.

Some localities have such poor soil for grounding that nothing
short of a full ground plane under the building will do. Arizona
comes to mind.

My house has no concrete footer. It uses prefab concrete walls
that are preinsulated, and set on 6 inches of tamped #8 crushed
stone. I complained about the UFER grounding requirement to
the county engineer, and he said he had zero latitude in making
substitutions for the requirement. The reason he gave for the
new (then) requirement was a combination of NEC, and the trouble
that they have had with bad connections and damaged grounding
wires with the ground rod method. I had to pour a special
2 foot by 10 foot footing just for the UFER ground.

Water pipe grounds are frowned upon because it is standard utility
practice today to use plastic tubing from the house to the meter
head.... In the house too, with CPVC. Using gas pipe as a
ground is just stupid. But I have seen it done.

Otherwise, I think what I said is true.

-Chuck Harris

William Ray wrote:
This is supposed to be a discussion about Tek scopes, and I don't mean to be rude, but safety is kind of important, and so its good to be correct about what's acceptable/unacceptable for wiring practices:

It is quite clear from the 2017 NEC, that water pipes, ground-rods, etc. are still permissible in the USA. I'm not sure if gas pipes ever have been.

"Ufer" grounds require considerably more than 8-feet of conductor in the concrete. 6 AWG is not adequate for a Ufer.
...


Re: Can we talk safety for a moment?

Richard R. Pope
 

David and et al,
For those of us who will not remove their wedding ring/s you can thoroughly wrap them in adhesive tape. There must not be any exposed metal and two layers are better than one. Also we were taught in the AF that if we had to touch a piece of equipment to use the back of our hand or at least an open hand. A lot less chance of being grabbed.
GOD Bless and thanks,
rich!

On 2/19/2018 8:20 AM, David Berlind wrote:
Whoever wrote "remove jewelry".... I left that one of my pre-work list. I'm
adding that. Also, even though my bench has a rubber mat on it, I really
like the idea of putting rubber on the floor. Right now, I stand (with
rubber soled shoes) when I'm working on a live amp because I don't want my
ass to help complete a circuit that goes through my wooden chair to the
floor. Does anyone have suggestions on where to acquire a relatively large
but thin sheet of rubber that I can put down under my bench and chair.

On Mon, Feb 19, 2018 at 7:43 AM, jafinch78 . <jafinch78@gmail.com> wrote:

On Mon, Feb 19, 2018 at 04:35 am, John Griessen wrote:

I don't remember such a rule in the 2004 elec code
Yeah, I've been grilled with implementing systems and methods to meet and
exceed U.S. Regulatory CFR, USP/NF, EP, NIST, or whomever dealing with
Standard's and... man... the self regulatory industries like law
enforcement, health care and certain I guess union attorney regulated
agencies rackets can override codes if no one enforces.

My recollection is still National Code to bond meter box to ground. I
even have a wire that was cut by and not re-attached by them, though
something to do with the one Utility Company... Indiana Michigan Power in
my investigation. Code Inspector said the same thing that is unique to
them if I recall correctly.




Re: Can we talk safety for a moment?

Vince Vielhaber
 

Sorry. The meter box. The ground rod had to be near the pole (which I also had to put in).

Vince.

On 02/19/2018 03:24 PM, Richard R. Pope wrote:
Vince,
Which box? The Meter Box or the Main Service panel?
GOD Bless and Thanks,
rich!

On 2/19/2018 11:57 AM, Vince Vielhaber wrote:
I did a new service at a place we used to have up north. I was told
the box was to be grounded with no less than an 8 foot ground rod with
no less than #6 wire, #4 preferred.

Vince.



On 02/19/2018 07:35 AM, John Griessen wrote:
On 02/18/2018 11:35 PM, Richard R. Pope wrote:
Bob,
Not here. The national code states that the meter box has be
ungrounded. If you ground it the Power company won't connect the Power
and the inspector will fail you. I have done several houses and
everyone of them had to have the Meter Box left ungrounded.
Mmm.... uhh... not so sure.... The meter is connected by metal conduit
that is very short distance
to a distribution panel box which is definitely safety GND wire bonded
to box.
So, if there is such a rule, it is about the bonding screws being in a
particular place, not leaving them off.
I don't remember such a rule in the 2004 elec code, which is the most
recent I have studied thoroughly.






Re: Can we talk safety for a moment?

Richard R. Pope
 

Vince,
Which box? The Meter Box or the Main Service panel?
GOD Bless and Thanks,
rich!

On 2/19/2018 11:57 AM, Vince Vielhaber wrote:
I did a new service at a place we used to have up north. I was told the box was to be grounded with no less than an 8 foot ground rod with no less than #6 wire, #4 preferred.

Vince.



On 02/19/2018 07:35 AM, John Griessen wrote:
On 02/18/2018 11:35 PM, Richard R. Pope wrote:
Bob,
Not here. The national code states that the meter box has be
ungrounded. If you ground it the Power company won't connect the Power
and the inspector will fail you. I have done several houses and
everyone of them had to have the Meter Box left ungrounded.
Mmm.... uhh... not so sure.... The meter is connected by metal conduit
that is very short distance
to a distribution panel box which is definitely safety GND wire bonded
to box.
So, if there is such a rule, it is about the bonding screws being in a
particular place, not leaving them off.
I don't remember such a rule in the 2004 elec code, which is the most
recent I have studied thoroughly.




Re: Can we talk safety for a moment?

Glenn Little
 

Refer to MIL HDBK-419
for additional information.
This is available fro free download at many sites.

Glenn

On 2/19/2018 2:08 PM, William Ray wrote:
This is supposed to be a discussion about Tek scopes, and I don't mean to be rude, but safety is kind of important, and so its good to be correct about what's acceptable/unacceptable for wiring practices:

It is quite clear from the 2017 NEC, that water pipes, ground-rods, etc. are still permissible in the USA. I'm not sure if gas pipes ever have been.

"Ufer" grounds require considerably more than 8-feet of conductor in the concrete. 6 AWG is not adequate for a Ufer.

And, technically, _All_ structures that qualify as Grounds based on NEC 250.52(A), must be bonded together, in to a single cohesive grounding electrode system. While possibly semantic, _all_ earth grounds must be collected, connected, and brought to the single Main Service Disconnect point where they are tied to the equipment grounding conductor, and the (grounded conductor) "neutral". So, there may be earth-grounds at multiple physical locations in a system, but they are tied to the _neutral_ at only one point - at the main service disconnect. The equipment-grounding conductor quite often has multiple paths to earth-ground, and this is not a defect.


Barring transcriptional errors, and a few explanatory notes that I left out :

2017 NEC - 250.52 Grounding Electrodes.
(A) Electrodes Permitted for Grounding.

1 Metal Underground Water Pipe.
A metal underground water pipe in direct contact with the earth for 3.0 m (10 ft) or more (including any metal well casing bonded to the pipe) and electrically continuous (or made electrically continuous by bonding around insulating joints or insulating pipe) to the points of connection of the grounding electrode conductor and the bonding conductors. Interior metal water piping located more than 1.52 m (5 ft) from the point of entrance to the building shall not be used as a part of the grounding electrode system or as a conductor to interconnect electrodes that are part of the grounding electrode system.

2. Metal In-round Support Structure(s).
One of more metal in-ground sup[port structure(s) in direct contact with the earth vertically for 3.0m (10 ft) r more, with or without concrete encasement. If multiple metal in-ground support structures are present at a building or a structure, it shall be permissible to bond only one into the grounding electrode system.

3. Concrete-Encased Electrode.
A concrete-encase electrode shall consist of at least 6.0m (20 ft) of either (1) or (2):
(1) One or more bare or zinc-galvanized or other electically-conductive coated steel reinfocing bars or rods of not less than 13mm (1/2 in.) in diameter, installed in one continuous 6.0m (20 ft) length, or if in multiple pieces connected together by the usual steel tie wires, exothermic welding, welding, or other effectve means to create a 5.0m (20 ft) or greater length; or
(2) Bare copper conductor not smaller than 4 AWG...

4. Ground Ring.
A ground ring encircling the building or structure, in direct contact with the earth, consisting of at keast 6.0m (20 ft) of bare copper conductor not smaller than 2 AWG.

5. Rod and Pipe Electrodes.
Rod and pipe electrodes shall not be less than 2.44 m (8 ft.) in length and shall consist of the following materials:
(a) Grounding electrodes of pipe or conduit shall not be smaller than metric designator 21 (trade size 3/4) and, where of steel, shal have the outer surface galvanized or otherwise metal-coated for corrosion protection.
(b) Rod-type grounding electrodes of stainless steel and copper or zinc-coated steel shall be at least 15.85mm (3/8 in) in diameter unless listed.

6. Other Listed Electrodes.

7. Plate Electrodes.
Each plate electrode shall expose not less than 0.186 m2 (2 ft2) of surface to exterior soil.

8. Other Local Metal Underground Systems or Structures.
Other local metal underground systems or structures such as piping systems, underground tanks, and underground metal well casings that are not bonded to a metal water pipe.

250.52
(B) Not Permitted for Use as Grounding Electrodes. The following systems and materials shall not be used as grounding electrodes:
(1) Metal underground gas piping systems
(2) Aluminum
(3) The structures and structural reinforcing steel described in 680.26(B)(1) and (B)(2) (WCR note, this is in reference to structures associated with swimming pools)

NEC - 250.50 Grounding Electrode System.
All grounding electrodes as described in 250.52(A)(1) through (A)(7) that are present at each building or structure served shall be bonded together to form the grounding electrode system. Where none of these grounding electrodes exist, one or more of the grounding electrodes specified in 250.52(A)(4) through (A)(8) shall be installed and used.


--
-----------------------------------------------------------------------
Glenn Little ARRL Technical Specialist QCWA LM 28417
Amateur Callsign: WB4UIV wb4uiv@arrl.net AMSAT LM 2178
QTH: Goose Creek, SC USA (EM92xx) USSVI LM NRA LM SBE ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"


Re: Can we talk safety for a moment?

Ed Breya
 

I agree with what Chuck just said re grounding and NEC. I don't know what the present earth ground quality requirements are, but recall when I replaced the service in one of our houses a few years ago, the old 1960s ground to the water pipe was insufficient, but a new 5/8"D x 8' copper plated steel rod driven into the ground was OK. The inspector just did a visual inspection, complimented my work, and signed off on the permit. The most important of the items was the grounding. Most modern construction I've seen has the box ground wiring attached to a piece of rebar buried in the concrete foundation work.

I think there may be some confusion about box/neutral grounding because of the options available in electrical panels and load centers. These are often built the same - a large box with circuit breakers, sometimes with a large breaker/disconnect, etc. The difference in treatment depends on the application. A service entrance must have the incoming utility neutral and the earth ground tied to the box. Any downstream distribution must have grounding connection all the way back to the service entrance, while the neutral must not be grounded or tied to any of these boxes. Often the difference is in a single screw, included in the parts kit with the box. The neutral bus is insulated, but there's a spot where this screw can be installed to ground neutral to the box at that point. The instructions explain when the screw is to be used or not, but maybe not so clearly, and some people may not understand the difference. The NEC explains it thoroughly, including certain exceptions that normally don't arise in residential wiring, but can in industrial. If you buy a metered service entrance box, there is no ambiguity since it's a dedicated purpose - the earth grounding and neutral lugs are already tied to the box.

Ed


Re: Can we talk safety for a moment?

William Ray
 

This is supposed to be a discussion about Tek scopes, and I don't mean to be rude, but safety is kind of important, and so its good to be correct about what's acceptable/unacceptable for wiring practices:

It is quite clear from the 2017 NEC, that water pipes, ground-rods, etc. are still permissible in the USA. I'm not sure if gas pipes ever have been.

"Ufer" grounds require considerably more than 8-feet of conductor in the concrete. 6 AWG is not adequate for a Ufer.

And, technically, _All_ structures that qualify as Grounds based on NEC 250.52(A), must be bonded together, in to a single cohesive grounding electrode system. While possibly semantic, _all_ earth grounds must be collected, connected, and brought to the single Main Service Disconnect point where they are tied to the equipment grounding conductor, and the (grounded conductor) "neutral". So, there may be earth-grounds at multiple physical locations in a system, but they are tied to the _neutral_ at only one point - at the main service disconnect. The equipment-grounding conductor quite often has multiple paths to earth-ground, and this is not a defect.


Barring transcriptional errors, and a few explanatory notes that I left out :

2017 NEC - 250.52 Grounding Electrodes.
(A) Electrodes Permitted for Grounding.

1 Metal Underground Water Pipe.
A metal underground water pipe in direct contact with the earth for 3.0 m (10 ft) or more (including any metal well casing bonded to the pipe) and electrically continuous (or made electrically continuous by bonding around insulating joints or insulating pipe) to the points of connection of the grounding electrode conductor and the bonding conductors. Interior metal water piping located more than 1.52 m (5 ft) from the point of entrance to the building shall not be used as a part of the grounding electrode system or as a conductor to interconnect electrodes that are part of the grounding electrode system.

2. Metal In-round Support Structure(s).
One of more metal in-ground sup[port structure(s) in direct contact with the earth vertically for 3.0m (10 ft) r more, with or without concrete encasement. If multiple metal in-ground support structures are present at a building or a structure, it shall be permissible to bond only one into the grounding electrode system.

3. Concrete-Encased Electrode.
A concrete-encase electrode shall consist of at least 6.0m (20 ft) of either (1) or (2):
(1) One or more bare or zinc-galvanized or other electically-conductive coated steel reinfocing bars or rods of not less than 13mm (1/2 in.) in diameter, installed in one continuous 6.0m (20 ft) length, or if in multiple pieces connected together by the usual steel tie wires, exothermic welding, welding, or other effectve means to create a 5.0m (20 ft) or greater length; or
(2) Bare copper conductor not smaller than 4 AWG...

4. Ground Ring.
A ground ring encircling the building or structure, in direct contact with the earth, consisting of at keast 6.0m (20 ft) of bare copper conductor not smaller than 2 AWG.

5. Rod and Pipe Electrodes.
Rod and pipe electrodes shall not be less than 2.44 m (8 ft.) in length and shall consist of the following materials:
(a) Grounding electrodes of pipe or conduit shall not be smaller than metric designator 21 (trade size 3/4) and, where of steel, shal have the outer surface galvanized or otherwise metal-coated for corrosion protection.
(b) Rod-type grounding electrodes of stainless steel and copper or zinc-coated steel shall be at least 15.85mm (3/8 in) in diameter unless listed.

6. Other Listed Electrodes.

7. Plate Electrodes.
Each plate electrode shall expose not less than 0.186 m2 (2 ft2) of surface to exterior soil.

8. Other Local Metal Underground Systems or Structures.
Other local metal underground systems or structures such as piping systems, underground tanks, and underground metal well casings that are not bonded to a metal water pipe.

250.52
(B) Not Permitted for Use as Grounding Electrodes. The following systems and materials shall not be used as grounding electrodes:
(1) Metal underground gas piping systems
(2) Aluminum
(3) The structures and structural reinforcing steel described in 680.26(B)(1) and (B)(2) (WCR note, this is in reference to structures associated with swimming pools)

NEC - 250.50 Grounding Electrode System.
All grounding electrodes as described in 250.52(A)(1) through (A)(7) that are present at each building or structure served shall be bonded together to form the grounding electrode system. Where none of these grounding electrodes exist, one or more of the grounding electrodes specified in 250.52(A)(4) through (A)(8) shall be installed and used.


Re: Can we talk safety for a moment?

Vince Vielhaber
 

I did a new service at a place we used to have up north. I was told the box was to be grounded with no less than an 8 foot ground rod with no less than #6 wire, #4 preferred.

Vince.

On 02/19/2018 07:35 AM, John Griessen wrote:
On 02/18/2018 11:35 PM, Richard R. Pope wrote:
Bob,
Not here. The national code states that the meter box has be
ungrounded. If you ground it the Power company won't connect the Power
and the inspector will fail you. I have done several houses and
everyone of them had to have the Meter Box left ungrounded.
Mmm.... uhh... not so sure.... The meter is connected by metal conduit
that is very short distance
to a distribution panel box which is definitely safety GND wire bonded
to box.
So, if there is such a rule, it is about the bonding screws being in a
particular place, not leaving them off.
I don't remember such a rule in the 2004 elec code, which is the most
recent I have studied thoroughly.


34681 - 34700 of 179352