2-Wire NM..

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B4T

B4T

Senior Member
Location
Long Island, N.Y.
I have a customer who has the old NM with no ground..

Easy fix is installing GFCI receptacles where needed..

My question is what happens when you have equipment like a computer that has a 3-wire cord..

What are the problems with missing ground.. if any..
 
B4T said:
Does the missing ground cause any performance issues is the big question..
Click to expand...
Sometimes. I recently had a data acquisition system which used a PC chassis (USB port) as signal ground. The power supply had filter caps from both sides of the line to "ground". Plugged into an ungrounded outlet put 60VAC on my computer chassis and on analog 0V which was way out of common mode capability.

Danger ... MAYBE ... messy, yeah.
 
B4T said:
I realize that.. but the GFCI protects you from a shock hazard..

Does the missing ground cause any performance issues is the big question..
Click to expand...

No, the grounding conductor has no bearing on computer performance. That is a wives tale that persists in the industry. All the grounding conductor does is connect metallic paths and parts back to the source, nothing more.
 
B4T said:
I have a customer who has the old NM with no ground..

Easy fix is installing GFCI receptacles where needed..

My question is what happens when you have equipment like a computer that has a 3-wire cord..

What are the problems with missing ground.. if any..
Click to expand...

A computer is also known as information technology equipment. See 250.114(3) and(4).



By the way I agree with Peter D
 
iwire said:
A computer is also known as information technology equipment. See 250.114(3) and(4).
Click to expand...

OK.. so I need to fix the problem..:thumbsup:

Directly under the receptacle is BB heat.. I read this section as allowing me to connect a grounding conductor to HWP.. it does not say hot or cold in 250.50..

(C) Nongrounding Receptacle Replacement or Branch
Circuit Extensions. The equipment grounding conductor
of a grounding-type receptacle or a branch-circuit extension
shall be permitted to be connected to any of the following:
(1) Any accessible point on the grounding electrode system
as described in 250.50
 
B4T said:
OK.. so I need to fix the problem..:thumbsup:

Directly under the receptacle is BB heat.. I read this section as allowing me to connect a grounding conductor to HWP.. it does not say hot or cold in 250.50..

(C) Nongrounding Receptacle Replacement or Branch
Circuit Extensions. The equipment grounding conductor
of a grounding-type receptacle or a branch-circuit extension
shall be permitted to be connected to any of the following:
(1) Any accessible point on the grounding electrode system
as described in 250.50
Click to expand...

Then I reckon you'll have to put bonding jumpers on all your zones and water feed at the boiler (in case it gets replaced).................oh my

plus, is BB really part of the grounding electrode system?
 
ritelec said:
plus, is BB really part of the grounding electrode system?
Click to expand...

Hot and cold are connected to metal either at boiler or water heater.. IMO.. :roll:


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 conductor(s) or jumper(s), if installed.
 
B4T said:
Hot and cold are connected to metal either at boiler or water heater.. IMO.. :roll:


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 conductor(s) or jumper(s), if installed.
Click to expand...

I think it would be easier to sell a new circuit:thumbsup:
 
peter d said:
No, the grounding conductor has no bearing on computer performance. That is a wives tale that persists in the industry. All the grounding conductor does is connect metallic paths and parts back to the source, nothing more.
Click to expand...

My thoughts also. What does the power cord go to on a typical computer - directly to a power supply that has the secondary isolated from the primary. How many notebooks, netbooks, tablets, etc. don't even have a grounding type plug on the supply cord? - almost all of them.

B4T said:
OK.. so I need to fix the problem..:thumbsup:

Directly under the receptacle is BB heat.. I read this section as allowing me to connect a grounding conductor to HWP.. it does not say hot or cold in 250.50..

(C) Nongrounding Receptacle Replacement or Branch
Circuit Extensions. The equipment grounding conductor
of a grounding-type receptacle or a branch-circuit extension
shall be permitted to be connected to any of the following:
(1) Any accessible point on the grounding electrode system
as described in 250.50
Click to expand...

Only the first 5 feet of water pipe entering a building is a part of the grounding electrode system.
 
B4T said:
Hot and cold are connected to metal either at boiler or water heater.. IMO.. :roll:


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 conductor(s) or jumper(s), if installed.
Click to expand...

(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.
Click to expand...

You might want to consider the part in red. If where you plan on connecting to the water pipe is not within 5' of entry to the house, I don't think you can according to this.


Kwire, your post hadn't showed up when I posted, sorry!
 
Last edited:
kwired said:
My thoughts also. What does the power cord go to on a typical computer - directly to a power supply that has the secondary isolated from the primary. How many notebooks, netbooks, tablets, etc. don't even have a grounding type plug on the supply cord? - almost all of them.



Only the first 5 feet of water pipe entering a building is a part of the grounding electrode system.
Click to expand...

Yep.. I just found that section.. :(



(C) Metallic Water Pipe and Structural Metal. Grounding
electrode conductors and bonding jumpers shall be permitted
to be connected at the following locations and used
to extend the connection to an electrode(s):

(1) Interior metal water piping located not more than 1.52 m
(5 ft) from the point of entrance to the building shall be
permitted to be used as a conductor to interconnect electrodes
that are part of the grounding electrode system.
 
B4T said:
Hot and cold are connected to metal either at boiler or water heater.. IMO.. :roll:
Click to expand...

Yes, domestic hot and cold............but not hots at the boiler..........if the boiler were removed............but........you ran into a wall with the 5' anyway. Sorry.

Question about the 5'? I have to run and will look into when I return, but is not grounding to the water pipe "anywhere" acceptable in commercial?
What if the owner makes and sells pottery?
 
ritelec said:
Question about the 5'? I have to run and will look into when I return, but is not grounding to the water pipe "anywhere" acceptable in commercial?
What if the owner makes and sells pottery?
Click to expand...

Yes.. here is the exception..

Exception: In industrial, commercial, and institutional
buildings or structures, if conditions of maintenance and
supervision ensure that only qualified persons service the
installation, interior metal water piping located more than
1.52 m (5 ft) from the point of entrance to the building shall
be permitted as a bonding conductor to interconnect electrodes
that are part of the grounding electrode system, or as
a grounding electrode conductor, if the entire length, other
than short sections passing perpendicularly through walls,
floors, or ceilings, of the interior metal water pipe that is
being used for the conductor is exposed.
 
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