My 1950s era house had a 100amp panel, with a grounding wire that ran to my
well and was clamped to the well casing. I hired a licensed electrician to
upgrade to 200amp panel. He also installed 2-3 ground rods outside the
house and connected from the new panel to them, AS WELL AS running from the
panel via a heavy wire (looks like #6 aluminum strand) clamped to the copper
water pipe downstream of my pressure tank. Notice... he didn't connect to
the well casing, but to the piping on the "house" side of the pressure tank,
and the pressure tank is separated from the well casing by my pump and black
rubber hose (i.e. no electrical continuity). And he left the original
ground wire as-is on the well casing.
Never noticed all this until recently.
Is this correct?
Shouldn't there be a jumper cable to connect across the black rubber hose
(from the copper pipes to the well casing?)
Experienced advice appreciated.
I would not ground to the well casing to avoid possible electrolysis damage.
On Tue, 8 Dec 2015 21:34:32 -0800 (PST), firstname.lastname@example.org wrote:
The well casing is an available electrode and it most be used. The
Grounding Electrode Conductor to water pipes is sized by 250.66 and
should be #4 for your typical 200a service. Since made electrodes like
ground rods are not really that effective, you only need #6, no matter
what the service is. The wire to the isolated interior water pipe is
only bonding the pipe, you should be bonding to the house side of the
plastic so jumper around the water softener.
On Thu, 10 Dec 2015 00:21:14 -0800 (PST), Uncle Monster
like #6 aluminum strand) clamped to the copper water pipe downstream of my pressure tank. Notice... he didn't connect to the well casing, but to the piping on the "house" side of the pressure tank, and the pressure tank is separated from the well casing by my pump and black rubber hose (i.e. no electrical continuity). And he left
the original ground wire as-is on the well casing.
engineering department often requires things that are stricter or over and above that which is in the NEC. I have installed dielectric unions when joining galvanized to copper water pipe then ground clamps on the pipes with a #4 jumper around the dielectric union. The electrical inspection department here is fond of #4 grounding
conductors on everything related to power for residential and light commercial. For telecom and cable systems #14 to #10 in homes but usually #6 to the telecom system backboard ground bars in business and industrial locations. From what I remember for backboard ground bars a #6 grounding conductor to the nearest power system ground
changes the city electrical inspectors want to see but I always had to satisfy them since they had the final say.¯\_(?)_/¯
You size Grounding Electrode Conductors with 250.66 based on the
service conductor size but for the typical 200a service (2/0 copper or
4/0 aluminum conductors) the GEC is #4.
examples with copper
#2 (100a) = #8
#1 or 1/0 (150a) = #6
2/0-3/0 (200a) = #4
Up to 350 kcmil (400a) = #2
Later they refine that by electrode size and when it is a made
electrode you get here
250,66(A) Connections to Rod, Pipe, or Plate Electrodes. Where the
grounding electrode conductor is connected to rod, pipe, or plate
electrodes as permitted in 250.52(A)(5) or (A)(7), that portion of the
conductor that is the sole connection to the grounding electrode shall
not be required to be larger than 6 AWG copper wire or 4 AWG aluminum
note that you can't use aluminum wire within 18" of the dirt so this
really means #6 copper
250.64 (A) Aluminum or Copper-Clad Aluminum Conductors. Bare aluminum
or copper-clad aluminum grounding conductors shall not be used where
in direct contact with masonry or the earth or where subject to
corrosive conditions. Where used outside, aluminum or copper-clad
aluminum grounding conductors shall not be terminated within 450 mm
(18 in.) of the earth.
The largest size required for a Ufer is #4 per 250.66(B) and 250(C)
says a conductor to a ground ring need not be larger than the
conductor in the ring but that is a minimum #2.
It gets even more confusing when you are connecting to interior
If you are talking about water pipe being used as an electrode you
size by 250.66 but if you are just bonding the pipe you use 250.104
that says you size the wire based on the circuit likely to energize
the wire based on 250.122 (the same size as you would use for the
equipment grounding conductor) That could be as small as #14 cu if the
only circuit that gets near it is 15a
Some still read it to say all water pipe bonding shall be sized to
250.66 but if this is not part of the GES, I am not sure how you can
As usual the AHJ generally has the last word so you need to ask your
local guy. Fighting city shall is seldom worth the hassle.
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