Reuse UFER ground?

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rszimm

Member
Location
Tucson, AZ
Doing a 200->400A upgrade. There's an existing UFER ground wire that's #4 coming into the panel that runs right into the footer. My reading of NEC seems to state that #4 is fine for UFER ground, but 250-66 seems to indicate that I need #2 (350 kcm service wires). Which is correct?

Also, was told that the local town won't accept a UFER ground on a panel upgrade because they can't see that the part inside the footer has been done properly, so it might be a moot point.
 

jumper

Senior Member
A direct connected UFER GEC never needs to be larger than #4.

250.66
(B) Connections to Concrete-Encased Electrodes.
Where the grounding electrode conductor is connected to a single
or multiple concrete-encased electrode(s) as permitted in
250.52(A)(3), that portion of the conductor that is the sole
connection to the grounding electrode(s) shall not be re-
quired to be larger than 4 AWG copper wire.

If the original UFER passed inspection then it should still be fine. Still an AHJ/inspector call.
 

rszimm

Member
Location
Tucson, AZ
Ill ring the inspector. I think the house was built before the town took over this area, so maybe they just don't trust the old county inspectors.

OK, so the next question is if I can splice that #4 with a permanent splice if it's a few inches too short to reach the bar on the new panel?
 

iwire

Moderator
Staff member
Location
Massachusetts
Ill ring the inspector. I think the house was built before the town took over this area, so maybe they just don't trust the old county inspectors.

OK, so the next question is if I can splice that #4 with a permanent splice if it's a few inches too short to reach the bar on the new panel?

Yes you can splice.

And if you don't have a permanent splice just drive a ground rod and use it as the splice.
 
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rszimm

Member
Location
Tucson, AZ
And if you don't have a permanent spice just drive a ground rod and use it as the splice.
Yeah, already bent 3 ground rods trying to get one into the ground. Nothing but granite rocks up here with a bit of sand in between them. First one was straight up. Next 45 degrees. Next a foot away straight up. Then I gave up and decided to try and use the UFER if possible.
 

MasterTheNEC

CEO and President of Electrical Code Academy, Inc.
Location
McKinney, Texas
Occupation
CEO
OK, so the next question is if I can splice that #4 with a permanent splice if it's a few inches too short to reach the bar on the new panel?

250.64(C) Continuous. Except as provided in 250.30(A)(5) and(A)(6), 250.30(B)(1), and 250.68(C), grounding electrode
conductor(s) shall be installed in one continuous length without
a splice or joint. If necessary, splices or connections shall be
made as permitted in (1) through (4):
(1) Splicing of the wire-type grounding electrode conductor
shall be permitted only by irreversible compression-type
connectors listed as grounding and bonding equipment
or by the exothermic welding process.
(2) Sections of busbars shall be permitted to be connected
together to form a grounding electrode conductor.
(3) Bolted, riveted, or welded connections of structural metal
frames of buildings or structures.
(4) Threaded, welded, brazed, soldered or bolted-flange
connections of metal water piping.

Have at it....
 

dionysius

Senior Member
Location
WA
Doing a 200->400A upgrade. There's an existing UFER ground wire that's #4 coming into the panel that runs right into the footer. My reading of NEC seems to state that #4 is fine for UFER ground, but 250-66 seems to indicate that I need #2 (350 kcm service wires). Which is correct?

Also, was told that the local town won't accept a UFER ground on a panel upgrade because they can't see that the part inside the footer has been done properly, so it might be a moot point.
Why not measure resistance to ground for the UFER and validate its usage????
 

iwire

Moderator
Staff member
Location
Massachusetts
Why not measure resistance to ground for the UFER and validate its usage????

What value is acceptable?

The NEC does not require a minimum resistance value for concrete encased electrodes (CEE).

The NEC does require a CEEs be made of certain size, length and placed conductors which can only be verified by direct observation.
 

kwired

Electron manager
Location
NE Nebraska
What value is acceptable?

The NEC does not require a minimum resistance value for concrete encased electrodes (CEE).

The NEC does require a CEEs be made of certain size, length and placed conductors which can only be verified by direct observation.
Good question on what is acceptable.

OP has no idea what this 4 AWG does once it enters the concrete either though.

Is there water pipe or building steel available? If so I wouldn't worry about what may be in the concrete - but still would connect it.
 

rszimm

Member
Location
Tucson, AZ
Figured I'd update everyone with what the inspector said. Generally they frown on reusing UFER because most people just hook it up, point to the wire coming out of the wall, and say "it's the UFER". They're fine with reusing UFER so long as at least one of two requirements are met:
1. They need to see the wire coming out of the foundation and that it hasn't been compromised in any way.
2. We can verify 25 ohms to ground.

I managed to do both (dug up the UFER and showed it going into the footer, and tested continuity to an exposed rebar on the other side of the house). So check.
Now just a little cadweld one shot on the UFER to extend it another foot and I'm good.
 

kwired

Electron manager
Location
NE Nebraska
Figured I'd update everyone with what the inspector said. Generally they frown on reusing UFER because most people just hook it up, point to the wire coming out of the wall, and say "it's the UFER". They're fine with reusing UFER so long as at least one of two requirements are met:
1. They need to see the wire coming out of the foundation and that it hasn't been compromised in any way.
2. We can verify 25 ohms to ground.

I managed to do both (dug up the UFER and showed it going into the footer, and tested continuity to an exposed rebar on the other side of the house). So check.
Now just a little cadweld one shot on the UFER to extend it another foot and I'm good.

That is what I have a problem with and it has already been brought up in this thread.

If this were new construction and a new CEE - do they require you to verify 25 ohms? I bet not. If they do what is their justification for doing so, it is not directly from NEC if they have something.

In AZ I can imagine there are CEE's that can't meet 25 ohms.

I don't have so much issue with the practice of driving a ground rod(s) if unsure of what may be in the concrete. Chances are if they did anything even halfway correct in the CEE it will still have lower resistance then two rods will though.
 

rszimm

Member
Location
Tucson, AZ
If this were new construction and a new CEE - do they require you to verify 25 ohms? I bet not. If they do what is their justification for doing so, it is not directly from NEC if they have something.
I think the justification is that in new construction presumably someone saw the UFER being physically installed before the concrete was poured, and saw the #4 routing from that point through the wall to the panel location. In a retrofit, all you've got is a random #4 copper coming out of the wall and they need some sort of assurance that the wire actually goes to ground, and isn't, for instance, a bonding conductor, or something that got cut or damaged in some way. If you can't get 25 ohms, then uncover the full length of the wire and show that it actually dives into the foundation. Seems somewhat reasonable to me.
 

kwired

Electron manager
Location
NE Nebraska
I think the justification is that in new construction presumably someone saw the UFER being physically installed before the concrete was poured, and saw the #4 routing from that point through the wall to the panel location. In a retrofit, all you've got is a random #4 copper coming out of the wall and they need some sort of assurance that the wire actually goes to ground, and isn't, for instance, a bonding conductor, or something that got cut or damaged in some way. If you can't get 25 ohms, then uncover the full length of the wire and show that it actually dives into the foundation. Seems somewhat reasonable to me.

I know breaking out concrete is unreasonable, but 25 ohms on a proper CEE might not be unreasonable either.

With the ground rods and the 25 ohm rule you drive one and if it is more then 25 ohms you drive another one - if you still are over 25 you don't have to drive anymore, or you just drive two rods and don't bother with measurements. Even if that leaves you with 100 ohms, that is all that is required. Building steel electrode? you are required to bond to it regardless of what it's resistance is as well.

I don't know what a typical CEE resistance is, but would not be surprised if you can't catch one at the right time in AZ that is 25 ohms or more, but other times may be less. I do know they will typically be less resistance than a ground rod, even if they are not quite done to code - there is just a lot more surface contact with earth and that makes them lower resistance in general.
 
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