Can I use the old flexible conduit?

[gfretwell]

This is more of a theoretical problem than a demonstrated one but the thought is that the extra impedance caused by the spiral wraps in the cable armor might prevent the over current device from operating in a fault condition. I suppose if the cable was long enough it could be a problem tho. The "fix" in AC cable was just a thin strip of the armor material that is actually scrap resulting from the manufacturing process run along with the conductors that effectively shorts out the "choke" created by the armor. The reality is, in 2000, when I tested an old BX job built during WWII, the cable armor still presented less than an ohm if impedance at every receptacle in the building. (Using an Ecos ground impedance tester) To create this "choke" you would need each revolution of the armor to be insulated from the one next to it. Where this is more likely to cause a problem is with point of use surge protectors that require the ground to be effective. The very short duration transients will have trouble being shunted out, even with a fairly low impedance in the armor.

[gfretwell]

Not really true at all. In fact most inspectors have sovereign immunity but the contractors don't. That means if you want to sue the inspector, you are really trying to sue the government. The contractor is still wide open to actions. The fact that an inspector did not find a violation does not insulate the contractor from a negligence suit. That is why they usually have E&O insurance.

[Clare Snyder]

Causes problems with GFCI devices as well, perhaps?? or AFCI?

[Clare Snyder]

And why if they don't, they REALLY should. Particularly in the Litigeous States of America.

It is always possible for even the best tradesman to miss something that on a "bad day" could cause injury or damage that some lawyer could attempt to take everything he owns.

Either insure orbe litigation-proof (own no assetts)

[trader_4]

We have no idea what the extent or purpose of the upgrade is. All he said is that he's planning to re-wire an old home. And yes, he asked if he can use what he thinks is flex conduit. But people quickly pointed out that it's more likely BX cable. In which case the whole idea of reusing it is pointless, because you can't get the old wire out and new wire, including a grounding conductor in. It's nuts.

You then posted this:

"However, If the entire place is actually BX, then the jacket can be very successfully used as a ground conductor between a grounding outlet and a grounding rod. I've done it and have had it done, the ground will be fully confirmed by any and all Wiring Testers, GFCI Affirmers and other testing methods.

Sure, a separate ground wire MAY be better, but only due to matched or

He can't use the jacket of that old BX as the grounding conductor as part of his re-wiring/upgrade, because it does not meet current NEC, unless the cable has the internal bonding wire or a separate ground conductor. Old BX doesn't have it.

My

Again, try following the thread and the question. He's not talking about what exists now, he's talking about REWIRING THE HOUSE. That re-wiring must conform to current NEC.

Citing that a GFCI works, is meaningless. One important use of a GFCI is in circuits with no ground at all, they don't need a ground to function. And what you can test, what you can see, what you think, doesn't change what NEC says.

Again, latest code is nothing but

And of course the whole point is that he's talking about "new stuff". You can't rewire the house and use old BX with no bond wire or separate ground conductor as part of the work. For example, if he's adding another receptacle, he can't do that off the end of the old BX cable. Not only do you have the cable with no ground issue, if the new receptacle is in most living areas, to be NEC compliant, it has to be AFCI protected too.

[trader_4]

You just keep digging the hole deeper. Look at any modern electronics and the incoming power circuitry is always protected by MOVs that are connected from the hot and neutral to ground for surge protection. Same thing on phone line inputs and similar. With no ground, there is nowhere to shunt a surge to before it gets to the electronics. And the quality of the ground matters too, per the above discussion on impedance.

[gfretwell]

I can't think of a reason why it would. Any choke effect of the armor would be common mode affecting the other two conductors and cancel itself out at the GFCI. In fact the coupling into EMT would be a greater effect. The reality is I have one GFCI circuit here feeding lights and receptacles around the back yard that is a few hundred feet long, most in EMT with some RNC and the GFCI is fine with it in spite of all the hysteria I have heard about the coupling problem.

[Clare Snyder]

The issue with the old BX is it works well untill it doesn't. Over time, particularly when in contact with concrete, ow when subjected to moisture, the old BX rusts,and the safety ground circuit CAN become compromized. If and when it does, it is no longer safe - and you don't know it is no longer safe until something happens that requires it to be there - and it's not.

This is why code updates are made, requiring solutions with either less chance of failure, or a more obvious failure mode.

If the old BXcorrodes - not to the point of disintegration and total circuit failkure, but to the point of poor electrical contact from "coil to coil" a 100 ft length of BX becomes effectively a 300 foot long steel (read that as "high resistance" safety ground conductor - not even taking into account the high frequency effect of the "impedence" of the "choke".

[trader_4]

I should have qualified that to say modern electronics that's supplied with a grounded plug. To those electronic appliances, it does matter whether or not you have a ground.

[trader_4]

Burford's experience is limited to the Russian internet troll farm where he lives in the basement. Do they even have inspectors there?

[Mark]

BX was outlawed in Chicago I believe because people would cut the wires at the same time as the shield so now you use greenfield and add the wires after the shield is cut.

[gfretwell]

Most of the things you are talking about only have 2 wire line cords so the ground is not important at all for any internal protection. The MOV connects line to neutral, usually with a 250v or so MOV. When you have a connection (antenna, satellite, cable or phone) you should have primary inlet protection. This is best done at the interface where it comes into the house, connected to the service ground but having supplemental protection at the equipment may do some good too. That might be compromised by the BX, depending on exactly how much impedance the armor creates. I doubt it is worth ripping out walls to fix it tho. If this is really a concern, you can always fish Romex to those few receptacles. Most of the stuff in your house will not be affected at all.

[Clare Snyder]

I was thinking more GFCI outlets - not breakers - not feed-through

--- but still just a question.

[trader_4]

I agree and that's why I made my follow on post. But electronics that do have a grounded plug, eg computers, laser printer, dishwasher, refrigerator, washer, dryer, will typically have MOVs that shunt to ground and the electronics in those will benefit from the protection.

[bud--]

Why do you think that? Particularly in the '50s.

Best? Better than what

True for most any wiring.

So never use Romex? Did "your friend" suggest using exposed Romex?

So my house, which was originally rigid pipe, should only have rigid pipe extensions?

[bud--]

If trader's post was repeated I could tell what Iggy was talking about. But morons using HomeMoanersHub never repeat what they are responding to.

So the ground resistance back to the panel is 100 ohms. The testers use maybe 1 mA to test the ground [and other] wires. That gives a voltage drop of 0.1 V. So the ground is obviously entirely adequate for, say, a

5 amp ground current.

Plug in testers are very effective in testing whether you have a good ground connection.

It is the kind of opinion that makes everyone value the HomeMoanersHub.

[bud--]

A repeat of the expected quality of advice from HomeMoanersHub.

(It is actually rather easy to test ground quality.)

Not exactly.

Like for the common maintenance of replacing a receptacle:

- if the NEC requires an added receptacle be GFCI protected, the replacement must be GFCI protected

- if the NEC requires an added receptacle be AFCI protected the replacement must be AFCI protected

- if the NEC requires an added receptacle be 'childproof' the replacement must be 'childproof'

- if the NEC requires an added receptacle be weather resistant the replacement must be weather resistant.

[bud--]

I always heard it was the resistance of the much longer length of much smaller cross-section, maybe low conductivity steel, if the spiral did not bond to the adjacent spirals. But impedance includes more.

Those protectors do not work primarily by earthing a surge. They work primarily by clamping the voltage on ALL the wires going to protected equipment to the 'ground' at the protector.

If you have H-N-G Romex, and there is 6kV at the panel, you have H supplying the protector and H-G sinking the surge. The voltage of the 'ground' at the protector will be about 2kV with respect to the 'ground' at the panel. But the voltage from ALL the wires to the protected equipment is limited to a safe value.

Because a 'surge' is a very short duration event, there are relatively high frequency current components. That means the inductance of wires (H, N & G) is more important than the resistance. The current, and thus energy, that can reach a point of use protector is surprisingly small.

The likely much larger current from the panel to the earthing electrode(s) is similarly limited, and the panel 'ground'-to-earth voltage may be very high.

(You probably agree with most or all of this.)

Protection is not primarily by shunting to earth.

If you have only H and N as effective conductors, there is H supplying the protector and N sinking the surge. If there is 6kV at the panel the voltage of the 'ground' at the protector will be about 3kV with respect to the 'ground' at the panel. But the voltage between the wires to the protected equipment is still limited to a safe value.

============================================= If an electrician suggests pulling Romex into flex (other than limited special circumstances) their opinions are not worth listening to.

BX has always been a tradename for an example of type AC wiring.

IMHO a circuit wired in old BX can be extended. (Your opinion?)

(The extension would often have to be AFCI protected. One method (which may not be the best) is to wire it through an AFCI receptacle where the new part of the circuit originates.)

[gfretwell]

A good ground impedance tester verifies

[gfretwell]

We basically agree on the surge protection

If you follow the NEC rules the AFCI has to be at the first receptacle in the circuit if you are not using an AFCI breaker. If you do not have an effective ground path and you want to use 3 wire receptacles you need GFCI protection.