Electrical code ? Wire type indoor vs buried

[JPRambo]

No MC cannot be buried.

 

[dickfoster]

Just curious, can this be dine when retrofitting a house with 2 conductor outlets?

I've often wondered how one would go about it besides total rewiring of the home.

Many older homes with two prong outlets were wired with BX armored cable and the outer BX shield is the ground. Install a 3 prong outlet using a metal box. THe existing box is likely metal. The metal box clamps to the outside armored shield so connect your ground prong to the metal box as per normal. Also ensure that the metal panel is grounded and that all the BX cables are clamped to the metal panel housing so they are grounded too.


This is BX cable.

http://www.diychatroom.com/attachme...ding-using-armored-cable-ok-armored_cable.jpg

 

[buickanddeere]

Many older homes with two prong outlets were wired with BX armored cable and the outer BX shield is the ground. Install a 3 prong outlet using a metal box. THe existing box is likely metal. The metal box clamps to the outside armored shield so connect your ground prong to the metal box as per normal. Also ensure that the metal panel is grounded and that all the BX cables are clamped to the metal panel housing so they are grounded too.


This is BX cable.

http://www.diychatroom.com/attachme...ding-using-armored-cable-ok-armored_cable.jpg

Not allowed. The outer spiral sheath of the BX cable just turns into a red hot heating element when a line shorts to "ground".

 

[JPRambo]

The outer 'shell' of BX is not suitable for a grounding path. In a ground fault condition it can act as a type heater.

 

[dickfoster]

Not allowed. The outer spiral sheath of the BX cable just turns into a red hot heating element when a line shorts to "ground".

One would think a fuse or breaker would take care of that. I know I've seen it done.

 

[aczlan]

One would think a fuse or breaker would take care of that. I know I've seen it done.

What you have to do (if you can't replace the wire) is to put in a GFCI, either as the first outlet in the circuit, or at the breaker. Then you put stickers on the following outlets that say "no equipment ground" (should come in with a GFCI outlet).
The way a GFCI works is to compare the power going out via the hot leg to the power coming back in via the neutral and if they don't match exactly, it trips.

Aaron Z

 

[ultrarunner]

We have a lot of BX dating from the 1950's where the armor is used as ground...

I'm guess it must have been permissible at one time... even if it was 50+ years ago?

 

[buickanddeere]

We have a lot of BX dating from the 1950's where the armor is used as ground...

I'm guess it must have been permissible at one time... even if it was 50+ years ago?

We know better now after the fires .

 

[Zerk]

Anything in an Attic worries me. Especially as far as mice are concerned. Any new wiring in my outbuildings is done in conduit or BX.

Attics are full of romex. Not to mention the mice in the basement, and romex.

 

[grsthegreat]

Just FYI, you can also ground locally at the remote structure, just remove the bonding at the remote panel and drive an 8' ground rod. That will save you a lot of money on ground wire.

No you cant. NEC requires a ground wire. Most jurisdictions also frquire an additional ground rod at remote structure

 

[kcflhrc]

No you cant. NEC requires a ground wire. Most jurisdictions also frquire an additional ground rod at remote structure

Previous codes allowed it. Not all structures are up to current NEC code so yes, you can still do it unless someone is going to inspect it.

 

[kcflhrc]

A4. The practice of bonding the grounded (neutral) conductor to the equipment enclosure is only permitted by 250.32(B)(2) where

(1) an equipment grounding conductor is not run with the supply to the building or structure, and

(2) there are no continuous metallic paths bonded to the grounding system in both buildings or structures involved, and

(3) ground-fault protection of equipment has not been installed on the common ac service, and

(4) the size of the grounded conductor shall not be smaller than the larger of:

That required by 220.22 (maximum unbalanced neutral load), or

That required by 250.122 (equipment grounding conductor size).


When an equipment grounding conductor is not run to a separate building or structure, the grounded (neutral) conductor must be used to provide the effective ground-fault current path required to clear any ground-faults (line-to-case faults) in addition to carrying any unbalanced neutral current [250.4(A)(3)].

 

[buickanddeere]

Previous codes allowed it. Not all structures are up to current NEC code so yes, you can still do it unless someone is going to inspect it.

Given that line of reasoning. It would be fair game to wire a house with two wire without a ground and use two slot receptacles .

 

[kcflhrc]

Given that line of reasoning. It would be fair game to wire a house with two wire without a ground and use two slot receptacles .

Your line of reasoning would still make seat belts optional. Way off track from what we are talking about.

 

[ultrarunner]

Most of what I deal with residential was built during the 1920's building boom... still working as intended soon to be a 100 years later... several homes still have a single 30 amp Edison Fuse Main and some have two fuses because the neutral is also fused... just the way things were done with a permit back then... the electricians must have done a good job with nearly a century of service.

Of course the Hospital is all EMT or BX with Ground wire and some isolated grounds, etc... it has a 1995 Certificate of Occupancy and the measured actual load is about 200 amps on 1200 amp service.

The 1920's homes are close to max much of the time... yet I lived in one for several years and never blew the main... 1200 square feet 3 bedrooms.

I do like the discussions we have here... always learning how to improve and it is interesting how many regional customs and practices there are are.

 

[kcflhrc]

I think the confusion is what was acceptable prior to the new code and what is just plain wrong. Big difference.

 

[ultrarunner]

Yes... and I do run into that... like seeing were someone used copper pipe in place of EMT.

Helped a friend yesterday that was having clothes dryer problems... house built in 1955.

Some added a length of copper wire to extend the 220v dryer circuit a few feet by twisting the ends together in the crawl space... it was also #10 and city code requires a minimum of #8... plus no junction box was used.

A right way and wrong and and an old way...

 

[JPRambo]

#8 to a dryer? 30 amp?

 

[ultrarunner]

Yes... has been city code since before I was born... #8 Copper

 

[Zerk]

#10 copper to a dryer. NEC. Not #8