Replacing ungrounded with grounding outlets

[rusty monkey]

My house was built in 1962 and originally wired with two wire armored cable with the bonding strip (no ground wire). The bedrooms have two prong outlets that I want to replace with three prong. If the armored cable and bonding strip are intact all the way back to the main panel, can I pigtail a ground wire from the ground screw on the outlet to the box and have a proper ground?

 

[rockwithjason]

it wouldn't be code compliant but yes if the continuity is intact you can make a ground that way for practical purposes. for it to be code you would have to run a 12ga wire all the way back to the panel i believe

 

[nadogail]

GFCI outlets, in my opinion, would be better than ordinary 3 prong outlets.

 

[Kevin54]

It was my understanding that if you had the armored cable (flexible metallic outer cable) that you can install a grounded outlet, then the ground wire can be ran to the metallic jacket but somewhere a ground rod has to be driven into the ground and then a wire off of the metallic jacket to the ground rod. Or was this something that could have been done a few years back but not now? Or did I miss the complete thing by about 17 miles?

 

[rockwithjason]

um.... 16.5 miles to be exact. lol. if you want to split hairs and be 100% code compliant then you have several options. you can use gfi outlets and mark them "no ground", you can use 3 wire outlets supplied by the gfi and mark them "no ground" or you can install a ground wire to any of the points listed in 250.130c which basicly says to connect it anywhere on the grounding electrode system. you never connect to an independent ground rod unless that ground rod is bonded to all other ground rods in the system with the proper size wire.

 

[mrb]

It was my understanding that if you had the armored cable (flexible metallic outer cable) that you can install a grounded outlet, then the ground wire can be ran to the metallic jacket but somewhere a ground rod has to be driven into the ground and then a wire off of the metallic jacket to the ground rod. Or was this something that could have been done a few years back but not now? Or did I miss the complete thing by about 17 miles?

you need a proper ground and it must be bonded to the neutral at the point of service. The point of grounding is to give the electricity a path back to the source so the breaker will trip under a fault condition. If you put in a grounded receptacle, connect its ground to a water pipe and the water piping in the house isnt properly bonded to the service, if you have a fault or short circuit on something plugged into that receptacle you will electrify all the water pipes in the house and since a breaker wont trip you wont know anything is wrong until its too late....

I recommend installing GFI recpetacles marked no ground present for the safest installation over anything jerry riggged or trying to use the cable armor as the ground without a qualified individual making sure everything is kosher.

 

[sberry]

then the ground wire can be ran to the metallic jacket but somewhere a ground rod has to be driven into the ground and then a wire off of the metallic jacket to the ground rod.

Yup, again, the ground rod has nothing to do with it in this case.

 

[Mike83]

rusty monkey,
My house is 1960 (and in Greendale btw, so we're practically neighbors) and had all two prong outlets. I replaced every one with regular three prong and since the BX cable is grounded to the box, the screws holding in the receptacle provide a ground path. Buy one of those testers you plug into the receptacle and it will diagnose an open ground, reverse polarity, etc. etc. I also installed GFCIs in the bathrooms, garage, kitchen and outdoors. Everything is kosher as far as I can tell.

You can even double check the outlet by sticking an electrical tester (the one with the light) into the line side and touch one of the screws holding the receptacle (not the cover) and it should light up proving that current can travel to ground. Since this worked for me I did not pigtail a ground wire from the receptacle to the box.

Finally, my system is grounded to the water pipes. Just ensure that there are jumpers around stuff that does not conduct electricity!

ps GFCI outlets cost $12.00. Regular receptacles cost 29 cents or something like that

 

[tfi racing]

rusty monkey,
Since this worked for me I did not pigtail a ground wire from the receptacle to the box.

I don't have an issue with using the bonding strip in your old bx as a ground,although now not code compliant,at one time it was and should be allowed to be grandfathered.It is better than the options,rewiring the house or having no grounded receptacles at all.However your receptacles must have a wire bonding them to the box,the screws cannot be relied on for bonding continuity.

 

[mrb]

the screws cannot be relied on for bonding continuity.

unless the receptacle is of the 'self grounding' type that has the metal tab that grabs the screw. (pigtailing a ground is still better though -but sometimes the old boxes have nowhere to attach one)

 

[Mike83]

unless the receptacle is of the 'self grounding' type that has the metal tab that grabs the screw. (pigtailing a ground is still better though -but sometimes the old boxes have nowhere to attach one)

Yes, the boxes have the metal tabs that get screwed into. There is nowhere to attach a ground wire to the box, but I do have those little green clamps to pinch the wire onto the edge of the box. Those would be another option. I think I used those for installing a bathroom fan.