Replacing old 2-prong plug HELP

Hello. I need to replace an old 2-prong outlet, with a 3-prong—so that i can use a 12,000 BTU window A/C. I dont know if the box is grounded, im assuming not. So, can I/should i install a GFCI 3-prong outlet? And if so, should I attached a ground wire? OR, should I go with a standard 3-prong outlet, and add a ground wire?

Thanks in advance for the help


the gfci will only wrk if there's a grounding wire

Depending on how old the wiring is, it's possible there is a grounding wire to the box, or possibly shielded cable acting as a ground

I do a lot of electric work myself, but if there's any doubt, safety first and call an electrician!



It is fairly likely that the circuit may not support an AC unit, no matter what type of outlet you have.  I agree re calling an electrician.


Would highly recommend Superior Wirework. They have lots of clients in the area, me included. 973-713-5345, ask for the owner -- Dan. Reputable, on time and competitive prices.


Much of the old wiring around here doesn't have a ground wire anyway.

You can always just use an adaptor to go from the 3-prong plug to the 2-prong outlet.


thanks all. I thought about using the adaptor and just screwing the ground into the plate, i've done that on smaller BTU units in other rooms and seems fine.


I had read that GFCI will work without a ground wire. Supposedly that's what it was designed for. Am i wrong here?


thanks


a fault in an appliance will not trip the GFCI, but an unbalanced load will.  If the box is getting a ground through BX you will probably be okay.



FilmCarp said:

a fault in an appliance will not trip the GFCI, but an unbalanced load will.  If the box is getting a ground through BX you will probably be okay.

thank you. Is there an easy way to tell if the box is grounded? I have a pig tail tester but not sure exactly how to tell. And if I added a ground wire anyway, just to be "safe", and installed the GFCI would that be OK? or should i just go with a standard 3-prong?


if you meter from hot to the box, you will get 110 volts if the box is grounded.  But I still want to say that I don't like this.  If you get a good reading, but two years from now change something else up the line you may lose the ground.



FilmCarp said:

if you meter from hot to the box, you will get 110 volts if the box is grounded.  But I still want to say that I don't like this.  If you get a good reading, but two years from now change something else up the line you may lose the ground.

thanks. maybe i should just call someone and ask/have them do it? I thought it would be an easier DIY project oh oh


I always think when something is iffy and inside the walls (i.e., plumbing and electric), it makes sense to call in someone who does this for a living! Hence my electrician's contact info above... 



FilmCarp said:

if you meter from hot to the box, you will get 110 volts if the box is grounded.  But I still want to say that I don't like this.  If you get a good reading, but two years from now change something else up the line you may lose the ground.

Indeed.  In some of these houses a ground was achieved by tying in to a cold water pipe, for instance.  If there's a plumbing change (like disconnecting an unused pipe from the system so it's no longer grounded) you have no more ground.  But frankly that's something that can happen in any house with any outlet unless you've completely rewired and know how all the circuits work.  For instance I found that even though I have a lot of BX cable in my house (which theoretically should be grounded), some of it traced back to knob and tube wiring!  No ground there.

If you get a two prong to three prong adapter, make sure you unscrew the faceplate of the outlet and re-screw it in through the little loop in the adapter.  Then you can check and see if you have a grounded connection with your pigtail tester.

Just a thought.


If your electric panel has breakers, you could replace this circuit with a GFCI breaker for the entire load. That doesn't solve your grounding wire issue though. And as other have posted, the original wiring may not be appropriate for the draw 12,000 but will create.

Our home is circa 1907, and we ended up running separate 20a service to our window AC. Because the walls were balloon construction, running the new electric was just snaked through the wall to the basement. Cant remember the cost, but don't think it was super expensive.



The A/C is currently being run in the next room without issues. Granted it's a standard 3-prong outlet, and I have no idea what the load is for the breaker box, downstairs in the basement. 

Is there an easy way to tell what the breaker is rated at, to decide if this could work with the adaptor on the face plate?


The breaker should be marked, typically 15a/20a/ or 30a. A lot of our circuits are only 15a if its running outlets and lights. The issue is not so much the breaker, but the wiring itself. There are differently rated depending on what is on the circuit. So for example, kitchen appliance circuit should be heavier gage than living room lights. If you run a heavier load on the lower rated wiring you run the risk of heating the wires, damaging the insulation and potentially starting a fire.

I don't want to be doom and gloom though, you may be perfectly fine to install a new grounded outlet and run it in the new room, but I would not do the adapter screwed into the face plate only unless you know for certain that the box is grounded.

Many older homes in the area have armored 2 wire systems (BX) which have been retrofitted to ground the circuit through the metal sheath. This is actually not to code per NEC. It might worth having someone take a look at the outlet you currently have it plugged into to make sure that one is correctly grounded. 

The typical home inspection often doesn't turn this up, because they just use a tester on the system, and often do not remove face plates to look at the work inside the box.

Probably way more detail than needed or asked for...



rowerg said:

The breaker should be marked, typically 15a/20a/ or 30a. A lot of our circuits are only 15a if its running outlets and lights. The issue is not so much the breaker, but the wiring itself. There are differently rated depending on what is on the circuit. So for example, kitchen appliance circuit should be heavier gage than living room lights. If you run a heavier load on the lower rated wiring you run the risk of heating the wires, damaging the insulation and potentially starting a fire.

I don't want to be doom and gloom though, you may be perfectly fine to install a new grounded outlet and run it in the new room, but I would not do the adapter screwed into the face plate only unless you know for certain that the box is grounded.

Many older homes in the area have armored 2 wire systems (BX) which have been retrofitted to ground the circuit through the metal sheath. This is actually not to code per NEC. It might worth having someone take a look at the outlet you currently have it plugged into to make sure that one is correctly grounded. 

The typical home inspection often doesn't turn this up, because they just use a tester on the system, and often do not remove face plates to look at the work inside the box.

Probably way more detail than needed or asked for...

^ this is actually really well said, thank you for the details! I was thinking of actually grounding the box, just to be sure. I watched a Youtube video oh oh  Seriously, it doesn't look that hard to do, am I totally off here? Regardless, I do think I will have someone come look, just to be totally sure and safe. Thanks again for this


I think this is totally DYI able. Just remember to turn off the power. Nothing like getting buzzed by a live line. You can pick up an outlet tester for a couple of bucks to make sure the ground is working. Looks like a big yellow plug with three little lights on it. The pattern or color will tell you if the outlet is connected correctly. BTW- i probably should have stated I am not an electrician, but have been dealing with my old home for about 8 years now and faced this same issue.



rowerg said:

I think this is totally DYI able. Just remember to turn off the power. Nothing like getting buzzed by a live line. You can pick up an outlet tester for a couple of bucks to make sure the ground is working. Looks like a big yellow plug with three little lights on it. The pattern or color will tell you if the outlet is connected correctly. BTW- i probably should have stated I am not an electrician, but have been dealing with my old home for about 8 years now and faced this same issue.

I was going to get one of those, but all of them seem to be 3-pronged testers. Can you use an adaptor on it? or does that not work?


frankly, If i had to ask, i would hire a handyman (cheaper and more likely to take the job than an electrician--i have a 1 hour job that I actually need an electrician for but no one will do it for less than $1000)...it is a DIY if you are handy..but not everyone is--my issue is my dexterity, I just don't trust myself with wires.  to just switch to a regular 3 prong  is a simple swap out, GFCI is more involved.


there are adapters, but I would not use an adapter with an AC.

and yeah, if there has never been an AC there, you will have to see what else is on the circuit...any individual outlet should be able to support an AC, BUT if there is anything else on the circuit, that can over load it.  I used to have an AC on a shared circuit...i could not run anything other than a light or clock at the same time...



jmitw said:

frankly, If i had to ask, i would hire a handyman (cheaper and more likely to take the job than an electrician--i have a 1 hour job that I actually need an electrician for but no one will do it for less than $1000)...it is a DIY if you are handy..but not everyone is--my issue is my dexterity, I just don't trust myself with wires.  to just switch to a regular 3 prong  is a simple swap out, GFCI is more involved.




there are adapters, but I would not use an adapter with an AC.

and yeah, if there has never been an AC there, you will have to see what else is on the circuit...any individual outlet should be able to support an AC, BUT if there is anything else on the circuit, that can over load it.  I used to have an AC on a shared circuit...i could not run anything other than a light or clock at the same time...

I don't think there is anything else, aside from maybe a light, on this circuit.

I was planning on doing this myself, until i got scared by reading some of the comments here oh oh

From what I've been reading/watching re: DIY of this, it does seem pretty straightforward, unless I'm missing something.

As for hiring a handyman VS electrician, if a dedicated circuit is needed or is the "preferred" way to do this, then a handyman probably isn't the best choice, right? Since they're not a licensed electrician.



yeah, if you want to do something with a circuit, you probably need an electrician..a permit might be needed for that...and i heard in NJ a homeowner can do their own electric..but if you hire someone they must be licensed.


and a circuit would be more work, maybe enough for an electrician to be interested....it may just be very hard to find an electrician willing to come just to spend 3 minutes changing an outlet.


a NJ homeowner can do anything on their house, but permits and inspections are still required.  You can't work on a multi-family if you live in half.  This of course doesn't apply to this situation.  Nobody pulls a permit to change an outlet.  



FilmCarp said:

a NJ homeowner can do anything on their house, but permits and inspections are still required.  You can't work on a multi-family if you live in half.  This of course doesn't apply to this situation.  Nobody pulls a permit to change an outlet.  

as i referenced...a permit might be needed for a circuit..not needed to replace an outlet


Most older homes in this area were not wired for the loads they sustain today and require additional wiring to sustain today's appliances.  For instance, my home was originally wired with only four circuits.  If you intend to put in a 12K BTU AC, I suggest you identify the circuit you intend to put it on, and then turn the circuit off so you can see which other lights and outlets are connected.  That will give you an idea of what the load on that circuit could possibly be.  That said, 12K is a very heavy draw for a 110 volt system.  I  myself would feel more at ease having a new dedicated circuit installed for this usage.


As far as I understand, GFCI will indeed work without a ground wire. However, any GFCI will only work if you are grounded somehow. If you are not grounded, you are toast!


Coming in a little late to the party, but a couple of comments.    There's some good info above as well as a few things that make me cringe.  I'm not an electrician (an engineer by training) but I did work for one during a summer in college, and he showed me a lot of scary things.  Nowadays, I work a lot on DC electrical systems (i.e. not houses), but I have done a ton of troubleshooting in my 1925 Maplewood house. 

In your case, let's start "bottom to top".  

A 12,000 BTU AC unit will draw about 10A +/-1A when operated at high settings (fan, compressor).   So, a 10A circuit at the box would be inadequate for this load, especially if there is anything else on the circuit. Even a 100W bulb would add a bit less than 1A draw, which would likely trip the circuit.  

As far as the wires themselves,  most older Maplewood houses have some form of BX (Technically AC - Armored Cable).  But, there are many flavors, including some with a separate grounding wire, grounding strip.  Etc.  If you pull the outlet cover and can see into the box, you should be able to tell.   Ideally, it's BX with a separate ground wire or strip.   Also, there are different wire gauges within the bundle.  Most likely you have 14/2 (14 gauge 2 wire).    The maximum "ampacity" for this is typically 15A, so you are probably okay, assuming the wire is in good shape.  Nicks, strain from over-bending or repeated twisting increase resistance (decrease capacity).  Increased resistance = heating = fire risk.    But starting with decent BX is at least a plus.  If you have any doubts, the safe bet would be to run a new circuit as described elsewhere.  

As far as grounding,   there are so many potential issues it's hard to pick a place to start.  In most houses I've worked on with BX,  the old metal outlet boxes are reasonably well connected to the cable sheathing (which is not to current code as mentioned).   In a few cases, they actually have a separate ground wire in the bundle.   If other 3 prong outlets in the house show a good ground (using the testers mentioned above),  then you can assume that there is SOME level of grounding in the system.   All the cautions mentioned apply.    Adding a GFCI would then help, especially if there are any other faults in the wiring and also because window ACs can actually generate standing water (condensate or incorrect pitch resulting in water intrusion). The one thing I would absolutely stay away from is one of those cheap, gray plastic "adapters".   Their only job is to defeat the safety of the third prong (Their ground strip fails easily under any twisting load).   

Dunno if that makes things clearer or not, but it makes me feel better grin



catch22 said:

Coming in a little late to the party, but a couple of comments.    There's some good info above as well as a few things that make me cringe.  I'm not an electrician (an engineer by training) but I did work for one during a summer in college, and he showed me a lot of scary things.  Nowadays, I work a lot on DC electrical systems (i.e. not houses), but I have done a ton of troubleshooting in my 1925 Maplewood house. 

In your case, let's start "bottom to top".  


A 12,000 BTU AC unit will draw about 10A +/-1A when operated at high settings (fan, compressor).   So, a 10A circuit at the box would be inadequate for this load, especially if there is anything else on the circuit. Even a 100W bulb would add a bit less than 1A draw, which would likely trip the circuit.  

As far as the wires themselves,  most older Maplewood houses have some form of BX (Technically AC - Armored Cable).  But, there are many flavors, including some with a separate grounding wire, grounding strip.  Etc.  If you pull the outlet cover and can see into the box, you should be able to tell.   Ideally, it's BX with a separate ground wire or strip.   Also, there are different wire gauges within the bundle.  Most likely you have 14/2 (14 gauge 2 wire).    The maximum "ampacity" for this is typically 15A, so you are probably okay, assuming the wire is in good shape.  Nicks, strain from over-bending or repeated twisting increase resistance (decrease capacity).  Increased resistance = heating = fire risk.    But starting with decent BX is at least a plus.  If you have any doubts, the safe bet would be to run a new circuit as described elsewhere.  

As far as grounding,   there are so many potential issues it's hard to pick a place to start.  In most houses I've worked on with BX,  the old metal outlet boxes are reasonably well connected to the cable sheathing (which is not to current code as mentioned).   In a few cases, they actually have a separate ground wire in the bundle.   If other 3 prong outlets in the house show a good ground (using the testers mentioned above),  then you can assume that there is SOME level of grounding in the system.   All the cautions mentioned apply.    Adding a GFCI would then help, especially if there are any other faults in the wiring and also because window ACs can actually generate standing water (condensate or incorrect pitch resulting in water intrusion). The one thing I would absolutely stay away from is one of those cheap, gray plastic "adapters".   Their only job is to defeat the safety of the third prong (Their ground strip fails easily under any twisting load).   

Dunno if that makes things clearer or not, but it makes me feel better grin

great information, thank you!



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