Upgrading Two Prong Slotted Receptacles?
90% of my house has two prong slotted receptacles, most are BX cable and therefore are grounded – if I understand correctly. What options do I have for changing all the outlets to 3-prong grounded? Is my only choice to pull all new cable to each box? I live in ranch so working from the attic and basement is viable, but its the horizontal runs of cable in the wall that concern me — do you just disconnect the old and leave in the wall, or do you have to open up the walls?
I’d love to hear from anyone with experience on this that can suggest a good game plan. I am obviously not an electrician but have a good working knowledge of basic home wiring, this would be my first stab at this type of project though — its my first house so money is tight, but if hiring an electrician is clearly the way to go then I’ll just need to face the facts.
Thanks
Replies
First off you should get an electrician in to examine your wiring. Make sure you get a reputable one though because he might take one look and say "all you wiring is bad, I'M going to have to replace it". If it passes the test its time for another. Put a tester between your hot wire and the metal box if it reads at least 105 volts your good. Make sure you know what your doing though, electrical is nothing to be messed with.
Ummm, don't count on that BX being a great ground... if it's grounded at all.
You should first of all confirm your electrical service actually has a real modern ground. My 1960 ranch was just bonded to a cold water pipe in the slab... maybe it was actually a working ground - I'm glad I never had to find out.
I recently replaced my 100 amp service panel with a 200 amp panel... not that I need 200 amps, I was running the house on 40 amps while I was cutting it over! I replaced it because I needed more circuit space and my old panel was missing the cover. Breakers in the rain, hooray!
Here is something to keep in mind, the hot and neutral wires are the only ones carrying current - UNLESS SOMETHING GOES HORRIBLY WRONG! That would most likely be your power strip eating up a power surge and feeding it through to the ground. Another possibility is getting zapped in the bathroom. The thing that is important is that ground wire normally does nothing, and hopefully will never ever do anything!
With that in mind, there is a recognized way of providing a real ground for your outlets that your will replace with modern 3 prong style. You can get a spool of 12ga. wire (Not sure if it needs to be insulated or not, but they make it in green if you need it!), and string it between your walls - through the floor or through the attic - to each outlet. Make the proper connections in the box (do a search on wire nuts, there was a great post on them awhile back) and to the outlet(s). Feed all these wires back to the main breaker panel - NOT A SUBPANEL. You will connect these wires to the empty spots on the neutral/ground bar.
You of course need to make sure that Neutral/Ground bar is actually grounded.
Rebuilding my home in Cypress, CA
Also a CRX fanatic!
Don't know if you saw this post - care to comment on what I said?Rebuilding my home in Cypress, CA
Also a CRX fanatic!
thanks for the replies. Paul, I was actually planning on upgrading my service from 100 to 200 also. I have a Federal Pacific panel which I know everyone recommends replacing. I think my best bet is to get an electrician in to review the wiring system for the house, do the panel upgrade and bid on any other upgrades that truly need to be done. Once I know exactly where I stand then I'll feel more comfortable working on the other wiring projects that are on the horizon (new kitchen, bathroom, etc...)I was thinking of just pulling new grounds for all the receptacles like you suggested, but the more I think about it -- with all the projects lined up for renovating this house, I may just bite the financial bullet and get the pro in for all the electrical work. I have to realize that my time is also money, and when I think about the amount of time I would put into the electrical work I'm sure I can justify paying someone else to do it.thanks!
Just in an effort to save you time, effort and money, you might want to consider exactly which outlets actually need a ground. For instance, power strips and computers -- anything with a three prong plug -- needs a ground.
But a living room outlet with only a table lamp and a clock radio plugged into it, doesn't. Most tools nowadays are double insulated.
~Peter, a fierce opponent to AFCIs
thats a good point Peter -- I do have a tendancy to overdue things. I want to replace all the painted over receptacles and thought it would be nice to get the whole place updated. Maybe I can live with getting the new service panel and running grounded circuits where I know I'm going to need them (computer, TV, etc...)I'm always thinking re-sale value, but I'm pretty sure I wouldn't get back the cost of upgrading all the wiring. At the very least, I think its something that I can push off for a while as long as any of the sensitive electronics are covered.Thanks
Refigerator, freezes, sub-pumps and surge protectors (computers, high end TV's) should have a true EGC connected to a grounding receptacel. As I set in my post to Paul the AC cable (so called BX) does qualify for use as an EGC if it was properly installed.Other places a GFCI can be used.The first 3 should not be on a GFCI because of the potential damages from false tripping of the GFCI.The surge protector because it needs the EGC for maximum protection of the equipment..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
You are mixing up equipment grounding conductors (EGC) with the ground electrode system. That is commonly done and I don't understand all of the exact details.The EGC is what is connected to the ground terminal on the receptacle.INSIDE the house the important thing is that all metallic equipment be bonded together.That include the EGC being connected to the ground bus is bonded to the water pipes. It does not matter if the water pipe is metallic outside the house or not.The sink faucet and the refigerator which is plugged into a grounded receptacle are all at the same potential, the "ground".The main purpose of a ground electrode system is to sink surges from any near by transient (lighting). "Ummm, don't count on that BX being a great ground... if it's grounded at all."From the NEC"320.108 Equipment Grounding
Type AC cable shall provide an adequate path for equipment grounding as required by
250.4(A)(5) or 250.4(B)(4).""250.4(A)(5) Effective Ground-Fault Current Path Electrical equipment and wiring and other
electrically conductive material likely to become energized shall be installed in a manner
that creates a permanent, low-impedance circuit facilitating the operation of the
overcurrent device or ground detector for high-impedance grounded systems. It shall be
capable of safely carrying the maximum ground-fault current likely to be imposed on it
from any point on the wiring system where a ground fault may occur to the electrical
supply source. The earth shall not be considered as an effective ground-fault current path.""You can get a spool of 12ga. wire (Not sure if it needs to be insulated or not, but they make it in green if you need it!), and string it between your walls - through the floor or through the attic - to each outlet. Make the proper connections in the box (do a search on wire nuts, there was a great post on them awhile back) and to the outlet(s). Feed all these wires back to the main breaker panel - NOT A SUBPANEL. You will connect these wires to the empty spots on the neutral/ground bar."It can go back to a properly wired sub-panel.It can go to any box that has a approperly wired EGC in it.IN addition a GFCI can be installed and the ground left unconnected. But it needs to be labeled as not ahving an ground. Individal packages of GFCI's usualy include the label..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
yeah, I thought the BX sheathing was grounded as well...So, can't he just run a green jumper from a ground screw in the box to each device?
Yes, but most older boxes don't have place for a grounding screw.You would need to drill and tap the box (8-32 IIRC) for the ground screw.There is also a clip that will slip over the edge of a box and hold a wire. I understand that they are not approved (UL listed) but I have never tried to research it..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
The common green ground screws in the store are 10-32. But I have seen other sizes included with light fixtures!Frank DuVal You can never make something foolproof because fools are so ingenious.
"The common green ground screws in the store are 10-32. But I have seen other sizes included with light fixtures!"Thanks.Do you know if the metal grounding clips are approved (UL listed) or not.I heard someplace that they wheren't. But I have not had need to use any so I have not tried to find out..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
wow - what great contributions, The number one thing I learned from this thread is......hire a pro! At least get one in so that he can get me to a level playing field by inspecting the existing system - I have just moved into this house so who knows what kind of electrical work was done prior (although on the surface it doesn't look as scary as some other places I've seen - my childhood home for one)I hope people keep contributing to this thread -- it seams like the whole grounding issue has a lot of grey area to it.
alright, I did some digging around in the wiring tonight -- there are some newer NM cables with ground wires in the house - in each of the j-boxes the grounding wires are not twisted together with wire nuts, but are looped around the coverplate screw. Any thoughts on this? Does this provide a sufficient ground? I have checked all of the 3-prong outlets in the house with a plug-in tester and they read that they were wired correctly and grounded -- I know these testers don't measure the quality of the ground though.I traced the one circuit I want to tap into back to the panel and it is grounded to the ground bus bar. Should I take all the grounds in the j-box - including the new cable I am running - and twist them together with a wire nut?
If you can manage to get the grounds together, it would be wise to twist then together with a wire nut. I like the special green ones that allow one wire to stick through as a pigtail.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
"Should I take all the grounds in the j-box - including the new cable I am running - and twist them together with a wire nut?"
Short answer -- yes. Also, if the box is metal, you need to get it grounded as well. The green wire nuts with a hole in the top ("Greenies") are nice for this when wiring new, 'cause you can leave one ground wire long to poke out the top and screw to the box. If you are just connecting existing wires, they may not be long enough for this. In that case, just use a properly-sized nut and add a pigtail to the group. Then ground that to the box. The green grounding screws are preferred if your box has a threaded hole for one, but sometimes installers use the cable clamp screw or, as they did in your case, the cover screw. I wouldn't do that since it makes it a pain to deal with the clamp or cover later and is kind of "iffy" as far as a good connection goes. In old work, I prefer to use the green clips. Don't know if they are code, and can be a bit tough to install sometimes, but they are way better than using the cable clamp or cover screws.
Mike HennessyPittsburgh, PA
AS I understand it, the object is to maintain the ground throughout the circuit, if you happen to be working on some part of it. So attaching the ground to the cover screw is not ok. When you take the cover plate off, the ground might not be continuous anymore.Of course, this is with metal boxes. Plastic ones don't need to be bonded to the ground.And yes, bind the grounds together with a wire nut.
I thought the green grounding clips were approved. They are a life saver when mounting surface metal boxes. But maybe it is a jurisdictional thing, rather than UL.
After hearing about badly wired subpanels in other posts, especially ones in older homes, and where real true grounding is in question, I would think that it would be safer to take it back to the source. Of course you can daisychain off the closest grounded connection.
Having an actual ground connection I think is the starting point in this whole escapade. If you looked at my old service panel, you would have seen a 6ga. wire feeding out the bottom. I would have thought that would have connected to a rod or uffer. Nope, just the cold water pipe. one of my neighbors with the same house as mine has his panel in a slightly different location... a few feet from it is a thick cable comingout the bottom of the house - and neatly sliced off. I think they just cut the cable when they poured new concrete aroud the house.
Is there any easy way to see if something that should be a ground actually is?Rebuilding my home in Cypress, CA
Also a CRX fanatic!
A metallic water pipe is an excellent ground electrode and you MUST USE ONE if you have it.It used to be the main or only ground electrode. But that is no longer allowed as the only ground electrode because it can be replaced by plastic some time in the future.There is equipment to measure the resistance of the ground electrodes. But it is specialized and many electrican won't have one..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
You can test for ground with any continuity tester, as long as you have a known ground. If nothing else, run a wire to a ground rod and drag it around with you.David Shapiro had an article in FHB years back, where he explains one way to go. I think it amounted to verify one ground, plug in a 3 prong extension cord and drag it around with you.
Yep, that's the key - proving that your system IS grounded.Rebuilding my home in Cypress, CA
Also a CRX fanatic!
I think you are missing the point. It isn't that knowing the system is grounded, it is having access to any known ground to test the system.David's article goes into how to test first for a known ground, and then test whatever you want.
This thread has provided plenty of examples of why evaluating a ground ought to be left to a pro. I really have not seen such a collection of misunderstood or misapplied knowledge since the last "Global Warming" conference. Not that I doubt anyone's sincerity; it's just a lack of knowledge. Don't feel bad, though ... a lot of sparkies are weak on the details. (They are taught the 'right' way of doing things, and aren't so well versed on all the "wrong" methods out there). So, a summary is in order.... The first point: in an old home, where all sorts of folks have tried to "improve" things ... all bets are off. One sure clue is the mixing of different wiring methods and generations .... for example, yellow Romex in a house with a fuse panel. This sort of thing is a warning to look at things real close. The little plug-in testers are a fine starting point, but are not perfect. They can be fooled, and they do not measure "quality." Nor does a continuity tester.
You see, a ground path has to be able to clear a fault; that is, carry maybe 90 amps for a split second, so that breaker will trip. That much current can be "choked" by different flaws in the ground path. Without getting into heavy theory, this is one of the differences between AC and DC current, or between 'impedance' and resistance. If the ground path will carry only, say, 30 amps, it will take a lot longer for that breaker to trip. Suffice it to say that a lot of trade practices, that have not made it into the code (some have recently entered the code) are there to ensure a low-impedance ground path. For example, attaching the ground wire firmly to the box by itself, rather than 'sharing' a cover plate screw. Or using a pigtail, even with a metal box. Or running a ground wire in the bx (flex). Now: What is grounding for? First, you need to ask the right question.
There are two "types" of grounding, and both are for very different reasons.
One is for lightning, and to stabilize the voltage: That's what the ground rod is for. Older homes used the water supply pipe for this purpose, but that is no longer done. Completely different is grounding for safety ... a way to make 'lost' current find it's way easily back to the panel, so a breaker will trip. That's what the ground wire is for. It's also why the water heater pipes are 'grounded.' (Just in case the element cracks). In the mid-60's, another method of dealing with 'lost' current was developed: the GFCI. These work by shutting things down if any current 'leaks.' From a safety standpoint, the GFI is probably a better approach. Modern homes use both- grounding everywhere, and GFCI as well in 'higher risk' areas. That convenient ground path is also used for some other purposes. The NEC bans "objectionable" current on the ground path- a 'loophole' that manufacturers have taken full advantage of.
Many electronic things let a tiny amount of current into the ground, especially when the appliance is "off." Timers, photocells, motion sensors, fluorescent ballasts are all examples that might do this.
Many power supplies and surge suppressors also use the ground path to "dump" excess electricity. "Ground path" means a good path back to the panel ... it has nothing to do with the dirt under the house! I hope I've cleared thing up a wee bit.
> Many electronic things let a tiny amount of current into the ground, especially when the appliance is "off." Timers, photocells, motion sensors, fluorescent ballasts are all examples that might do this.You have some examples of this?> Many power supplies and surge suppressors also use the ground path to "dump" excess electricity.Can you show me a power supply that does this, other than due to an imbedded surge suppressor on the input wires?
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
Dan, I have an Intermatic timer, that is installed in the place of a light switch, that requires the ground in order to operate. In a similar manner, Some Leviton motion-sensing light switches, and Lutron dimmers, fit in this category. The instructions will stress that a good ground is required in order for them to operate. Yes, "power supply" is a broad term. Many do incorporate some sort of surge protection; others have electronic components that require a ground in order to operate. Bill, I did not want to get into discussing the semantics of the NEC. The section on grounding, in particular, is poorly worded; just note the massive revisions in the past few cycles. The whole "grounding vs. bonding" argument is beyond the scope of this forum. Yes, the NEC does refer to the water pipe as a GEC ... still ... yet the wire used for this is quite a bit smaller than the one to the ground rod / ufer / whatever. This suggests to me that we are only 'bonding' that pipe, and not really using it as a grounding electrode. At this point, we're splitting hairs. I thought it more important that folks understand that the third prong of their receptacles has nothing to do with Mother Earth, and everything to do with getting back to the panel.
The grounds in these cases aren't carrying "leakage" from the units, but rather are providing a ground reference for electromagnetic shielding. The only time current is "shunted" to ground is when an interference filter or surge suppressor shunts noise or surges.To say that a section of the NEC is poorly worded is like saying Saddam Hussein has neck problems.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
BIG GRIN to that...I always wonder if that's just a function of it's being written by committee, or it's a way to convince us we always need to pay big $$ to an electrician to chane an outlet?
" Older homes used the water supply pipe for this purpose, but that is no longer done."Actually the code says that, if it qualifies, the cold water supply pipe MUST be used as a ground electrode.But if used it can not be the only one..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Great post - glad to have some help in clearing up some common misconceptions here.
FWIW, I have seen a lot of issues with grounding of armored cable. It "should" be a good ground, and in new installs NEC says it "must" be a good ground, but in practice in older homes, it often is not a good ground. We have investigated a bit and come to the conclusion that there are several causes for this, ranging from poor connections between the "armor" and the box, ground etc., but have also found tha the "armor" itself often does not have adequate ground continuity.
There are several different issues floating around here, and they can get confused.First, it's far better to have the ground connection from a grounded outlet run to the ground bus in the breaker panel than to have it run to some other presumed ground (such as a pipe or ground rod). This is because, so long as the neutral from house to pole is solidly connected, the ground bus (or neutral bus, if no ground bus) can take about as much current as the panel's main breaker can supply. A separate ground rod, on the other hand, may not be able to handle more than about five amps, even if it's reasonably "good", and you're often not sure whether a water pipe is "ground" at all.The "bonding" of electrical ground to a grounding electrode system in the house serves several purposes:1) Combined with the grounding electrode for the pole transformer and the grounding electrodes in all the other houses nearby, an excellent and reliable ground is established for the system as a whole. Your grounding electrode system is supplying its "fair share" of this effort.2) Should the neutral wire from the POCO somehow get disconnected, the local grounding electrode system helps assure that the house's electrical ground will not "float" to a dangerous level.3) Should a live wire come in contact with something like a metal water pipe inside the house, the "bonding" of all the large metal objects together helps assure that the voltage will be shunted to ground, vs making the pipe (and possibly plumbing fixtures) "live".4) The grounding electrode system provides a "low impedance" path to ground for lightning-induced surges.Note that of the above purposes, only #2 is even partly related to the wiring of grounded outlets.With regard to testing grounds, it should be noted that just because a metalic object shows "continuity" to ground does not mean it's a good and reliable ground. The connection may be "made" by a whisp of wire or flake of metal that will vaporize when presented with a 50-amp short-circuit surge. Or there may simply be too much resistance in the path, such that full voltage applied to the presumed ground will result in only a few amps of current -- not enough to trip a breaker.When in doubt, use a GFCI. Other than the false trip hazard with fridges/freezers, etc, there's no harm in using one in cases where the ground "ought" to be good but is suspect (eg, corroded BX connections).
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
For god's sake don't do what a co-workers hubby did...he ran a jumper from the ground screw on the recep, to the neutral. According to his "little tester" it said the outlet was grounded, so he says "I saved a $$$$ by not having an electrican doing i properly."
I quit wasting my breath trying to explain the "wrongness" of his actions. When they sold their house, I wanted to stop by and tell the new owners what was going on...I was kind of surprised the inspector didn't catch it..but that's another story....
Rip