Installing new garbage disposal, Grounding questions

[effowe]

I'm getting a new disposal installed today and had a question about the grounding. When I took the plate off the old disposal, I only noticed 2 wires running through the conduit connecting it. Reading the instructions it says that a third wire should be connected for grounding. This is a permanently installed disposal, not one that is connected with a power cable. Here is the relevant section from the manual..

For all grounded, cord-connected disposers:
This disposer must be grounded to reduce the risk of electric shock in the event of a malfunction or breakdown. Grounding provides a path of least resist- ance for electric current. This disposer is equipped with a cord having an equip- ment-grounding conductor and a grounding plug. The plug must be plugged into an outlet that is properly installed and grounded in accordance with all local codes and ordinances.

For permanently connected disposers:

This disposer must be connected to a grounded, metal, permanent wiring sys- tem; or an equipment-grounding conductor must be run with the circuit con- ductors and connected to the equipment-grounding terminal or lead on the disposer.

I am thinking that the part in bold applies to me. Do I still need to get a grounding wire installed, or does the conduit itself ground the disposal?

 

[Linflas]

How old is the house? You sure it just wasn't cut off back where the outer insulation was removed? You definitely need to ground it.

 

[effowe]

How old is the house? You sure it just wasn't cut off back where the outer insulation was removed? You definitely need to ground it.

It's a new construction condo (built after 2000.) The conduit runs to a switched box which also connects the dishwasher. I'll get a picture.

 

[steppinthrax]

It's a new construction condo (built after 2000.) The conduit runs to a switched box which also connects the dishwasher. I'll get a picture.

It looks almost like a 3-way switch (does another switch control the disposal). Or that red wire is the ground. On the switch there should be a ground terminal, it is filled with a wire????? If not then someone mess up somewhere.. Another thing, i've never seen purple and gray wires WTF?

 

[effowe]

It looks almost like a 3-way switch (does another switch control the disposal). Or that red wire is the ground. On the switch there should be a ground terminal, it is filled with a wire????? If not then someone mess up somewhere.. Another thing, i've never seen purple and gray wires WTF?

The switch is directly connected to the panel, which leads me to believe that the red is in fact ground. Only the red and black are connected to the switch. The disposal is controlled by another switch by the sink.

 

[disappoint]

You need to hire a licensed electrician. The red wire is most certainly not ground. A ground wire is not connected to a switch. The ground wire is usually connected between the metal chassis of equipment and the ground bus bar of the electrical panel.

 

[effowe]

You need to hire a licensed electrician. The red wire is most certainly not ground. A ground wire is not connected to a switch. The ground wire is usually connected between the metal chassis of equipment and the ground bus bar of the electrical panel.

So that would be two hots coming in (red and orange) and one neutral (white)?

 

[disappoint]

So that would be two hots coming in (red and orange) and one neutral (white)?

The hot coming into the switch is black, when the switch is closed the red wire gets connected to the hot black wire. Yes white should be neutral. The orange wire is connected to the purple wire. Where those wires are going and what they are connected to is not shown in the picture.

So generally speaking:
white is usually neutral
black is usually hot
red is usually switched hot
green or bare copper is usually ground.

As for what the purple and orange wires are for you will have to see what they are connected to at the other end.

 

[effowe]

The hot coming into the switch is black, when the switch is closed the red wire gets connected to the hot black wire. Yes white should be neutral. The orange wire is connected to the purple wire. Where those wires are going and what they are connected to is not shown in the picture.

So generally speaking:
white is usually neutral
black is usually hot
red is usually switched hot
green or bare copper is usually ground.

As for what the purple and orange wires are for you will have to see what they are connected to at the other end.

Orange / Purple go to the disposal, Red / Black go to the dishwasher. On a hunch I decided to see if the conduit was connected to the ground on the outlet that's next to the disposal switch by the sink. I got my multimeter and put it in the ground (circuit off) and touched the conduit and I got continuity. I think they grounded the box in the wall with that outlet instead of running another wire. Whether or not that's to code, I don't know.

 

[DrPizza]

The metal conduit acts as the ground. With metal conduit, you can only use metal boxes.

So, yes to the very last question in the OP.

 

[disappoint]

Orange / Purple go to the disposal, Red / Black go to the dishwasher. On a hunch I decided to see if the conduit was connected to the ground on the outlet that's next to the disposal switch by the sink. I got my multimeter and put it in the ground (circuit off) and touched the conduit and I got continuity. I think they grounded the box in the wall with that outlet instead of running another wire. Whether or not that's to code, I don't know.

Unfortunately all a continuity tester will tell you is that there is a connection, not if it's a sufficient connection. For example if it was connected together with a thin 40 gauge strand of wire it would still show continuity. That of course would not be to code because it will not handle the current that could flow through there which could result in a fire.

I personally wouldn't trust conduit as my only ground. Conduit is not as secure as a third ground conductor. The NEC requirement is only a minimum standard. Conduit can come apart causing a ground fault.

Speaking of NEC, this circuit should be connected to a GFCI circuit breaker.

 

[SphinxnihpS]

The metal conduit acts as the ground. With metal conduit, you can only use metal boxes.

So, yes to the very last question in the OP.

Indeed. I just wanted to add, DO NOT place any importance on the color of the wire coating. Test it yourself.

 

[SphinxnihpS]

I personally wouldn't trust conduit as my only ground. Conduit is not as secure as a third ground conductor.

Why not? That is how the system is designed. Do you think the metal can't handle the load in the event of a short? lol

I usually just use one of the pre-drilled and threaded holes in the back of the box and loop the ground around a green screw. Self-tapping grounding screws can be had by the hundreds for a couple bucks.

 

[steppinthrax]

You need to hire a licensed electrician. The red wire is most certainly not ground. A ground wire is not connected to a switch. The ground wire is usually connected between the metal chassis of equipment and the ground bus bar of the electrical panel.

It really dosen't matter what the electrician chooses to use. The red wire "could" be ground. If all he/she had was 14/3 and they wanted to run it to the panel and to the switch that tha's fine. However, it's probably not to code. Usually the ground is uninsulated for a reason. If any sparks or electrical activity happens in the wire it will "induct" the ground wire and trip the breaker.

 

[SphinxnihpS]

It looks almost like a 3-way switch (does another switch control the disposal). Or that red wire is the ground. On the switch there should be a ground terminal, it is filled with a wire????? If not then someone mess up somewhere.. Another thing, i've never seen purple and gray wires WTF?

That's just a regular two-way circuit, but the wiring layout is mostly hidden in the walls. It's just the most efficient way for electricians to run the circuits. If you were to take everything out of the house and lay it out so it's easy to see, you will see it's really just several simple circuits with only hot wires/neutral wires, and no real travelers.

 

[steppinthrax]

The metal conduit acts as the ground. With metal conduit, you can only use metal boxes.

So, yes to the very last question in the OP.

The metal condute acts as a ground, but you still need a ground wire running through the cable....

 

[effowe]

OK I'm just going to go ahead with the install. It's been working fine for years, I don't think we need to bring an electrician into the mix. Thanks for all the help everyone.

 

[disappoint]

Why not? That is how the system is designed. Do you think the metal can't handle the load in the event of a short? lol

I usually just use one of the pre-drilled and threaded holes in the back of the box and loop the ground around a green screw. Self-tapping grounding screws can be had by the hundreds for a couple bucks.

Though the NEC recognizes certain raceways such as rigid and Emt as an equipment ground, under certain conditions the effectiveness can be breached. It is always good practice to include a separate equipment ground with the raceway and to exceed the NEC requirement, which is a minimum safety requirement.

Having done that, the important thing is to effectively bond the box and raceway to the equipment grounding conductor by an approved means such as a bonding screw. This must be drilled and taped. (Self drilling screws won't do, nor will wires wrapped around screws supporting the box). If there is metal to metal contact such as a surface box (handy box) the code recognizes that as grounding the yoke when a washer is pulled. Situations involving raised covers require a bonding jumper. Any raceway relied upon as an equipment ground connected using reducing washers or concentric ko's must be bonded around using grounding bushings.

 

[SphinxnihpS]

The metal condute acts as a ground, but you still need a ground wire running through the cable....

No. All you need is the ground from each switch and outlets attached to the metal housing. The box in the basement is what is grounded. The gauge of the metal is fine for any load a house can throw at it in a short, and the impedance is low enough to conduct to the ground.

 

[SphinxnihpS]

Though the NEC recognizes certain raceways such as rigid and Emt as an equipment ground, under certain conditions the effectiveness can be breached. It is always good practice to include a separate equipment ground with the raceway and to exceed the NEC requirement, which is a minimum safety requirement.

Having done that, the important thing is to effectively bond the box and raceway to the equipment grounding conductor by an approved means such as a bonding screw. This must be drilled and taped. (Self drilling screws won't do, nor will wires wrapped around screws supporting the box). If there is metal to metal contact such as a surface box (handy box) the code recognizes that as grounding the yoke when a washer is pulled. Situations involving raised covers require a bonding jumper. Any raceway relied upon as an equipment ground connected using reducing washers or concentric ko's must be bonded around using grounding bushings.

Just a note. The minimum requirement is well beyond any normal circumstance. Over-safety is built in. The screws I referred to are self-tapping, not self-drilling. The holes pre-drilled into these boxes were specifically drilled or the screws I recommended.

If what you say is true, most homes are woefully undergrounded, but since there is not a rash of burning homes from this cause, I doubt what you're saying is very important. The vast majority of homes standing today are wired exactly like I describe.

 

[disappoint]

No one is questioning the gauge of conduit. It's just better practice to run a separate ground. It's not necessary and it's not required. It's just good practice to do so.

 

[SphinxnihpS]

No one is questioning the gauge of conduit. It's just better practice to run a separate ground. It's not necessary and it's not required. It's just good practice to do so.

I'll agree with that when cost is no concern, after that it's always going to be about weighing pros and cons. Code has no cons. Overcode has some additional cost/work.

To be fair, I ran separate 10 gauge ground to all my 240 woodworking equipment. At the same time I didn't get the three-phase stuff because of the insane cost of bringing that to the house. When you get to three-phase stuff, this grounding issue is a lot more important.

This place is Half-assed Central, so getting someone to do even the bare minimum is a chore.

 

[effowe]

The new disposal went in without a hitch. We were able to use the old mount that was installed in the drain, so all we had to do was replumb and rewire it. Took about 30 mins total. :thumbsup:

 

[Red Squirrel]

The BX wire should act as ground, but test it first, for all you know it could be going to another junction box somewhere (possibly hidden in a wall which is against code) and then turn into romex.

I know it's done, but as a safety check, take a volt meter and go from the BX (the spiral metal feeder) or box to a known hot wire and make sure you get a 120v reading. Also those are some interesting wire colors you got there, is this in Europe by chance, I hear they have different color schemes though from my quick google search it's not those colors.

 

[effowe]

The BX wire should act as ground, but test it first, for all you know it could be going to another junction box somewhere (possibly hidden in a wall which is against code) and then turn into romex.

I know it's done, but as a safety check, take a volt meter and go from the BX (the spiral metal feeder) or box to a known hot wire and make sure you get a 120v reading. Also those are some interesting wire colors you got there, is this in Europe by chance, I hear they have different color schemes though from my quick google search it's not those colors.

All the wires are tucked away at this point, I might test it if something doesn't sound right. No this isn't in Europe, it's in Chicago. I am assuming the contractor was being lazy / cutting corners picking those wire colors.