dcsimg

PDA

View Full Version : Main Service Panel Ground


smorono
May 14th, 2003, 04:42 AM
I am installing a new service panel, I have a ground rod/ground wire attached to the meter base. Three wires from the meter base (hot, hot, neutral) to the main service panel. I then connected a second ground wire attached to the water main to the main service panel. Neutral and ground are not connected at the main service panel. Is this correct?

A second question- I installed a 220 disconnect for a heat pump. I used 6/3 wire w/ground. There is no place on the disconnect to attached the bare ground wire, shoud I connect it to the case of the disconnect box?

Thanks

6pack
May 14th, 2003, 05:21 AM
You need (2) ground rods spaced 6' apart just below finished grade.(no splice)#6. Ground to water system must be within 5' of point where piping enters building.(no splice) Local ruling here requires a #4 bare if running exposed thru joist space. At main panel ground(aka-bare green) and neutral(aka-white) must be connected togther(on same lug bar). Panel must also be tied in with this, should be bonding screw connecting that neutral/ ground lug bar to panel. Your only allowed (1)white(aka-neutral) from general wiring under a screw in grounding bar and (3) ground(aka-green or bare). Need to add a ground lug bar if no place to connect your ground wires in Disconnect.

imported_joed
May 14th, 2003, 06:18 AM
I think the bond to the water pipe needs to go to the meter base where your ground rods are not to the panel where the ground and neutral are separate.
Either that or the ground and the water pipe bond should go to the panel not the meter base. Ground is usually installed at the first disconnect in the system. This could be a separate disconnect or the main panel where the first disconnect is located.

Anonymous
May 14th, 2003, 01:01 PM
So I should remove the ground from the meter base and install 2 ground rods (6' apart) and a ground on the water pipe and run all three to the main panel. All 3 go to the neutral bar and tie the neutral and ground bars together with the bonding screw in the main panel. Is this correct? Thanks

6pack
May 14th, 2003, 03:56 PM
Sorry did not notice you said ground conn to meter base. Both grounds must go to main disconnect, in your case Main Breaker panel. I do not know where your getting (3) from? you only need (2). The #6 bare running to ground rods must connect to both Rods(continuos) no splice. Use acorn ground clamp pass wire thru and connect to 2ND Rod, Tighten both(Hex Nut) Then connect in breaker panel to Neutral bar.(1 Wire) Then run your ground to water pipe within 5' of entrance to house and connect also to neutral bar.(2ND wire).OK The rest you mentioned Fine. GL

bsirvine
May 16th, 2003, 08:56 AM
I hope that I am not confusing things here and I could be wrong, but the way smorenno wrote it up in the initial post sounds correct to me. Any professionals out there?

If you have run out of space for grounds add another ground bus to the box, bond it to the box and to the first ground bus.

6pack
May 16th, 2003, 02:32 PM
besirvine, Again going on what is required by POWER CO, since PVC pipe bonding is not an issue here! Power Co does not want any grounding wire to enter meter socket or pedestal. Possibly Smorono should check with Power CO.(utility co) on what they require??

6pack
May 17th, 2003, 01:28 AM
Srvine and Morocco, sorry your right accord to NEC, only (1) rod required as suplement to water piping within 5' of entry. Also they can go to either meter or main panel as I see it now. Again though where I'm now located, no ground may enter meter sockets, must go to main panel,also 2 rods required. Local and Power CO overide of NEC.Morocco would need to know if any such overides are required at his local. Also rereading post, noticed last statement? Neutral and ground NOT connected at main panel?? Just before that you mentioned running ground from water piping to main panel ?? Typing error or did you issolate the two?? They must be as One in main panel.?? Maybe I'M reading you wrong here! Sorry hope did,nt goof yah up there morroco.But I'd check onlocal ruling.

Wgoodrich
May 18th, 2003, 04:32 PM
If you have a metal wate pipe entering the home that is in direct contact with the earth for at least 10' then you must use this metal water pipe connected within 5' of where it enters the home as your main grounding electrode. Here you must install for a 200 amp service a 4 awg copper grounding electrode conductor per 250.66 of the NEC from that water pipe unspliced to either the meter base or to the main service rated panel. [some local rules forbid connecting this grounding electrode conductor inside the meter base. This would be a local rule you need to verify by your local inspector and power company, this is not what the NEC says] The NEC says either land in the meter base or main service rated panel.

Then if a metal water pipe exists in contact with the earth as discribed above then you must use that as your primary grounding electrode. The that metal water pipe is required to have a supplemental grounding electrode such as a ground rod as a back up to that water pipe just in case that water pipe is changed to plastic in the future. That ground rod may be connected with a 6 awg copper grounding electrode conductor to the meter base or to the main service rated panel or to the metal water pip within 5' of where it enters that house. Then if the metal water pipe is changed to plastic the supplemental ground rod will take over.

There is no place in the NEC other than if with a metal water pipe ground that the NEC requires more than one ground rod with the exception that if this ground rod has be meg tested and megs less than 25 ohms to ground a second rod or second grounding electrode listed in 250.50 must be supplied. [again there are some areas that have a local ruling that two ground rods are required but that is only a local ruling not a rule of the NEC.]

In a main service rated panel the neutral and grounding bars are to be made electrically connected.

If you have a metal water pipe but plastic water line entering the house then the metal water pipes must be bonded to the grounding system of the house service and may be connected to the ground rod or to the grounding electrode conductor or to the meter base or to the grounding bar inside the main service rated panel. The purpose of this is if with metal water pipes not in direct contact with the earth then the metal water pipes are without a grounding connection to the equipment grounding system of the house. This would cause a shock hazard if a hot wire touched that non grounded metal water pipe if not connected to the house electrical grounding sytem. Then this water pipe would remain energized and the panel would not be able to sense it. If connected to the main grounding system of you service it would caust that shorted hot wire to trip a breaker and let you know there was a short.

It is not instended to have a fourth wire connected between the meter base and the main service rated panel because it would try to take over as paralleled with the neutral and that wire would be too smal to carry the neutral load of the whole house and you would not know you have a loose neutral service conductor.

Hope this helps

Wg

bsirvine
June 23rd, 2003, 11:40 AM
OK, I am finally moving on my project.

I noticed that there was a spare knockout on the bottom of my meter base for a 1/2" conduit entry, so I am using that to run my #4 AWG CU ground conductor. I knocked out the plug and installed a PVC male threaded connector inside the meter base. The female went outside. I used PVC cement to connect the 1/2" PVC down conduit to the connectors on the meter base. I have a 1/2" PVC elbow at the bottom of the conduit. The #4 AWG bare CU conductor then runs 9 feet horizontally to my first ground rod and then 7 feet to my second. I am planning to use CAD weld connectors to attach the ground conductor to the 2 rods. Inside the meter base I am connecting the ground conductor to the load side neutral lug (bottom of the meter (center)). This way I won't be doing the "parallel" thing.

I did have one problem and I don't know how serious it is. I could not bury the horizontal run of the ground conductor to the required depth because of all the roots. It is probably like a minimum of 4 inches with a maximum of 6 inches deep. Is this a serious problem?

Inside the house the panel ground bus is grounded (or bonded) to the water pipes.

Wgoodrich
June 23rd, 2003, 08:32 PM
Sounds like you have a plan as long as you do not have a metal water pipe in direct contact with the earth for at least 10 feet.

Per the NEC 4 awg wire is only required to be protected if subject to severe physical damage. Just under the sod the short distance from the house to the rod should be fine.

Good Luck

Wg

bsirvine
June 24th, 2003, 09:14 AM
Thanks. I was not looking forward to having to cut those roots.

I don't know if I have 10 feet of metal water pipe buried outside my house (it might be plastic for all I know). The previous ground conductor is attached to the water pipe both above and below the water meter (within 5 feet of where it enters the house). I am not disconnecting it. Right now it goes direct to the ground businside the panel. With the two ground rods outside serving as primary ground this old ground left as it is serves as a bond to the cold water plumbing, correct?

Now I just have to bond over between the Input & Output of my hot water heater and to the gas piping (None of this has been done before).

jellis47
June 24th, 2003, 08:30 PM
as for you 2nd part to your ? a heat pump doesn't require a netural so you only need to run a 6/2 cable to the disconnect then from the disconnect to the heat pump. connect the ground conductor to the lug that is bonded to the disconnect it should have a ground symbol next to it.