View Full Version : Subpanel Neutral & Ground On Same Bar?
06-18-2009, 09:21 AM
I just met with an electrician. I want to install a dedicated circuit in my sub panel. Since I live in an old multi-unit, the sub panel only has a neutral bar. I ask the electrician what are you going to do with the ground wire? The electrician replied, "Since the neutral bar is bonded, you can put the ground wire on the same bar with the neutral wire." The electrician said this was safe. Is this correct?
06-18-2009, 09:52 AM
Well there is "safe" and then there is "safer"!
Older electrical systems were basically safe. But newer electrical systems are safer.
The difference is if there is an electrical malfunction. Like if a wire comes loose. Or someone drills a hole in a wall and this causes a wire to break.
Newer electrical systems take this into account and are designed to be safe even if these malfunctions occur.
So basically safe? Yes so long as no wires become disconnected.
Could it be safer? Yes, a separate ground, non-bonded neutral bar, and separate ground wire run to the main panel would be safer.
06-18-2009, 10:15 AM
I have a diagram to better illustrate my setup.
Since I'm installing an mini-split ac, to be on the safer side,
can I just install a ground rod next to the condenser and ground the condenser. Would this make it safer?
06-18-2009, 12:31 PM
No! You can not use a ground rod.
06-18-2009, 07:05 PM
Is the panel fed with 3 wire cable or three wires in conduit?
If it's fed with conduit simply run the ground wire to the enclosure.
If it's fed with 3 wire cable you don't have any good choices. I'd still bond it to the enclosure.
I'm not sure where the NEC stands on this type of non compliant existing installation.
The only danger is if you somehow "lose" the neutral going back to the source. Then the current that should be flowing thru the neutral will try to take a path to ground thru the ground wire on the circuit you installed.
For example, if a refrigerator is plugged into that circuit, the metal frame would become energized and you may be the path to ground it is seeking.
A ground rod is not your solution.
06-19-2009, 07:19 AM
The best solution would be to run a ground wire from the main panel to the sub panel. But since this is a dedicated circuit to a AC condenser I wouldn't be terribly worried about wiring it as proposed. I would agree an addditional grounding rod is not the solution.
06-19-2009, 08:28 AM
The three wire feed to the sub panel is a 2" conduit.
I email City Building Dept and they were not very helpful,
"modern sub panel usually have separate bars."
From what I understand is, it's safe to put ground and neutral wire on the same bar. Installing a ground rod next to the condenser is no use. (This was suggested from a HVAC Installer by the way).
Installing a ground wire from main to sub panel is out of the question, first it's to far away and second will be to difficult.
I'm going to put them on the same bar and going to install a GFCI outlet and forget about the ground rod.
Any other suggestions welcome.
06-21-2009, 05:02 PM
The conduit will be your ground path.
Install a ground bar to the can or just attach the new ground wire to the can with a self tapping screw.
Do not put it on the neutral bus.
I repeat, do not put it on the neutral bus.
06-23-2009, 10:58 AM
Newer systems take into account that the neutral is a current carring circuit. The ground should not carry current unless there is a fault. From what I can tell is that unless you have a clear seperation from your service conductors of Neutral and ground, anything you do after that to seperate the two is pointless....