Commercial HVAC equipment grounding

[george nicholson]

I have several 3 phase roof top package HVAC units that require #10 THHN. The conductors are pulled in EMT to a 1900 box under the roof deck. Then go thru roof in non-metallic flex to the disconnect mounted on the unit.

Can we connect a green #12 at the 1900 box using a green pigtail and pressure connector to accomplish the grounding to the disconnect? The EMT is continuous to the load center.

 

[480sparky]

If the ungrounded conductors are #10, you need a #10 ground.

 

[george nicholson]

addition question on ground

addition question on ground

If we have 3 phase units units requiring #8, or #6 ccc's and the entire system is piped with EMT from load center to hvac disconnect no ground is required is that correct?

So if a piece of non-metalic flex is added between the EMT and disconnect then do we have to pull a ground from panel all the way to the disconnect?

 

[480sparky]

If we have 3 phase units units requiring #8, or #6 ccc's and the entire system is piped with EMT from load center to hvac disconnect no ground is required is that correct?

If it's EMT all the way, then no ground conductor is required. 250.118(4).

So if a piece of non-metalic flex is added between the EMT and disconnect then do we have to pull a ground from panel all the way to the disconnect?

Not necessarily need to pull all the way back to the panel, but between the boxes/pull points on each side of the non-metalic flex. You must maintain continuity of the ground.

 

[george nicholson]

So if the ccc is #6 could you use #10 between each end of the flex? Screw connect to the j-box at start of flex and terminate under the disconnect's lug?

 

[Dennis Alwon]

So if the ccc is #6 could you use #10 between each end of the flex? Screw connect to the j-box at start of flex and terminate under the disconnect's lug?

That would depend on whether the #6 is used at it's needed ampacity or whether it was upsized for voltage drop. Art. 250. 122 will tell you what size your egc will have to be based on the breaker size. Read art. 250.122(B)

 

[480sparky]

So if the ccc is #6 could you use #10 between each end of the flex? Screw connect to the j-box at start of flex and terminate under the disconnect's lug?

Yes.

 

[george nicholson]

#6 is used at its ampacity. The inspector is trying to say that the ground always has to go to the panel if there is anything but solid EMT all the way.

I hate to argue but we have about 15 units total and it will be a pain to re-do all the way to the panel.

 

[480sparky]

EMT is an acceptable grounding conductor.

250.118(4). Also, read the last sentence of 250.118

"... or a combination of the following:"

Is this an AHJ inspector, or possibly someone representing the EE/owner/other trying to make sure the specs are followed?

 

[Dennis Alwon]

I hate to argue but we have about 15 units total and it will be a pain to re-do all the way to the panel.

Don't argue with him just show him the code sections. Now if the specs call for an egc all the way back then you need one but the NEC does not require a separate conductor if the raceway is EMT.

 

[LarryFine]

The inspector is trying to say that the ground always has to go to the panel if there is anything but solid EMT all the way.

He is incorrect, NEC-wise.

 

[george nicholson]

There is no EE this is AHJ only. Not arguing already faxed code and spoke on phone.

What happened is a new employee ran #8 black from the panel to the disconnects and taped it green on each end.

I suggested to the inspector that we simply jump from j-box to disconnect with green #10 which is actually size required and abandon the black #8 totally. He wants #8 green from panel to the disconnect and is not moving on it. I have already faxed the code to him. I am going to the AHJ chief Monday, just wanted to confirm that I was not missing something.

 

[480sparky]

There is no EE this is AHJ only. Not arguing already faxed code and spoke on phone.

What happened is a new employee ran #8 black from the panel to the disconnects and taped it green on each end.

I suggested to the inspector that we simply jump from j-box to disconnect with green #10 which is actually size required and abandon the black #8 totally. He wants #8 green from panel to the disconnect and is not moving on it. I have already faxed the code to him. I am going to the AHJ chief Monday, just wanted to confirm that I was not missing something.

If you're reidentifying #8, that's not allowed per 250.119. Key word is continuous. Maybe that's the inspectors' beef.

 

[infinity]

If you're reidentifying #8, that's not allowed per 250.119. Key word is continuous. Maybe that's the inspectors' beef.

What do you mean by continuous?

 

[M. D.]

It seems to me the inspector is willing to over look the tape on a #8 for what he believes is a better EGC ... He is wrong

What is so hard to understand about this

250.118 Types of Equipment Grounding Conductors.
The equipment grounding conductor run with or enclosing the circuit conductors shall be one or more or a combination of the following:

your run could include all of these as as the equipment grounding conductor.

• Conductor. A bare or insulated conductor [250.118(1)]
• Rigid Metal Conduit [250.118(2)]
• Intermediate Metal Conduit [250.118(3)]
• Electrical Metallic Tubing [250.118(4)]
• Listed Flexible Metal Conduit as limited by 250.118(5)
• Listed Liquidtight Flexible Metal Conduit as limited by 250.118(6)
• Listed Liquidtight Flexible Tubing as limited by 250.118(7)
• Armor of Type AC Cable [250.118(8)]
• Copper metal sheath of Mineral Insulated Cable [250.118(9)]
• Metal Clad Cable as limited by 250.118(10) [250.118(10)]
• Metallic cable trays as limited by 250.118(11) and 392.7
• Cablebus framework as permitted in 370.3 [250.118(12)]
• Electrically continuous metal raceways listed for grounding [250.118(13)]
• Surface metal raceways listed for grounding [250.118(14)]

 

[Dennis Alwon]

I wish they would change that rule. Here he has a perfectly good ground from the panel to the unit and because it is taped the wrong color it is no good. That's ridiculous.

 

[M. D.]

What do you mean by continuous?

250119
Individually covered or insulated equipment grounding conductors shall have a continuous outer finish that is either green or green with one or more yellow stripes except as permitted in this section........

Larger than six we are permitted to identify the conductor,... and tape is one way to do it.

This guy will no doubt expect that emt to be painted green

 

[M. D.]

I wish they would change that rule. Here he has a perfectly good ground from the panel to the unit and because it is taped the wrong color it is no good. That's ridiculous.

This is not what I understand the issue to be,.. perhaps I misunderstood??

 

[Dennis Alwon]

This is not what I understand the issue to be,.. perhaps I misunderstood??

He said they ran a #8 back to the panel and taped it green. The inspector wants a green #10 all the way back.

What happened is a new employee ran #8 black from the panel to the disconnects and taped it green on each end.

 

[tryinghard]

There is no EE this is AHJ only. Not arguing already faxed code and spoke on phone...

The inspector really does have the burden of proof when stating a violation, you should be able to ask specifically what is the violation to avoid guessing.

I think this has already been said but in summary, acceptable equipment grounding conductors are listed in 250.118 and metallic conduit is one along with metallic flex. The EGC (if a physical conductor or bond) has to be upsized for voltage drop proportionally only if the phase conductors were upsized 250.122(B). The EGC is sized from the overcurrent protection device (breaker/fuses) per Table 250.122.