Grounding, EGC;'s from appliances

[Dennis Franklin]

Hi, thanks for the priviledge of being able to communicate with someone on NEC/grounding issues. The Question I need help on is: When an appliance, such as a water heater, gas fired with minimal exposed metal water piping, is grounded, does the grounding conductor need to be DIRECTLY attached to the main distribution panel in a building, and sized in accordance with 250-66, using the main service feeders to the service panel for sizing the grounding conductor? (In this case, No. 4)And, when an appliance, such as an electric water heater, fed from a 100 amp sub panel, with a 40 amp,240 volt circuit, require DIRECT bonding to the Main Panel in the building, and sized in accordance with the service conductors of the main panel, in this case 4/0 feeders instead of the No. 4 feeders that feed the sub panel, which is fed from the main panel, and bonded back to that main panel with a No. 6 ground conductor???

 

[George Stolz]

Re: Grounding, EGC;'s from appliances

Dennis, welcome to the forum.

There are different principles at work in your questions. Let's separate them.
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• <font size="2" face="Verdana, Helvetica, sans-serif">Bonding a gas appliance (gas water heater)</font>
• <font size="2" face="Verdana, Helvetica, sans-serif">Bonding metallic water piping systems</font>
• <font size="2" face="Verdana, Helvetica, sans-serif">Bonding metallic components of a non-metallic water system</font>

<font size="2" face="Verdana, Helvetica, sans-serif">
The first & third items aren't required. If there is no electricity brought to a gas water heater, then you don't need to bond it. If there is an electric flue fan or something along those lines, then the fan is bonded through it's branch circuit grounding conductor.

That leaves the second item. Metallic water systems are to be bonded in accordance with 250.104. All these conductors are sized according to Table 250.66 per 250.104.

So if you have metallic piping running through a house, then you must bond all the piping. Where this bond is broken by a water heater, then the hot and cold piping must be bonded together again, so the hot pipe isn't floating.

If you have an electric water heater, then the heater is bonded by it's circuit's EGC. But the piping entering and exiting the heater must be jumpered by a conductor sized according to 250.104 (Table 250.66). This would have a 10 AWG EGC bonding the heater, and a #4 bonding the two pipes together.

 

[tom baker]

Re: Grounding, EGC;'s from appliances

Dennis, bonding metallic parts of a non metallic water sytem is not required as it is not a metal water piping "system".
In Washington State we have a state rule that isolated metal pipe stubs don't have to be bonded, and a bond is not required at a water heater is there is a mixing valve that creates continuity between hot and cold.

 

[Dennis Franklin]

Re: Grounding, EGC;'s from appliances

Hi, George/Mike.... The item in question is: does the bonding of an isolated appliance, need to be bonded DIRECTLY back to the MAIN PANEL??? When fed from a sub-panel, which is smaller than the Main panel in a large commercial building, and a considerable distance from the MAIN PANEL, which is feeding the smaller (l00 amp) sub panel the appliance if fed from???? New Mexico's Chief Electrical Inspector is requiring ALL APPLIANCES To be bonded DIRECTLY back to the Main Distribution panel, and sized in accordance with the feeders to the Main Panel, instead of the Sub panel.... This gets kinda ridiculous when you have to bond a small water heater in accordance with 250-66, using the Main Feeders to the building, instead of the feeders to the sub panel.....

 

[roger]

Re: Grounding, EGC;'s from appliances

Do you think the inspector is confussing bonding this appliance's piping with thinking it is part of the Grounding Electrode System?

Roger

 

[George Stolz]

Re: Grounding, EGC;'s from appliances

Originally posted by Dennis Franklin:
Hi, George/Mike.... The item in question is: does the bonding of an isolated appliance, need to be bonded DIRECTLY back to the MAIN PANEL???

If we are talking exclusively about bonding the appliance, then no. It's EGC is to run with the circuit conductors to the panel where the circuit conductors originate. It is sized according to 250.122 based on the rating of the overcurrent device supplying the equipment.

When fed from a sub-panel, which is smaller than the Main panel in a large commercial building, and a considerable distance from the MAIN PANEL, which is feeding the smaller (l00 amp) sub panel the appliance if fed from????

Do you understand that this subpanel's rating has no relevance in this discussion? Regardless of the function of the conductor is question (unless you forgot to tell us the subpanel is in a different building).

Ask him to cite a code reference, because what you're saying he's requiring doesn't make any sense.

I would gamble 50? that he's requiring you to bond the two water pipes together, and you're not getting the message.

 

[electricmanscott]

Re: Grounding, EGC;'s from appliances

Originally posted by georgestolz:
So if you have metallic piping running through a house, then you must bond all the piping. Where this bond is broken by a water heater, then the hot and cold piping must be bonded together again, so the hot pipe isn't floating.

If you have an electric water heater, then the heater is bonded by it's circuit's EGC. But the piping entering and exiting the heater must be jumpered by a conductor sized according to 250.104 (Table 250.66).

 

[George Stolz]

Re: Grounding, EGC;'s from appliances

Originally posted by electricmanscott:
The only way that this would be required is if the hot and cold metal pipes are completely isolated from each other. I have not seen a situation where this is the case.

I've never sawzalled a water heater to see.

Or, I guess, tested for continuity.

 

[Dennis Franklin]

Re: Grounding, EGC;'s from appliances

Hi again, The issue here is, if the main service feeders are sized for a 400 amp main, ergo 500 KCMIL, do I have to run a 1/0 ground conductor (art. 250-66) to the appliances for grounding that appliance? The Water Heater in question, is in the same building, but fed from a smaller 100 amp sub-panel in another part of the building, a school in this instance, but we were required to bond the water heater piping, not the heater itself, straight back to the MAIN panel, not to the sub-panel, and then to the main thru the sub panel... AND size the EGC in accordance with 250-66, and use the Main feeders to the Main panel for sizing..... Savvy my problemo??? HELP!!! This isn't an issue about bonding between the hot and cold pipes.... Dennis

 

[George Stolz]

Re: Grounding, EGC;'s from appliances

You see, the problem is that you're giving is conflicting information.

do I have to run a 1/0 ground conductor (art. 250-66) to the appliances for grounding that appliance?

...but we were required to bond the water heater piping, not the heater itself...

This isn't an issue about bonding between the hot and cold pipes.

So which is this conductor installed for? For bonding water pipes, or an EGC for the water heater?

 

[haskindm]

Re: Grounding, EGC;'s from appliances

Dennis,
You need to decide whether you are "bonding or grounding" there is a difference. If the water line is one of the electrodes in your "grounding electrode system" then 250.66 applies. If you are BONDING the waterline to your service, you would also use 250.66 and the conductor should go back to the main service. If you are running a grounding conductor for your branch circuit to the water heater then 250.122 would apply. We need to know what you are trying to accomplish in order to direct you to the correct section of the code.

 

[Dennis Franklin]

Re: Grounding, EGC;'s from appliances

Hi, Mike,etc.... I must sound like a real dummy to you guys, so let me "splain" my situation as is.... I recently installed a new 200 amp 3 phase service on a private school. We installed 2 100 amp single phase sub panels in the building, some distance from the main panel. I fed a small 40 amp electric wate heater from one of these sub panels, with a NO. 8 set of feeders, and a No. 10 ground for the heater. The isolated parts of the metallic piping to this heater was grounded back to the sub panel with a No. 6. grounding wire, and the metallic water piping is NOT part of the grounding electrode system for the building. ( I installed a concrete encased grounding electrode for the system, and an GEC, No. 4 to the main panel). Our inspector told me I had to also provide a No. 4 EGC from the water heater piping, BACK DIRECTLY to the main panel, NOT to the sub Panel, which the heater was fed from. I agree that the EGC has to be grounded back to the main panel, but not directly, bypassing the sub panel from which it was fed, which is grounded back to the main panel also... I guess the question is, does all exposed/isolated parts of the water piping system in a building have to be grounded directly BACK to the main panel, and sized in accordance with the feeders to the main panel??? This issue has occured three times on this job alone, lotsa big grounding conductors running back to the main panel.... I can't find anything in the NEC or NMEC to support this, but I also don't want another confrontation on the next job when this comes up again.... I submitted a letter to the New Mexico Technical Advisory Committee, and they haven't responded...yet....
Thanks, promise to not beat this issue any more, you guys have been very kind in your assistance, I really appreciate that....Dennis

 

[George Stolz]

Re: Grounding, EGC;'s from appliances

Dennis:
I must sound like a real dummy to you guys

The only dumb question is unasked.

Dennis:
and a No. 10 ground for the heater.

So the heater is bonded. Good...

Dennis:
The isolated parts of the metallic piping to this heater was grounded back to the sub panel with a No. 6. grounding wire,...

This is incorrect. It needs to be bonded with a #4. Also:

250.104(A)(1) General. Metal water piping system(s) installed in or attached to a building or structure shall be bonded to the service equipment enclosure, the grounded conductor at the service, the grounding electrode conductor where of sufficient size, or to the one or more grounding electrodes used. The bonding jumper(s) shall be sized in accordance with Table 250.66 except as permitted in 250.104(A)(2) and (A)(3).

Dennis:
...the metallic water piping is NOT part of the grounding electrode system for the building.

Not to beat a dead horse myself, but there wasn't 10' a metallic water pipe underground feeding this school? No sprinkler system? Nothing?

Dennis:
Our inspector told me I had to also provide a No. 4 EGC from the water heater piping, BACK DIRECTLY to the main panel, NOT to the sub Panel, which the heater was fed from.

This is for bonding the water piping as required. The inspector is correct.

Dennis:
I guess the question is, does all exposed/isolated parts of the water piping system in a building have to be grounded directly BACK to the main panel...?

No. They all have to be bonded together. They do not all have to be 'home-run' back. They can be linked together.