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Going through an extensive DIY remodel of a "total electric" 60's town-home in Texas.

EXISTING is 200A main panel with neutral bonded to ground consisting of #6 bare solid Cu to cold feed Cu pipe on HW heater. All plumbing is underground Cu back to meter (approx 70' to meter from HW heater). No other grounding apparent; no rods or UFERS.

REMODEL will:

  1. Add a gas service and incorporate gas appliances wherever possible (largest will be combination gas range + 50A oven)
  2. Use PEX from main water feed throughout (all underground Cu plumbing will be disconnected).

QUESTIONS:

  1. How should the 200A main panel be grounded? (Note its currently 30' of #6 to the old Cu water line that will run approx 50' under the slab before it is disconnected)
  2. How (if necessary) should the main water meter and entry line be bonded since it will no longer be bonded to the panel?
  3. How should the new gas service be bonded?

THANKS!

  • Yeah, the problem is, if you're gonna do all-electric, you need a lot more of it. A friend in Indiana has 400A service, and he still doesn't have enough for on-demand hot water heating. ----- By the way, they make furnaces which are entirely gas, and do not rely on electricity at all. Ironically they are not available in the rust belt, where they'd make a great emergency backup furnace. (they can be made to play nice with a smart 'stat and fall back on a mechanical 'stat when the power fails). – Harper Mar 9 '17 at 16:44
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    Sorry for the confusion. We are converting from "all electric" to "gas wherever possible", including a tankless gas HW heater. – ftelliott Mar 9 '17 at 18:00
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Grounding Electrode System

You're going to have to install a grounding electrode system. This is typically done by driving two ground rods spaced at least 6' apart, and connecting the rods together using a properly sized bonding jumper. Then you'll install a properly sized grounding electrode conductor, from one of the ground rods back to the main grounding bus in the main panel.

Bonding Water Piping

You may be able (required) to use the abandoned underground copper pipe as a grounding electrode, if it meets the criteria specified in the code. If the water is supplied to the building through metal pipe, you'll also have to bond the metal supply pipe to the grounding electrode system using a properly sized bonding jumper.

If the plumbing within the building will not be metallic, you don't have to bond it.

Bonding Gas Piping

As for bonding the gas pipe, according to the National Electrical Code, metal piping systems that are "likely to become energized" must be bonded (250.104(B)). So if you have a gas water heater that has no electrical connection, then you don't have to bond the gas piping. If you have a gas fired furnace, then it's possible that you'll have to bond the gas piping.

However, the bonding jumper only has to be sized to the rating of the circuit that is likely to energize the piping. NEC also allows you to bond the piping to the equipment grounding conductor, of the circuit that is likely to energize it. Which means the gas pipe feeding the furnace, can be bonded to the equipment grounding conductor feeding the furnace. And if the gas piping is isolated from the furnace electrical (not likely to become energized), you don't have to bond the piping at all.

In the case of the gas/electric range, again you can use the equipment grounding conductor of the circuit feeding the appliance, to bond the gas piping (if required).

  • Rod pipe and plate electrodes only require # 6 , concrete encased #4 , as I understand the question there was pipe so the wire would not be required to be larger than 6 as I read it. – Ed Beal Mar 10 '17 at 0:18
  • @EdBeal You're right. – Tester101 Mar 10 '17 at 11:15
  • Thank you Tester101 for your answer and thank you @EdBeal for your refinement. Questions: 1. Water service line from meter to house of approx 20' never surfaces in the house. It is tied to the PEX below the slab (I wish the plumber hadn't done that but they did). Also, all prior copper pipe is abandoned and will be replaced by PEX. So, do I still need to bond to the water supply line outside? If so, before or after the meter? – ftelliott Mar 10 '17 at 13:56
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Driving a new ground rod is usually required when removing the metal water pipe from the grounding electrode system. The metal gas pipe needs to be bonded to the grounding electrode system within 5' of entry. I will usually drive 2 rods at least 6' apart this way I don't have to measure the connection and verify that it is less than 25 ohms with my earth tester.

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    Can you cite the code section that requires gas pipe bonding within 5' of entry? – Tester101 Mar 9 '17 at 17:01
  • I know locally it is required or the external pipe requires a separate bond from the internal if not within 5'. Appliances can not be the source of the internal ground – Ed Beal Mar 9 '17 at 20:58

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