To bond or not to bond, that is the question? I must tell you that I become foggy on the issue every few years and I have to go back and refresh my memory banks. I was glad when Geoff Stewart from Lincoln City, Oregon shared the image above with the green wire and then asked his fellow inspector friends at the American Institute of Inspectors, “I found a #10 stranded wire from the electrical panel grounding bus bar to the incoming propane tank pipe. The main house ground was a good UFER so why would this be done? The panel itself was wired by a Master Electrician. In fact, it was really gorgeous, so it makes me wonder if this is wrong or right?”
As usual, Geoff has asked an important question that troubles most home inspectors at one time or another. If this green wire was really important, then why don’t we see it every time a gas or propane pipe comes into a home? There seems to inconsistency with it’s use and seems to have more to do with a particular AHJ’s (Authority Having Jurisdiction - Code Enforcement Official) understanding or misunderstanding of the National Electric Code (NEC) and the International Residential Code (IRC). This apparent random application of the codes by the AHJ makes it even harder for the private inspector to figure out when and why it is needed.
- Is it another main house ground?
- Is it done to protect the electrical panel?
- Is it ever going to be energized?
- Is it for bonding or is it for grounding?
And with those four questions I know that I have lost nearly everybody reading this blog post except for the home inspector that is currently struggling with the issue (I can see your eyes glazing over). So I’ll say goodbye to the rest of you friends and forge ahead for the sake of Geoff.
Longtime Oregon inspector Nathan Buckley shared with Geoff, “Research bonding.” Nathan has also been down this road a time or two.
I responded back to Geoff with:
This information may help as you study more, per Nathan’s recommendation. From our local gas company’s “Good Practices for Gas Piping and Appliance Installation” guide book…
BONDING – The permanent joining of metallic parts to form an electrically conductive path and continuity to safely conduct any current likely to be imposed.
So what you are looking at is not a main house ground, but a bonding of the metallic parts.
This may also help from the IRC…
SECTION G2411 (310)
G2411.1 (310.1) Gas pipe bonding.
Each above-ground portion of a gas piping system that is likely to become energized shall be electrically continuous and bonded to an effective ground-fault current path. Gas piping shall be considered to be bonded where it is connected to appliances that are connected to the equipment grounding conductor of the circuit supplying that appliance.
Michael Leavitt – Orem, Utah – www.TheHomeInspector.com
Geoff then responded with
“Yeah, I have a (very) basic understanding of bonding but this small propane tank serves only the gas-log fireplace in the home. It's the only gas appliance in the house. So:
250.104(B) Other Metal Piping. Where installed in or attached to a building or structure, a metal piping system(s), including gas piping, that is likely to become energized shall be bonded to the service equipment enclosure, the grounded conductor at the service, the grounding electrode conductor where of sufficient size, or the one or more grounding electrodes used.
"Likely to become energized" is the thing that I don't get. Would the blower fan in the unit be the reason to bond? This is not a strong area for me yet so thanks for all your input.”
Geoff, we are NOT trying to protect the blower fan with the green wire bond. We are trying to interconnect all of the metal parts that might become energized, and in this case the blower fan could be the culprit that energizes the piping and makes it “likely to become energized.” If there was nothing electric on this propane line, then the codes would not require bonding. And if the fireplace had a permanently connected blower fan that had a 3-wire hook-up with a direct ground back to the panel, then it would provide all of the bonding the metal propane piping would need, but since these blower fans are usually 2 prong plug-in models, then the metal portions of the fireplace and the gas line are not bonded to the electrical system. Even if it had the 3-prong plug, many homeowners unplug the fireplace blower fan and that would give you an unbonded situation, and your exterior green wire bond in the picture removes the ability for a homeowner to easily (accidentally) defeat a bonded system. It makes perfect sense to me, but it is still probably a bit cryptic, so let me provide you with the 2012 IRC Commentary on the code citation above. Hopefully it will clear up the muddy water and give you a more concise understanding of how gas piping is “likely to become energized.”
Hopefully the above clears up the issue as to why we don’t see more gas pipe bonding.
Michael Leavitt - Orem, Utah - www.TheHomeInspector.com