I have to be careful here that I do not make this too boring, as it is more detail oriented than what I would normally write about at a non-technical forum. If you are a realtor, have you ever had an inspection report where the inspector made some comment about the "bonding"? While similar to grounding, bonding is not identical. A bond, in essence, takes two metal surfaces to the same electrical potential vs establishing an earth ground. The earth ground is the electrode out by the meter. The bond is that wire and clamp at the water pipes and/or the gas pipe. That is straight forward enough to check, but one thing that really throws novice inspectors, when we teach this at the Bellingham Technical College home inspection class, is figuring out the bonding differences between the main electric panel and the distribution or sub-panel. Without beleaguering this, at the main electric panel, the neutral buss (white wires) should be bonded to the ground conductors and the two also attach to the panel. This is usually with a green screw or a strap. That is correct at a main, yet at the sub, the ground and neutral wires are kept apart from one another. A sub-panel exists at most condos, and mobile homes, where there is a main breaker out on a pole or at the end of the building. In a sub, the ground goes to the metal panel, but the neutrals float. The top panel below, being a sub panel, is wired wrong. In this condo, the main ground is coming in through the metal conduit that is seen below. The problem is the neutrals and grounds are co-mingled and bonded with one another, hence improper wiring. The solution is pretty easy at this panel, minor changes, but if an inspector sees something like this (indicating electrical work done by an inexperienced party) he or she will usually call for repair and evaluation of the system by a licensed electrician. The issue with having neutrals and grounds bonded in the sub-panel is that this co-mingling of conductors results in the every day ground wire being in use all of the time. In theory this is a safety feature and is not designed to be carrying everyday voltage or current. The lower panel shows a green bonding screw that would be left in place in a main panel, or removed in a sub-panel. I know this is all complicated, if you are not into it, but this is the sort of attention to detail that makes it important to recommend a well-qualified inspector. I have run into literally dozens of inspectors who are doing inspections in the field and have no clue about this rule.

Note the green bonding screw, visible at the right side strap, near the main breaker behind a red wire. This bonds the two busses.

Thanks for looking.

Steven L. Smith

Bellingham home inspector

www.kingofthehouse.com