You were recently hired on as employee number 73 at a small firm that has some manufacturing, assembly, and packaging operations. You are its first electrician, joining Rufus (employee number 29) to constitute the maintenance team. He is the plant’s general repair and maintenance man, and previously worked for 15 years at a local auto dealer that went out of business when the owner died.

The firm started out by ordering a mix of custom and off-the-shelf components to make its products. As time went on, the firm would bring production of something in-house due to buying a CNC machine, 3D printer, or other equipment. This would increase its capacity to develop new products that it could make in-house. The result is an eclectic mix of equipment.

The premises wiring system is also eclectic, to put it mildly. But according to Rufus, it’s all up to Code because he refused to do any electrical work and the company always hired an electrical contractor. But now, Rufus says, there is something wrong with the power. And that complaint to the Plant Manager resulted in your being hired.

What approach might you take to convert Rufus’ vague complaint into specifics that will identify what, if any, power problems exist?

Answer to Quiz

This is the point where Indiana Jones, if he’d been an electrician instead of a tomb raider, would have pulled out a power analyzer. Since you’re the first electrician they have hired, it’s a safe bet your firm doesn’t have one and probably will not spring for one. It’s also a fairly good bet that a local electrical services firm has one and has the expertise to use it to perform a basic power quality audit. Keep this option in mind for later.

Just because the firm hired an electrical contractor doesn’t mean that contractor did work that conforms to Code. You’ll need to do a visual inspection to look for the kinds of mistakes that would create the conditions that lead Rufus to believe there are power problems. Here are some:

• Unbalanced 277V usage. Many times, you can spot this just by looking in a distribution panel to see how the lighting loads are powered. Just count how many circuits are on each phase. If there is an uneven distribution, you probably have voltage imbalance that can be corrected by simply moving a few wires. But “probably” means exactly that. See the first item under measurements in the list below.
• Ground rods driven next to equipment other than transformers. Grounding on the load side serves no purpose, but when it is done it is often done in place of bonding. This kind of error can also result in ground loops which can cause all sorts of problems.
• Missing ground connections. No ground at the service or separately derived source, n connection between the Equipment Grounding Conductor (EGC) and ground, and no connection between ground systems (e.g., phone system ground rod and service ground rod) are examples. These also can produce ground loops, or even flashover between systems.
• Unbonded enclosures, equipment, etc. These will allow dangerous differences of potential to build up.
• Gaps in metallic raceway. If the raceway is being used as an EGC, it needs to be mechanically and electrically continuous. Look also for “vibration dampers” consisting of nonmetallic unions or flex in that run.

Some quick measurements may also help:

• Voltage imbalance. Similar to that first inspection, but you are actually measuring the voltage and calculating the imbalance from those measurements instead of assuming the loads are identical. Measure at each distribution panel, not just at some random point in the plant.
• High neutral to ground voltage. If you go to a 120V receptacle and measure more than a couple of volts, something is wrong. Most likely, there’s a neutral wire running to a ground terminal and vice-versa.
• Voltage loss. The fact that the plant has been expanding means you probably have a lot more connections than you should and fewer home runs than you should. Which means longer conductor length, which means lower voltage at the point of utilization than you should have. This differs from voltage drop, which is a number you calculate when planning a conductor run.

This inspection is likely to produce more than a few hits. Discuss with your boss the financial value of ensuring the plant can continue to run, how to prioritize the work, and the wisdom of following this work with a power quality analysis so the place doesn’t burn down or the equipment burn up.