A meter reads 112.0 V on a nominal 120 V service. Before you reach for any rule: is that reading in spec, marginal, or out? Put the number on the band gauge in your head first, then commit to an answer.
Here is the resolution. On a 120 V base, the normal band the utility is expected to hold at the service point runs from 114 V up to 126 V. A 112.0 V reading sits below the 114 V floor, so it is out of the normal Range A band and into low territory you would flag. It is not a wild number, but it is not in spec either, and that distinction is exactly what ANSI C84.1 exists to settle.
ANSI C84.1 is the standard that defines preferred nominal voltages and the acceptable bands around them for 60 Hz systems in the United States. It splits the acceptable voltage into two tiers. Range A is the normal band: at the service point on a 120 V base it is 114 to 126 V, which is nominal plus or minus 5 percent. This is the band the utility is expected to stay inside during ordinary operation, and it is the one you check first when a reading comes in.
Range B is the tolerated band that sits just outside Range A. On a 120 V base the Range B high limit reaches about 127 V, and the low side dips to roughly 110 to 114 V depending on edition and condition. A voltage in Range B is allowed only for limited or unusual conditions and must be corrected within a reasonable time, not treated as an acceptable steady state. So a service entrance reading 127 V is not a violation you reject outright, but it is a reading the utility is on the hook to bring back inside Range A.
Now the part new engineers trip on: C84.1 gives two sets of limits, and they are not the same number. The service-voltage limits apply at the service point, the meter or the point of delivery; the utilization-voltage limits apply at the equipment terminals, and they are wider and reach lower because they allow for voltage drop in the customer’s own wiring downstream of the meter. The utilization Range A low limit, for example, sits at nominal minus 10 percent rather than minus 5 percent. When you judge whether the utility delivered in spec, you compare against the service band, not the utilization band. Mixing the two is how a perfectly compliant 116 V delivery gets wrongly called a problem.
Why split them at all? The utility controls voltage at the service point but has no say over the wire run, the load, or the panel layout past the meter. By the time current reaches a motor at the far end of a building, internal drop has already pulled the voltage down. The two bands let the standard hold the utility to a tight number where it has control and give the equipment a wider floor where the customer’s wiring has eaten some margin. For buyers and co-op staff, that means a transformer or regulator spec written to hold the service point inside 114 to 126 V is doing its job even if a motor three hundred feet away reads lower, because that drop is the premises wiring’s account, not the utility’s.
This is educational material, not engineering or procurement advice; confirm any voltage limit or band citation against the current edition of ANSI C84.1 and a licensed professional before you rely on it.
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