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Norm Peery
12-11-2015, 08:44 AM
If an out let tests out to having only 89 volts going to it, 1) would a three prong tester show "ok" or 2) would it show unpowered?
Frank Norman
12-24-2015, 11:29 PM
If an out let tests out to having only 89 volts going to it, 1) would a three prong tester show "ok" or 2) would it show unpowered?

Don't know if there's one answer for all makes of testers, but the Marr 0808 and Klein RT100 receptacle testers have small neon bulbs in them. These kinds of neon bulbs are specified to light up by the time the voltage gets up to 90 volts, so probably work on 89 volts.

A greater concern should be the low voltage itself, suggesting that the current is too high for the length and gauge of the conductors feeding the loads. If 89 volts "going to it" means 89 volts at the outlet with no load on the outlet, then other loads and the upstream cables are mismatched, plus if you then draw power from the outlet the voltage will drop even below 89 volts.

What is the voltage at the service entrance? - more than 94 volts means the max voltage drop of 5% from service to point of use is being exceeded, not allowed by most electrical codes. If the supply is less than 94 volts then the problem is outside with the utility, or maybe too many high current grow-ops in neighbouring houses.
Dave Ruth
12-25-2015, 04:54 AM
If you are using a digital meter, there is a good chance that there is not 89 volts, adding load or using solonoid tester may make voltage drop to zero. The neon tester may be enough of a load to do this, or may glow dim.
Jerry Peck
12-25-2015, 06:01 AM
If you measure anything outside the 120-125 volts +/- 5 volts or so, there is a good possibility that there is a problem with the neutral (or poor meter connection at plug-in fittings).

If the neutral is solidly (good connection) grounded and the meter connections are good, the voltage should be the same on both legs (bus bars) and measure the same at all receptacles.

At 90 volts on one leg, there would be 150 volts on the receptacles on the other leg (90 + 150 = 240) as there will be 240 volts +/- to the service.