It is my understanding that a voltage drop greater than 5% is conducive to higher resistance which can lead to heat. Can you confirm this is an issue for GFCI protected branch circuits as well? Thanks.
Voltage drop is generally related to resistance, but should not be noted in these lower ranges unless there are interrelated issues. There has been much discussion about this, and I do report on excessive VD, but this particular reading wouldn’t give me much concern.
What do you generally consider excessive?
I don’t get too excited until I start seeing drops in the range of 10% or more, but again, there needs to be additional concerns before I start deferring to Sparky.
I think it’s important to get some education/information before we arbitrarily start mentioning voltage-drops as an issue.
In the original picture, even though the drop was measured at 9%, the voltage is still at 112V, which is well within the acceptable limits of any appliance or equipment that would use this outlet. Even at 15%, the voltage would have been near 105V, which is still acceptable in most cases.
Also, the drop was measured using a 15 amp pulse (actually a 12 amp pulse extrapolated for 15 and 20 amp loads), which is likely more than would actually be loaded on the circuit at any given time.
Now, if the original standing voltage was 105V, and there is a 12% drop with a 12 amp load, then we’re looking at less than 93V, which may not be adequate for some equipment.
This is just one example. There are many variables to take into consideration when looking to report on VD during a home inspection.