Higher than normal resistance to current flow in a circuit causes excessive voltage drop. Here’s a few possible culprits:

1) Wiring is smaller than code standard for the amperage rating and/or length of run of circuit.

2) Poor wire splices anywhere in circuit.

3) Loose wire connections at receptacles or switches, especially the backwired push-in type.

4) Corrosion at wire connections or splices.

    The National Electrical Code [NEC 210.19(A)(note 4)] specifies the maximum voltage drop at 5% for the farthest receptacle of a nominal 120-volt circuit, which means 114 volts is lowest allowed. Low voltage can cause erratic operation and damage to appliances, wasted energy, and overheating at the inadequate connections or splices causing the voltage drop—which can lead to a house fire. 

    We test the voltage at a receptacle as part of an inspection, along with resistance to ground. An example of an acceptable reading is shown below.

• • • • • • • • • • • • • • • • • • • • • • • • • • • 

• What problems does having too many electric receptacle outlets on a single circuit cause? 

• Is a house required to have outdoor electric receptacle outlets?

• How I can tell if a receptacle outlet is tamper resistant?

• Why is there a GFCI breaker in the electric panel for the bathroom shower light and exhaust fan?

• What is a false ground, bootleg ground, or cheated ground receptacle? 

• How can adding wood paneling or a wainscot create an electrical safety hazard?

• How can I figure out what a mystery wall switch does?

• How far apart should kitchen counter receptacles be spaced?  

• How far above a kitchen countertop do electrical outlets have to be?

• What is reversed polarity at an outlet/receptacle? Why is it dangerous? 

• How high above the floor do electric outlets/receptacles in a garage have to be?

• How far apart should electric receptacles be spaced in a bathroom? 

• Is an ungrounded electric receptacle outlet dangerous?

• My bathroom electric receptacle/outlet is dead and there are no tripped breakers in the electric panel. What's wrong?  

• Is there an adapter that can be placed on a two-slot receptacle to make it safe? 

• How do the new tamper-resistant electric outlets work?

• Why is there no bathroom electric receptacle in this old house?

• How can I tell if the electric receptacle outlets are grounded? 

• How far apart should the electrical receptacles be placed?

• What are the most common problems/defects found with electric receptacle outlets during a home inspection?

   Visit our ELECTRICAL page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.