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Monday, August 1, 2016
Question:
Re: CQD answer published Tuesday, June 28, 2016 -Voltage Drop
1. Voltage drop; Although Eddie G. answer is not wrong it is an over simplification of the issue. Voltage drop is a huge issue that can and does cause problems. Just stick with your answer it is correct. Richard Loyd
2. I read the response by Eddie Guidry to the CQD of 6-14. One thing Eddie did not take in to account is motor loads. Motor current goes up when voltage goes down unlike resistive loads. While the motors Should have proper overcurrent protection to prevent fires the possibility of the perfect storm does exist, especially for a large number of residential motor applications that are cord and plug connected. It is permissible to use a 20A breaker for a multi-outlet branch circuit and homeowners rarely read the instructions of their equipment and even more rarely check the authenticity "listing" of the equipment they plug in. To make matters worse these units have the lightest gauge cord the manufacturer can get away with, check the temperature of most cords of anything that has been in use for awhile. :( Just a bit of food for thought. No we really cannot control what the end user does and they often get upset with us for telling them it is unsafe. :/ Dave F Wisconsin M.E.
3. Monday, June 27, 2016 Re: CQD answer published Tuesday June 14, 2016 -Voltage Drop The statement "If the voltage drops due to too much resistance in the conductor, then overcurrent will not occur" applies for resistive loads. A motor that is supplied lower than rated voltage will have a proportional increase in current so that the motor can deliver the load horsepower connected to the motor shaft. With properly selected OL protection @ no greater than 115% FLA and short circuit protection up to 250% FLA there can be an overload condition if the motor load is at the motor nameplate HP rating. Gil Martin
A
Answer:
Hey Richard, Dave and Gil, thanks for your comments, there were others but to save space we only included these. I'm sure Eddie knows about the effect lower voltages can have on motors but this is good information for our readers. Many of the rules, or lack thereof, are based on assumptions and we all know what assumptions can make out of you and me!