voltage issues

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elevate

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what is the range of proper operation for equipment. I have seen 5 %
or 10% What would actually happen to the equipment? Also what if the branch circuit could not be separated from the main service and there was heavy loads connected to the service. A contractor claims that the voltage is below what it should be and cannot connect equipment.
 
Most equipment have a tolerance of up to +/- 10% of nominal voltage rating.

Under and/or overvoltage usually leads to inefficiency and increased heat. Some equipment may not function at all.

I don't understnad your last question?
 
I'd think overvoltage is more efficient but wears stuff out faster.
Undervoltage may cause excessive current draw for motors and also wear them out faster.
 
Question 1: Does a UPS mantain and regulate voltage/amperage?

Question 2: Can the Utiliy company do something to prevent the voltage
from droping when big equipment kicks in?

Question 3: What rule of thumb is used when adding big motor loads
with high starting current to existing equipment?
 
A UPS will do nothing to reduce motor starting current and will not reduce the affect that starting current has on voltage sags. It will provide some degree of ride through during a loss of power and some of the more expensive ones will output a nice pretty sine wave and "condition" the power.

Voltage drop due to a motor starting is a function of impedance from the utility generator all the way down to the load, and also a function of the magnitude of starting current. You or the utility can either reduce the impedance seen from the load, or you could reduce the starting current. The utility may have rules in place that might force you to reduce the starting current, so that you are not flickering other customer's lights.

You need to calculate how much the new motor is going to drop the line voltage. You then need to look at other equipment voltage tolerances to see if the sag caused by the new load will cause them to trip offline. VFD's are notorious for tripping offline due to voltage sags caused both by faults out on the utility lines and also by large customer loads coming on.
 
Thanks for the information. I need all I can get. We will start by getting acurate voltage readings when heavy loads come on. Second we will talk to our utility provider to discuss our choices.
 
from the utility generator all the way down to the load

from the utility generator all the way down to the load

This is almost the definition of the Thevenin equivalent resistance. The resistance of the whole power company as seen at a 120v residential outlet (maybe they were using #14 wire) =~ 1/4 to 1/2 ohm.
It's got to be less at the breaker panel.

If you plug a hair dryer or a toaster pulling 10A into this outlet, the voltage will drop (10 x 1/4) = 2.5 volts. That's how I measured it.

If you know your Thevenin value for your particular source, and your motor's initial surge current, you can check on paper if the voltage will stay high enough during the surge.

Your voltmeter doesn't even have to be very accurate, because you're looking for the difference in voltage.
 
Sorry No Code Reference #

Sorry No Code Reference #

I thought the Code is 3% at Main Service Point, 5% on Branch service from service, allowable.
 
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