is my extension cord bad?

[JHZR2]

Originally Posted By: larryinnewyork
Originally Posted By: eljefino
PS if you put a power strip on the end of that cord and stick a voltmeter in I bet it goes under 100 volts when the compressor's running.


eljefino,
Question: Does the compressor actually need to be running ? ? ?
I'm no Electrician, but I always checked for voltage drop by just plugging a Voltage Meter into outlet or end of long extension cord.

The reason I ask is because I live in a Ranch house that's 50 ft. long.
I recently put in a separate line for my sump pump (dedicated breaker).
New line showed 120 V,,,, but so did the old line.


Yes, it must be running.

Just like how batteries see voltage drop under load, the equation is Vterminal = Vopencircuit - Current x resistance

There are pretty standard tables for resistance per 100ft for conductors, as well as what size cord should be used for how many amps for how many feet.

Even decent compressors can have pretty chintzy cords directly wired to them. Of course they can get away with it since the run is only a few feey, so the series resistance added is low between the terminal and the motor. That said, if you need to run a longer conductor set, consider rewiring with a heavier gauge conductor right to the conpressor, as every terminal adds additional series resistance above and beyond the conductor itself. For me to install my conpressor in the book I wanted, I had to run electrical longer. I also wanted flexibility to move it if desired. I wired in 10ga cord and it is perfect.

 

[turtlevette]

You attempted a hot start against built up compression. A motor is usually only rated for a limited number of starts in a row.

A start consumes a large portion of the thermal capacity of the motor. My old company built computer based relays that would calculate the thermal reserve left in a motor in real time. For example if a motor consumes 60% of its thermal capacity in one start, then 2 immediate starts in sequence is not allowed. Once the motor runs long enough to cool itself, a stop start sequence is allowed.

These small motors have a cheap thermal cutout that will heat bend and disconnect, then reconnect when cool. If the compression release worked, you wouldn't have been starting against load. But the motors impedance increased just a little being hot and you may be right on the edge of a successful start with that length and size of cord.

Clear as mud?

 

[sleddriver]

Originally Posted By: larryinnewyork
Originally Posted By: eljefino
PS if you put a power strip on the end of that cord and stick a voltmeter in I bet it goes under 100 volts when the compressor's running.


eljefino,
Question: Does the compressor actually need to be running ? ? ?
I'm no Electrician, but I always checked for voltage drop by just plugging a Voltage Meter into outlet or end of long extension cord.

The reason I ask is because I live in a Ranch house that's 50 ft. long.
I recently put in a separate line for my sump pump (dedicated breaker).
New line showed 120 V,,,, but so did the old line.

Yes, it does need to be running to measure Vdrop. The load draws a certain amount of current. Every wire has a certain amount of resistance depending on its size and metal used.

The test you were doing was just for Voltage with no current. Unloaded. You'd get the same reading if you used 24ga wire. However, the two readings and power delivered to the load, would be much different once the compressor switch was flipped.

 

[HerrStig]

Originally Posted By: sleddriver
Originally Posted By: larryinnewyork
Originally Posted By: eljefino
PS if you put a power strip on the end of that cord and stick a voltmeter in I bet it goes under 100 volts when the compressor's running.


eljefino,
Question: Does the compressor actually need to be running ? ? ?
I'm no Electrician, but I always checked for voltage drop by just plugging a Voltage Meter into outlet or end of long extension cord.

The reason I ask is because I live in a Ranch house that's 50 ft. long.
I recently put in a separate line for my sump pump (dedicated breaker).
New line showed 120 V,,,, but so did the old line.

Yes, it does need to be running to measure Vdrop. The load draws a certain amount of current. Every wire has a certain amount of resistance depending on its size and metal used.

The test you were doing was just for Voltage with no current. Unloaded. You'd get the same reading if you used 24ga wire. However, the two readings and power delivered to the load, would be much different once the compressor switch was flipped.
You probably need a storage scope to see what the start up drop is. There's no back EMF when the motor isn't running.

 

[HerrStig]

I suggest Epay for some 10 Ga wire (or bigger) and a couple of heavy duty connectors. The big box stores have them. Make your own cord. It would also be nice to convert the motor to 220 (some can be) but then you are tied to a 220 source.

 

[Merkava_4]

Originally Posted By: HerrStig
I suggest Epay for some 10 Ga wire (or bigger)


Sure you do! You don't have to pay for it! It don't cost you anything to suggest it!

 

[ZeeOSix]

A lot of people burn up electrical devices (compressors, electric chainsaws, blowers, thatchers, etc) by running them on 100 ft, 16 ga extension cords. They don't understand current draw and voltage drop due to cord resistance.

 

[SHOZ]

You should feel the cord after it's been running especially near the plugs. If it's hot it's either too small of the cord end is failing.

 

[Merkava_4]

Originally Posted By: ZeeOSix
A lot of people burn up electrical devices (compressors, electric chainsaws, blowers, thatchers, etc) by running them on 100 ft, 16 ga extension cords. They don't understand current draw and voltage drop due to cord resistance.


This is the way I understand it: The work's gonna get done whether it be using voltage or amperage. If you don't have the voltage available, the load's gonna pull more amperage to get the work done. Being that voltage is the pressure that pushes the current flow, it can get the work done more efficiently without generating as much heat as the extra current flow does. If the voltage is not available, then the load has to depend on the current flow (amperage) instead of voltage to get the work done. It's the higher amperage draw in the absence of voltage that burns up the wire.

 

[eljefino]

Or think of amperage as flow and voltage as pressure. If you have city water and a decent sized incoming main pipe, it doesn't matter if you run the dishwasher while you take a shower in your house.

But if the required load exceeds the flow available, pressure is going to suffer.

 

[ZeeOSix]

Originally Posted By: Merkava_4
Originally Posted By: ZeeOSix
A lot of people burn up electrical devices (compressors, electric chainsaws, blowers, thatchers, etc) by running them on 100 ft, 16 ga extension cords. They don't understand current draw and voltage drop due to cord resistance.


This is the way I understand it: The work's gonna get done whether it be using voltage or amperage. If you don't have the voltage available, the load's gonna pull more amperage to get the work done. Being that voltage is the pressure that pushes the current flow, it can get the work done more efficiently without generating as much heat as the extra current flow does. If the voltage is not available, then the load has to depend on the current flow (amperage) instead of voltage to get the work done. It's the higher amperage draw in the absence of voltage that burns up the wire.


Yes, electric motors don't like low voltage sources, and will heat up and burn up if they are run on low voltage due to a too small of gauge extension cord.