Air compressor reset

[Susquatch]

I have a Fluke77III, doesn't look like it measures capacitance.

He found it under the seat of the car he just bought.

 

[Susquatch]

I have a Fluke77III, doesn't look like it measures capacitance.

That a pretty good little meter, but yes, no capacitance.

If you really want that ability but don't want to buy another multimeter, you can wire up a little circuit and use some resistors and some math to help you measure capacitance.

 

[mickeyf]

Maybe there is one under the seat of that car you just bought.

Only thing I ever got that way was an old but usable pair of vice-grips. But I only paid $5 for the car.

While a plain vanilla ohmmeter won't tell you the capacitance, it can tell you if the thing is is dead open or shorted. And analogue VOM is nicest for this. From discharged, it should read close to zero ohms rapidly rising towards infinite or at least a very high value. If it stays at zero consider it shorted. If it starts at extremely high and stays there, consider it open.

 

[Susquatch]

Only thing I ever got that way was an old but usable pair of vice-grips. But I only paid $5 for the car.

Ya, but you are not @David. He regularly craps out horse shoes.

Most of us are fairly confident he has a shop full of elves to do all his projects for him too. His completion rate isn't possible any other way.

 

[jcdammeyer]

Unfortunately I don't have an ammeter

I do...

 

[jcdammeyer]

I do...

I also have a capacitor ESR meter. As capacitors age the Equivalent Series Resistance goes up. Normally only an issue with switching power supplies.

 

[David]

My clamp meter arrived today. Should be able to get a reading off the compressor tonight.
On a 220V circuit do I measure both legs at once?

 

[YotaBota]

IIRC, you need to wire each wire individually

 

[David]

I will measure at the panel

 

[David]

Measured startup amperage on both legs; 17.2A and 17.3A so that seems within spec. Steady state draw is 4.7A

 

[slow-poke]

More telling what the current draw is just before the compressor cuts out or the overload trips. Current should increase as pressure increases, because the motor needs to work harder as the pressure builds.

 

[Susquatch]

On a 220V circuit do I measure both legs at once?

IIRC, you need to wire each wire individually

Yup, one leg only. The exception to this is circuits with a neutral and unbalanced loads.

More telling what the current draw is just before the compressor cuts out or the overload trips. Current should increase as pressure increases, because the motor needs to work harder as the pressure builds.

^This

 

[Elektrishun]

More telling what the current draw is just before the compressor cuts out or the overload trips. Current should increase as pressure increases, because the motor needs to work harder as the pressure builds.

Exactly

@David

Hopefully, you can see the current just before the thermal overload opens the circuit.

 

[YotaBota]

IIRC, you need to wire each wire individually

Sure glad you can read what I mean and not what I write. lol

 

[Chicken lights]

Dumb question - are there ammeters for AC and DC? Or is an ammeter neutral?

 

[Elektrishun]

Dumb question - are there ammeters for AC and DC? Or is an ammeter neutral?

Yes - different meter setting for AC and DC.

Some meters will only measure AC or DC. Some can measure both.

Edit - I am referring to the "clamp style" only.

Meter on left only measures AC amps.

Meter on right can measure both AC and DC. It has 3 different settings for different ranges of measurement, too.

 

[David]

From what I can tell it runs till the pressure switch kicks it off then it won't start again unless I reset the overload.
Tonight I ran it till the pressure switch kicked in, used my spray gun till it should have kicked in again but it never did.

 

[Elektrishun]

From what I can tell it runs till the pressure switch kicks it off then it won't start again unless I reset the overload.
Tonight I ran it till the pressure switch kicked in, used my spray gun till it should have kicked in again but it never did.

I think it will be a 2 man job.

One person observing the meter and the other making the compressor cycle on and off.

What you should see at the meter before the thermal overload trips is enough "excess" current to heat up the bimetallic strip of the thermal overload before it bends and opens the circuit.

Edit - I think I see now. Sorry, wasn't picking up what you were laying down...

The compressor initially runs and shuts off in what appears to be normal operation. Then, it doesn't cycle on after that. That's when you find the thermal overload in the tripped position - correct?

 

[David]

I think it will be a 2 man job.

One person observing the meter and the other making the compressor cycle on and off.

What you should see at the meter before the thermal overload trips is enough "excess" current to heat up the bimetallic strip of the thermal overload before it bends and opens the circuit.

OK I'll wrangle a kid to help me.

 

[Elektrishun]

OK I'll wrangle a kid to help me.

Hold on, I edited my previous post.

Please read.

If the thermal overload is tripped it should only happen when current is being drawn by the motor. Therefore, using the meter and watching until the end of the cycle there should be an increase in current to heat up the thermal overload to cause it to trip BEFORE the end of the cycle.

EDIT - Unless, when the compressor is attempting to start a second time, and the motor is trying to start, can't, heats up, and trips the thermal overload.