Measuring Inrush Current 

This is not an accurate way to measure inrush current. You need a clamp meter with an Inrush button on it that is specifically designed to measure Inrush current which occurs during the first 100 ms of startup. I’ve tested this on my compressor with a Klein CL900 that has both and Inrush button and a Max/Min button. Consistently, I get a reading of 98A for Inrush and for MAX, I get a reading of 76A. It’s not the same thing.

I understand that a meter needs an "inrush current" capability that most meters don't have. The reason being that the inrush current only lasts 3 or 4 cycles (10ms) and goes by too quickly for regular meters to measure. If you put the meter on "max" you are measuring current draw not only on the first 10 ms of inrush, but also on the next 990ms of startup current which is less current draw as the motor gets to full speed and therefore a lower reading than the inrush current value as the two are combined over the 1 second start up. I just installed a new 3 ton condenser, coil, and furnace with a LRA of 77 and I measure 85 amps of inrush consistently using the inrush capability of my meter.

New subscriber here. As a home owner I am trying to add up all my inductive loads for the house and am measuring surge or startup current on the heavy hitters such as my HVAC, Well Pump, and machine tools such as table saw and welder. Thanks again for your video.

Thanks for the info!

It may be beneficial to inform folks about the difference between a hard start kit and a soft start kit. A hard start kit actually will not change the inrush current, it will simply decrease the duration of this spike. A soft-start kit, on the other hand, should decrease that spike peak.

66 is close to 82?

Awesome video, very clear, visually and technically. Thank You!

Quite incredible 10x the avg current

Great video helpful

Fantastic✔Sent this to my HVAC folks since they didn’t know how to use their clamp on meter etc. I want to run my AC on a portable generator so need the new surge amps after the soft start installation. If it’s below 30 amps, I’m good.

I like to see the compressor at 75% of the RLA rating. I take running conditions and refrigerant charge into consideration when checking amps to deciding the health on the compressor I’m working on because amps will fluctuate in different situations

I'm confused! As the inrush current goes down, that's a problem? I would think as long as the inrush current is less than LRA that would be a good thing. Less current, less heat. No?

Are all inrush clamp meters huge?

If inrush measures the maximum current drawn by the compressor, what does the MAX button on the meter do? Thanks.

what model number fluke meter you are using?

I am wondering which breaker you were using for this 66 Amp ?

Does this meter have DC my... yes,no.....¿¿

RLA = Rated Load Amps. Measured amps while compressor is running. LRA = Locked Rotor Amps. A locked rotor is the worst possible case for impedance that leads to the highest measured amp reading.

The problem with trying to diagnose using Inrush Amperage measurements is and I'll quote Fluke Instruments "Inrush amperage can be 4x to 10x RLA" so with out a substrate or baseline amperage, you can't judge wear and tear.

What model fluke meter is that?

Show the difference with a hard start.

Can it measure Inrush DC ?

Missing the most important piece of info "which wire are you clamping your meter to?" Thanks!

Mine just says OL, ALWAYS doesn't matter which wire I put it at, it's annoying

The reason why I viewed the video is to see what wire you're measuring for inrush amps. The video had no information

This video is absolutely misleading. Inrush current measurement can only be performed using meters that have an inrush capability and equipped with inrush button. This guy did the test with the tool, which does not have an inrush option and not measured correctly.

Yea max is similar but not inrush. Inrush is a spike, max is over a duration

I bet the in rush current on a new unit is probably real close to 3X the running amps

Too much guessing for an educational video

You are not measuring an inrush current .