How To Use a Clamp Ammeter to Test a Pool Pump Motor - Amperage


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This guide shows you how to measure the amperage used by your pump motor. If the Amperage measurement exceed the maximum load amps listed on the motor nameplate, the motor is in an overloaded condition and will heat up and eventually fail.

Step by Step


Step 1

TOOLS REQUIRED - The standard multimeter will not measure AC amperage. You will need to purchase a Clamp Ammeter like the one pictured here to measure your pump's amperage.

Step 2

TURN OFF POWER - Make sure to TURN OFF POWER to your pump before opening up the electrical end of the pump. You will probably be working with 240V so be careful. If you are not familiar with electricity, have an electrician help you. Turn off the power at the circuit breaker to the pump for maximum protection.

Step 3

REMOVE ELECTRICAL COVER - Unscrew the two screws that hold the cover over the back end of the motor. Remove the cover to expose the electrical connectors. You will be measuring the amperage of the supply power coming into the pool motor labeled L1 and L2.

Step 4

REMOVE CAPACITOR CLAMP - Remove the single screw that holds the capacitor and move the capacitor to the side.

Step 5

DISCHARGE CAPACITOR - Place an insulated screwdriver across the leads to the capacitor to discharge the capacitor.

Step 6

SET AMMETER SCALE - Set the meter dial to AC Current. That's an A with a ~ over it.

Step 7

ENCIRCLE ONE POWER WIRE - Position one line lead (L1 or L2) so that the jaws of the ammeter encircle one power lead.  This picture shows the clamp around the red supply line, L1. Do not place the ammeter around both wires. They will cancel each other out. It may be necessary to install a test loop to have room for the meter jaws.

Step 8

CHECK SWITCH AND GOVERNOR - Make sure switch and governor are free of obstructions (if applicable).

Step 9


Step 10

TAKE AMPERAGE READING - Record amperage. This shows a reading of  6.33 amps

Step 11

COMPARE READING AGAINST MAX AMPERAGE - The maximum load amps is shown on the motor nameplate. The picture shows an allowable amperage of up to 7.3 amps with 230V. The recording reading of 6.33 is below the max allowable amperage. Note: Amps shows are 14.6/7.3. This motor can be configured for either 115V or 230V depending on your supply voltage. 14.6 is the allowable amperage for 115V. 7.3 is the allowable amperage for 230V.

Step 12

ANALYZE ISSUES - If the amps are higher than the maximum limits, you have an overloaded condition. Check voltage. If the voltage is low, the amperage will be increased to compensate for the low voltage. Check for obstructions in the motor like a worn impeller that is rubbing against the diffuser or debris wedged in between the impeller and diffuser. Note: If you have a clogged impeller, this will reduce water flow but it will not increase amperage unless the clogged debris is rubbing against the wall of the motor. Work performed by the motor is directly related to the volume of water it must move and the length of pipe it must move it. Reduced water flow caused by a clog means less water moved and therefore less work of the motor. In effect the impeller clog offloads the motor. One other thing to checko is a possible short in the motor.

Step 13

TURN OFF POWER - Turn the power to the pump OFF again at the circuit breaker.

Step 14

REMOVE AMMETER - Take the Clamp Ammeter off of the power wire.

Step 15

REPLACE CAPACITOR - Secure the capacitor with the single screw. Do not touch the leads of the capacitor to avoid a possible shock. Make sure that the plastic cover is in place to provide insolation for the capacitor.

Step 16

REPLACE ELECTRICAL COVER - Replace the cover over the electrical circuits and secure it with two screws.


(1 to 5 of 5)

 Posted: 3/25/2019 

Is it ok if i test the amp wthout removing the capasitor?? Because the pump only 240v / 3.8A

InyoPools Product Specialist  Posted: 3/27/2019 

I would follow the instructions as listed in the guide.

 Posted: 10/13/2017 

Anonymous (amperage reading location) - Ideally, you want to know the amperage going into the motor. If you have a long or undersized wire going between the timer and the motor, your amperage could be different when read at the timer or at the motor.

Anonymous  Posted: 10/8/2017 

Why not just take the reading at the timer?

 Posted: 7/19/2014 

Your guide given with viewer are complete and well expai.