blog FreedomHVACTech 1200x675 1

HVAC Technician Training: Step 13 Checking Amp Draw

By now we probably know how important of a role electricity plays in the air conditioning system. Fortunately we have tools for checking the electrical components to see if they are working properly. One of the checks we perform is measuring the amp draw.

The word ampere, amperage, amps and current are frequently used to describe the actual movement of electrons inside a conductor. Amperage determines the amount of electrical conversion to another form of energy. Thus, electrical loads are “energy conversion devices”. The devices are used to perform some type of useful work. (motors, transformers, etc). An ammeter is used to measure the amount of electrons flowing inside a wire, or through a load.

For this measurement, the electricity must be flowing. In other words, the part must be working. We use the clamp on type amp meter. It is designed to read the intensity of flow in one wire. So we see the trusty old DL250 again!

Each electrical component has the amp draw rating attached to it or printed on it. The amp draw will change as the voltage changes so the data plate will also tell what voltage the posted amp draw is corresponding with.

Although each electrical component actually draws amps, we usually assume the small relays, contactors and other control devices are sized properly when the unit is designed. On the other hand, the amp draw of the larger components such as electric heaters, fan motors and compressors can tell us the system is working properly. These are effected by dirty systems, undersized wire, refrigerant under or over charged, refrigerant tubing size as well as other factors. That is why it is so important to check the amp draw.

RLA -Run Load Amps     FLA – Full Load Amps     LRA – Lock Rotor Amps

For most accurate measurement, try to keep the wire as close to the middle of the center of clamp. There are lines on the meter to guide you.

Often there is a need to check the amp draw of a small component. Since this will be a fraction reading, (less than 1 amp) you must build you an accessory to use during these test. This is done by taking a piece of thermostat wire and making exactly ten loops. Leave room on both ends to connect the wire to the part. Now clamp your meter through the loop and energize the part. Your meter will now show ten times the amp draw. Simply divide the result by ten and you know the fraction amp draw.

This procedure is used when adjusting the anticipator on thermostats.