How To Check A Dryer Electrical Supply

Before you begin any dryer repair you should confirm that there is the proper and adequate electrical supply to the dryer. What exactly does that mean? Electric dryers in the US operate on two 110 volt A/C circuits. The two 110 volt circuits combine to deliver 220 volts A/C to the dryer heater.

The dryer motor operates on 110volts A/C. Dryer receptacles have an L-shaped neutral post. You can check the voltage to your dryer by slightly sliding the cord out of the receptacle and using the leads from a multi meter to check for voltage on the blades of the cord that slide into the receptacle. Between the left and the right blades you should read 220 volts. Between the left or right blade to the center blade (the L-shaped blade) you should read 110 volts AC. The 4-post receptacle above has the L-shaped neutral and a seperate ground. It requires a 4 wire cord and the ground wire is isolated from the neutral on the dryer.

Technicians check for voltage when the dryer is attempting to start or not heating for a very specific reason. Checking for voltage without the dryer plugged in does not tell the full story. A dryer heater uses 220 Volts and draws about 20 amps when it is heating. Checking for voltage from L1 to L 2 on a defective circuit may show 220 volts but when the heater kicks in and starts to draw 20 amps the voltage may drop off to 0 volts. Imagine the wiring to your dryer was stranded wire. Stranded wire is composed of a number of small-gauge wires bundled together to make a larger wire. What if all but one of those stands were cut and only one small wire was completing the circuit? Reading voltage at the receptacle without the dryer plugged in you would read 220 volts from L 1 to L 2. However with the dryer plugged in and the heater attempting to draw a heavy current, the electrons (current flow) would be dammed up behind the cut and only a small amount of current would pass through the wire. Certainly not enough to make the heater heat.

There are a lot of things that can cause a partial circuit but the result is the same as the stranded wire example. Many a heater or dryer motor has been changed needlessly because of a loose connection in the fuse box / circuit panel or some other dryer electrical circuit problem.