Epoxy coating · 14D471K: Ø 14 mm, 470 V14D471K markingBent pins · 7.5 mm spacing

Blue or orange flat disc, “14D471K” text on top, two parallel legs
14 mm diameter disc, lead spacing 7.5 mm

Resistors

Varistor

In simple terms

What is this?

A safety gate that is normally closed and opens when the voltage suddenly rises.

What is it for?

Draws a sudden voltage spike onto itself; protects the device behind it.

Where do you see it?

Inside power strips and extension cords; it protects the wires from too much current.

How do you spot it?

A round, flat disc and two legs; the voltage code is printed on it.

Caution:

Do not leave it on its own, put a fuse in front of it; do not experiment on the mains.

Technical definition

A part that passes almost no current at normal voltage but whose resistance drops suddenly once the voltage exceeds a threshold. It draws a sudden surge on the line onto itself, protecting the circuit behind it. It is made from zinc oxide ceramic.

Varistor voltage470 V (±10%)

Body14 mm disc

Schematic symbol IEC and ANSI differ

IEC 60617: the drawing style used in Türkiye and Europe.

Pins 2

1Pin 1Has no direction1

2Pin 2Has no direction2

Features typical

Varistor voltage: 470 V (at 1 mA)
Tolerance: ±10% (K)
Max. continuous AC: 300 V
Max. continuous DC: 385 V
Material: Zinc oxide (ZnO)
Warning: Mains voltage is outside this app's scope
Example part: 14D471K (mains type)

Common mistakes

Using it without a fuseA varistor can fail as a short circuit when overloaded. Always put a fuse in front of it.

Experimenting on mainsThis part is for mains power, but mains voltage is outside this app’s scope. Do your experiments below 12 V.

Choosing a low thresholdThe varistor voltage must be clearly above the normal operating voltage; otherwise it conducts constantly and heats up.

Test with a multimeter

Test whether this part is good with the multimeter on the measurement screen.

Take a measurement

Where it is used

Outlet with overvoltage (surge) protectionPower input protectionSuppressing inductor and motor spikes