How to connect a rheostat

Written by skip shelton Google
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How to connect a rheostat
Many variable-speed fans contain a rheostat to control the flow of electricity. (ceiling fan image by Adrian Hillman from

A rheostat controls the amount of electricity that is allowed to pass through by means of resistance. The electrical resistance may come from a coiled wire, metal ribbons, disks of carbon or virtually any substance that creates a significant amount of electrical resistance over a short distance. Rheostat controls are used in some light dimmers, fan-speed controls and power tools requiring speed control. Because rheostats operate through electrical resistance, the shorter the distance the electricity has to travel, the more power is allowed through the rheostat.

Skill level:

Things you need

  • Flathead screwdriver
  • Phillips head screwdriver
  • Wire cutters
  • Wire strippers

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  1. 1

    Disconnect the power at the circuit breaker running to the line on which you will be working. Create a break in the power line to which the rheostat is to be connected. The rheostat will only be connected to the power line on AC current, not the ground. Strip the power line of it's protective shielding to allow sufficient wire to be connected to the rheostat. It is not necessary to overstrip the wire.

  2. 2

    Determine which direction you want the slider to move to determine more or less power. Because a rheostat operates on resistance, you can connect the powered line to either of the two poles. As the rheostat control pole moves closer to the terminal pole, the electrical current will increase due to lack of resistance. Align the rheostat with the poles and ensure the alignment allows slider accessibility and is according to expectations. For example, on many light switches, the "up" position is equivalent to "on." Connecting a rheostat dimmer switch where the "up" position enabled the most power would be equivalent to a light switch position.

  3. 3

    Connect the rheostat to the power line. The poles of the rheostat may be clamp, screw, or have another connection type. Be sure to fully tighten the mechanism used to hold the wire in place.

Tips and warnings

  • Be sure you remove power to the wires while cutting and working with them, or you increase the possibility of electrocution hazard.

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