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Build A Rheostat Receptacle

How To Build A Rheostat Receptacle


Wiring electrical devices can be dangerous. If the instructions are not followed correctly, electrical shock or fire could occur. If you are not comfortable doing this project on your own, please find someone who is qualified to do it for you. Herp Center and myself hold no responsibility for injuries occurring as a result of using this information. Use at your own risk.

What is a Rheostat

A rheostat is an adjustable resistor used in applications that require the adjustment of current.
In our rheostat it can be used to adjust/dim lights, heat pads, and heat tape.

Rheostats are best used when the ambient temperature outside the enclosure stays close to the same temperature. It will take you several hours to a day to get the temperatures set. You will slowly adjust the dial and wait a hour or more and check the temperature. Repeat the process until the temperature stays at the desired temperature. Rheostats will not turn your heat pad on and off or up and down. It only regulates the current to the connected device. It is advised to regularly check your temperatures and adjust the dial accordingly.

You should use a digital thermometer to check your temperatures. The probe should be placed on the substrate directly on top of the heat source for an under tank heater. If you are using it for a light to control a basking temperature, the probe should be placed directly on the basking spot. If you are using it to control ambient temperatures the probe should be placed on the warm side of the enclosure and you should have a separate digital thermometer for the cool side of your enclosure.

Tools Required

Phillips Screwdriver
Wire Cutters

Materials Needed

Dimmer Switch ($5.27 Wal-Mart)
Receptacle ($5.27 Wal-Mart)
4" Electrical Box ($1.02 Home Depot)
4" Box Cover for switch and Receptacle ($1.14 Home Depot)
Romex clamp connector ($1.54 Home Depot)
plug end ($3.48 Home Depot)
2' of rubber cord ($2.36 Home Depot)

This is picture of all the parts before assembly.

Rheostat Receptacle

The very first thing you are going to want to do is grab the 4" Electrical Box and knock out one of the knock outs in the corner as pictured below. They push out fairly easy.

Rheostat Receptacle

Next we will prepare the cord. You will have to strip the outer most shield that contains the three inner wires. The picture below shows what the side that connects to the plug looks like when stripped and ready to attach to the plug.


As you can see the outer most shield is stripped back about 1 and a 1/4 inches. The three inner wires are stripped about 3/8 of an inch. Be sure not to cut the shielding on the three inner wires while stripping the outer shield.

We will now attach the plug to the cord. Make sure you attach the wires to the correct wire clamp. Connecting them incorrectly can cause electrocution and or burn out the connected device much faster then normal.

Rheostat Receptacle

The green/ground wire connects to the rounded looking pole. The white/neutral wire connects to the smaller of the two flat prongs. The black/hot wire connects to the widest prong of the plug.

Once the wires are securely connected to the correct wire clamps you can now install the shield to the plug. Below is a picture of the plug fully attached to the cord.


We will now move on the other side of the cord. You will now have to strip the outer most shield to expose the inner wires. You will want to expose three to four inches of the inner wires.


Be sure not to cut the shielding on the three inner wires while stripping the outer shield. On the end of the three wires you are going to strip off about a 1/2 inch.

Set the cord to the side we will get back to that in a few moments. Grab the 4" Electrical Box and one of the Romex clamp connectors. Install the clamp connector on the box in the hole you already knocked out. Make sure the connector is tightly attached. This is what holds the cord securely to the box.

While we have the Electrical Box in our hand lets also grab the Dimmer Switch. I had to clip off the corner of my switch because the little piece where the screw goes to hold the front cover on was in the way. I also had to break off the little tabs on the side where the Receptacle. My had spots where they are made to break off when bent with pliers. See image below.

Reptile Rheostat Receptacle

Now that we have the Electrical Box and Dimmer Switch in front of us grab the Receptacle and prepared Cord. Slide the end of the cord where the three to four inches of wire are exposed through the hole in the Electrical Box.

You will then Grab the green wire from the Cord and Dimmer Switch and twist them together. Once twisted together fairly well attach them to the green screw on the bottom of the Receptacle as pictured below.

Heating Rheostat Receptacle

Now connect one of the black wires from the Dimmer Switch to the side of the Receptacle with the brass screws. If you are unsure which screws are brass you can look on the back of the Receptacle. It will tell you which side to connect the black wire to. As always the picture is below.

Rheostat Receptacle

Now connect the white wire from the cord to the other side of the Receptacle.

Rheostat Power Box

Make sure the wires attached to the Receptacle are securely attached!

I like to wrap electrical tape around the Receptacle as shown below because installing this in the box keeps everything pretty close so it helps protect it from shorting out if something should shift in the box.

Rheostat Box

You should now only have two wires left that are not attached to anything. You should have the black wire from the Cord and a black wire from the Dimmer Switch. You should now twist these two together and install a wire nut.

Heat Rheostat

Again I like to secure the wire nut with electrical tape as shown below. It is purely a precautionary step I like to take.

Power Rheostat

You will now attach the Receptacle and Dimmer switch to the face plate with the screws provided in the packaging. Once you have them attached to the faceplate then tuck the faceplate into the 4" Electrical Box. Neatly positioning the wires so they do not get smashed. Attach the faceplate with the two provided screws to the 4" Electrical Box. Tighten down the two screws in the romex clamp connector to secure the cord to the box.

This is what your final product should look like.

Completed Rheostat Receptacle

To test that you did everything correctly grab a lamp and plug in in to the Receptacle. Place the box on the floor. Make sure the Dimmer Switch is set to the off position. Plug in the Cord to the Rheostat Receptacle. Do not touch the metal box at this point. Turn on the dial on the Dimmer Switch. If no breaker blew and the light gets bright and dims down as you turn the dial everything is correctly installed. It is now safe to handle the box while it is plugged in.

Congratulations you have now built your own Rheostat Receptacle.


Author: George Fischer
Images - © George Fischer