Introduction: Power Controller for Hot Water Heater

I wanted to simmer some grated ginger in two gallons of water for several hours to make ginger beer syrup for brewing. This power controller allows me to regulate the boiling vigor, from a gentle simmer to a full-on hard boil.

My Hot Water Heater (described in another Instructable) is a great, large capacity, inexpensive water boiler, but fine control over how vigorous the boiling occurs is a welcome addition.

A commercial power controller from a brew-shop, however, is not inexpensive. How would you like to put one together for around $15? By using common bits-and-pieces from eBay and discarded junk, you can do just that.

This controller will work fine on other non-inductive loads (up to 4000 Watts).


1x Power

Controller (4000 Watts).(Do an eBay search with these terms, and I have included a photo to help your search).

1x Desktop PC Power Supply (PS)-from Junk shop, computer repair shop, Goodwill store.

I electrical extension cord (rated to 15A minimum).

2x zip ties

Power drill.

Small nut, bolt, solder tag.

Step 1: Obtain Parts.


the power controller on eBay. I use a source in China. I have ordered several , and they have all worked fine. Ensure that the input voltage matches your local supply.

Call in and see you local PC repairer and ask if you can have a junked power supply (PS). A busy shop will usually have a few of these lying around waiting to go to the recyclers, and the tech. is usually quite happy to sell you one for a couple of dollars-maybe even give it to you.

Open up the junked PS and strip it. Take everything out-circuit board, wiring harness etc. (You can leave the switch and fan, but they will not be used). Discard what you have removed.

The empty power supply case will be a vacant metal box. (see photo)

Step 2: Mount the Controller.

This is done

when the power controller from eBay arrives.

Stay safe. Do not be tempted to wire the controller and operate it before it is mounted in the PC power supply case.

You can remove the metal mesh surrounding the power controller if you wish. It may make access to the screw terminals easier.

Remove the knob from the controller (it’s a push-fit) and locate the controller inside the case. You will need to mount the controller on plastic or metal stand-offs (rawl plugs work fine). The case of the PS will have at least one side which is sheet metal. Drill a hole through the sheet metal side of the power supply. The potentiometer + knob will poke through this hole. Tighten up the potentiometer nut to secure.

Step 3: Wire Up the Controller.

Cut the extension cord into two equal halves. Pass the wire ends of both halves through the hole where the PS wiring harness exited the PS. Strip the plastic off wires, and connect the plug end of the extension cord to the Voltage Input terminals using the screw connectors. Connect the socket end of the extension cord to the Voltage Output terminals on the controller. Secure the cords with zip ties (tight). Best to have an electrician check your work at this stage. If all is good, re-assemble the PS box.

Step 4: Test the Controller

You can

use a desk lamp (filament bulb type) to test the controller. Plug the lamp into the socket end of the extension cord from the unit. Plug the controller into a wall power outlet. When you turn the knob on the controller, the brightness of the lamp should vary, from totally off to full brightness.

You can now test the controller with the hot water heater.

The power controller runs quite warm in operation.