0 down vote favorite Full disclosure: Not an electrician, mostly clueless.

Setting: Home Brewing Beer

Short: 120v DC variable drive motor running full tilt when 240v AC 5500w element is connected to mash tun.

Long: I have a 50 gallon brew kettle with a 240v 5500w AC heating element. The element has variable power supply. Recently I added a 120v DC variable speed motor to agitate the mash (stirring 50 gallons of mash by hand gets really old). The motor work appropriately when the heating element is not attached to a power supply; I can adjust the speed of the motor.

When the heating element is attached to its power supply, the agitator motor runs at full speed, and cannot be adjusted. I spoke with the manufacturer and they suggested that I have an electrician come out.

My house was built in the 20's and has lots of "character". Many of the circuits are not grounded. That being said, I am (fairly) certain the circuit that the agitator is running on is grounded, as well as the heating element.

Thoughts? Places to start trouble-shooting?

  • Is your DC motor speed controlled by a pulse width modulator or just by reducing voltage? Feb 23, 2018 at 21:38
  • a picture or a drawing of how you have them hooked up to power would help greatly. But it does sound that the wiring is hooked up wrong.
    – jsolarski
    Feb 24, 2018 at 16:47
  • Get an electrician, we are not electrician stackexchange, get this wrong and things spark, burn, kill.
    – Mr_road
    Mar 5, 2018 at 16:55

1 Answer 1


Check your agitator motor connection. How many wires does it have? Where are these wires connected?

Sounds like you've wired your agitator motor in such a way that when you turn on your heating element, your agitator motor takes the voltage from the heating element as well. So when you adjust your voltage on the agitator motor, it doesn't do anything because it's using the voltage from the heating element (you've connected it in parallel so your original connection of the agitator motor is bypassed so changing its voltage don't do anything).

It doesn't have anything to do with your home wiring. It's got to do with your brewing wiring - your control panel wiring.

Make sure your agitator motor is only connected to 1 circuit where it goes to 1 voltage source. Don't connect your agitator motor parallel with your heating element.

  • The motor itself only has two legs. The motor drive controller has three. The motor and drive are produced by the same manufacturer, and are sold as a unit. The heating element is definitely DIY, with a variable SSR. Both units run on distinct circuits coming from the house. The motor runs on a grounded 120v 8A circuit breaker, and the element runs on a grounded 240v 30A circuit breaker. I spoke with the agitator manufacturer and they sell a pneumatic version as well... I'm thinking I'll probably convert over to that. (And call in a professional electrician) Mar 14, 2018 at 21:15

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