120 and 240

I know there was a thread on this at some point, just cannot seem to find it. Nonetheless, I have mad an attempt at putting together a drawing that will allow me to use one control panel to run both a 120v kettle and a 240v kettle. Let me be very clear there is no intention to ever run these at the same time. Furthermore, the 120 will be run by a 20amp circuit and the 240 by a 30 amp circuit. There will be two receptabcles for service coming in and two outlets for the kettles to plug into. Essentially, just building one control panel to run my 5 gallon batches and my 2.5 gallon batches. I have thought about the wire gauging, 10 awg will be used for any of the heavy load stuff.

I realize many of the lines cross and this could cause confusion. Hopefully it is obvious where they cross for expediency of drawing sake and where they are intentionally connected. I have omitted some the labeling, again I think most of you will recognize what is going on. My simple question, any reason this will not work?

Thanks for the feedback.


View attachment 120-240.pdf

You should be able to run both - the 240V volt element will be wired across the two hot legs of your power feed and the 120V element will be wired across one hot leg and neutral. But you really need some sort of interlock to insure that both elements can't be on at the same time.

How would you do the interlock? I'm trying to imagine a way outside of just using a breaker. Do they make NC type contactors? That way if 240 was hot to the contactor it would open the 120 circuit, and vice versa? Hmm.... That'd be sexy

This thread? https://www.homebrewtalk.com/f170/control-box-120-240-possible-385636/

hustlebird said:

How would you do the interlock? I'm trying to imagine a way outside of just using a breaker. Do they make NC type contactors? That way if 240 was hot to the contactor it would open the 120 circuit, and vice versa? Hmm.... That'd be sexy

Click to expand...

You don't need to directly switch the current, just the control circuit and they make NO/NC type relays.

So, for example:

If your 120V element is running your mash tun and your 240V element is heating your sparge water & is also used for boil, you could set-up a low voltage relay to interrupt control to the 240V element while the 120V element is on.

This way, while the mash element is off you can be applying heat to your sparge water!

The most elegant solution seemed to be one power input in the panel, with different power cords for 120v (H-N-G) and 240v (H-H-N-G). Then you would plug in the cord you need and go. See the aforementioned thread for details.

jeffmeh said:

The most elegant solution seemed to be one power input in the panel, with different power cords for 120v (H-N-G) and 240v (H-H-N-G). Then you would plug in the cord you need and go. See the aforementioned thread for details.

Click to expand...

You got it. Two separate cords. One for 120 one for 240. Different plugs makes it impossible to make a mistake. Idiot proof...at least John proof.

Read through that original thread and feel free to ask questions. It will take me some time to refamiliarize myself with it, but I recall that we reached a fairly idiot-proof solution using a 3-way switch and a SPDT relay to switch between 120v/Off/240v (N/Neither/H2 connected to the element). If you used the 240v cord and inadvertently chose 120v on the switch, your element would run at 120v (H-N-G, and 1/4 the wattage), so no disaster. If you used the 120v cord and inadvertently chose 240v on the switch, the element would not fire at all (it would only be getting H-G, the switch is blocking the N, and there is no H2 since you are using the 120v cord).

Jps101 said:

You got it. Two separate cords. One for 120 one for 240. Different plugs makes it impossible to make a mistake. Idiot proof...at least John proof.

Click to expand...

Just to be clear, the solution we discussed only had one power input to the control panel, and two separate cords, where only one would be used at any given time.

jeffmeh said:

Just to be clear, the solution we discussed only had one power input to the control panel, and two separate cords, where only one would be used at any given time.

Click to expand...

But why do it this way when 120V is just 1/2 of 240V? You could do the whole thing with one 240V power source and a heavy duty 2 way switch.

tphjr said:

But why do it this way when 120V is just 1/2 of 240V? You could do the whole thing with one 240V power source and a heavy duty 2 way switch.

Click to expand...

To be able to brew at 120v remotely where 240v isn't available.

I'm glad Jeff chimed in - we hashed this out with some other smart folks in the thread he referenced, and I think the end idea was pretty nice - a simple design that prevented you from accidentally screwing something up and shooting 240v into a 120v element. With a relay/contactor, a switch, and some creative wiring it all worked out quite nicely.

Of course, I look at my system and there's no way I'd ever be able to move it around, nor would I want to, so having multiple input voltages doesn't make a lick of sense to me unless you've managed to build a very compact panel and are doing a single kettle BIAB type setup. Or you mount your brewery into the back of a pickup truck or conversion van.

-Kevin