Control box for 120 AND 240...is it possible?

[jCOSbrew]

The control panel shouldn't care what element is hooked up or what power source is connected.

 

[BadNewsBrewery]

The control panel shouldn't care what element is hooked up or what power source is connected.

How do you figure? If he has an element hooked up with Hot A, Hot B, and Ground, and he plugs the panel into a 120v source (only supplying Hot A, Neutral, and Ground) his element will never heat up.

 

[jeffmeh]

If you use a 4 wire connector for input power and a 4 wire connector for each heating element, you should be able to design a 240v panel with no additional relays, switches, etc. The 240v elements will use the H-H-G wires and the 120v elements will use the H-N-G wires.

You either connect the 240v input power and 240v elements.
OR
120v input power and 120v elements depending on the application.

As BadNews pointed out, you would not be able to do that with a single set of elements that would run in either mode.

However, I think it is a very good and simple suggestion. In practical terms, it would be difficult to size the vessels and elements appropriately to run at 240v and also at 120v at 1/4 of the wattage. So it may make more sense to have the "full" system with vessels and 240v elements, and the "small" system with smaller vessels and 120v elements.

Two input cables (240v with H-H-N-G, 120v with H-N-G), both terminating at the control panel with something like nema 14-30. The 240v one has a nema 14-30 plug, the 120v one has a nema 5-15 or 5-20 plug.

Two element cables (240v with H-H-G, 120v with H-N-G), both terminating at the control panel with nema 14-30, with the elements wired appropriately.

 

[jCOSbrew]

My suggestion implies some constraints on the design:

* 4 wire input power connection and heating element connections.
* Connect a 120v power cord OR a 240v power cord.
* Heating element cords use the appropriate 3 wires (H-H-G for 240v or H-N-G for 120v)
* 120v input power can be used with 120v elements (like OP requested) as well as PID, pumps, etc.
* 240v input power can be used with 240v (or 120v) elements, PID, pumps, etc.

I think this achieves what the OP requested. Design a panel that can be used with 120v now and 240v later with the appropriate power source, 240v element, and cords. No need for additional components or complexity inside the panel. 240v panel designs are just controlling 1 phase of AC power (just like 120v panels).

 

[BadNewsBrewery]

Design a panel that can be used with 120v now and 240v later with the appropriate power source, 240v element, and cords.

My understanding was that his goal was to have a panel that could run either. 240v today, 120v tomorrow, 240 again on Thursday - depending on where he brewed. So having different elements would complicate things.

 

[jCOSbrew]

120v and small kettle for 2.5 gal batch today.

240v and keggle for 10 gal batch tomorrow.

The 120v power source limits the capacity. If/when you upgrade to 240v power the cost of the element is $20 and it will probably go in a larger vessel. Otherwise there is no reason to upgrade the power source.

 

[Handsaw]

I have another concern of how you get the power into the control panel. If you have two cables hard wired into the panel, there is a danger (in my mind) that the unplugged one would be hot. This may have been covered earlier and I forgot.

 

[BadNewsBrewery]

Absolutely would be hot. I'd say either two separate plugs that go into the panel (single receptical) or a fitting / adapter that converts your 4 wire 240v plug into a 3 wire 120v plug

 

[jeffmeh]

The solutions being discussed only have one inlet for a power cord, so only one power cord at a time.