2x 120v 2000W elements on one controller?

[augiedoggy]

Yup. Think about how a GFCI works (a 120V GFCI is a little easier to understand, and for two 120V circuits, we only need to understand the 120V versions.) A GFCI measures the sum of the currents flowing thru the hot line and the neutral line, with current flowing in one direction considered positive, and current in the opposite direction negative, and in US AC circuits direction changes 120 times/second. If the signed currents in the hot and neutral don't add up to zero (within a 6 mA tolerance) the GFCI trips the breaker. Thus all the current in one hot line must flow back thru the neutral in the same circuit. If the circuits aren't kept completely separate in the control panel, then some of the current from one circuit will inevitably flow back thru the other circuits neutral. This will cause unbalanced currents at both GFCI's, and both should trip. As noted in my previous post, grounds don't get involved with the GFCI action, so you can, and should have a common ground.

Brew on

I understand the GFCI concern.

I was referring to the fact that my plug in panels have to be inspected and meet code for some reason (likely the commercial use).

 

[doug293cz]

I understand the GFCI concern.

I was referring to the fact that my plug in panels have to be inspected and meet code for some reason (likely the commercial use).

Sorry, guess I misunderstood what your question was about.

Brew on

 

[augiedoggy]

Sorry, guess I misunderstood what your question was about.

Brew on

Not a problem just figured I should clarify.

 

[JDAK]

Hey guys,

Using the "simple" diagram above, can anyone suggest a power switch that would switch both incoming 120v lines on/off using one switch? Sort of like the idea of an over all panel power switch so that I would be able to ensure no power is being applied until all the connections have been made. Not sure if a contactor is needed or what.

 

[Jayjay1976]

Hey guys,

Using the "simple" diagram above, can anyone suggest a power switch that would switch both incoming 120v lines on/off using one switch? Sort of like the idea of an over all panel power switch so that I would be able to ensure no power is being applied until all the connections have been made. Not sure if a contactor is needed or what.

I see your concern with wanting to isolate power to the unit, I never thought about that when I built my controller. I connect everything up and ensure the element arming switches and pump switch are OFF before plugging in the two power cables. I guess you could add two more switches, contactors would be overkill IMHO.

BTW, this controller has performed flawlessly so far with more than 40 batches brewed, I've only opened it up once just to have a look at the internals but everything was fine.

 

[JDAK]

Fair enough. It does add one more component to mess with. Good to hear the setup is serving you well! What sort of enclosure did you use? Any pics?

 

[Bobby_M]

The switch type you're looking for would be called a double pole, single throw which is often abbreviated DPST. If you're using 1650 watt elements or lower, it can be rated up to 15amps. If you use anything between 2000 and 2250 watts you'll need it to be rated for 20amps just like everything else upstream.

I've argued this before, but there is very little utility in having a means of disabling each element individually. The controller will take care of limiting the total wattage. Let's say you have two 1500 watt elements for a total of 3000 watts and you wanted about HALF power. Well, you could shut one element off and run the other one at 1500/full or you could leave both element on and run the controller at 50% output. The latter solution is exactly half the watt density which is always a good thing.

The last thing to think through here is that you really don't want the power interrupt to happen before the power supply to the controller (DSPR in this diagram). If you do, you'll never be able to mess with the programming or view the probe temperature without the elements being enabled. There is no reason to shut down power to the controller itself. Mine has been powered on 24/7 for 5 years. I mean you CAN wire in a separate switch on the line powering the controller but it can be a low current switch.

 

[doug293cz]

Hey guys,

Using the "simple" diagram above, can anyone suggest a power switch that would switch both incoming 120v lines on/off using one switch? Sort of like the idea of an over all panel power switch so that I would be able to ensure no power is being applied until all the connections have been made. Not sure if a contactor is needed or what.

If you want to switch both 120V incoming circuits with one switch, a Leviton 3032 will do the job. It's DPST (double pole, single throw) as Bobby mentioned. It's rated for 30A, which is a bit of an overkill for this application, but it will work (and it's a part number I remember.) You might be able to find other DPST switches, with lower current ratings, that will also work.

Brew on