Question about amp draw

I'm converting my rig from stove/e-rims to a full 240V e-HLT, e-RIMS, and e-Kettle build.
Just been racking my brain on how many Amps I'd be drawing when 2 elements are on

I'm planning on using 3500W 240V elements in the kettle and HLT.
So those would pull 14.58A at 240V.

In my RIMS tube, I was hoping I could use my current 2000W 120V (running at 120V of course).
That's 16.67A at 120V.

Now the question arises; If I'm using the HLT and RIMS tube at the same time, is that going to pull 31.25A (14.58A+16.67A) from the circuit? If that's the case, I would need to install a 40A GFI breaker, and #8 wire. Which I can do fine, there is no existing circuit for this build as of yet.

I can of course use smaller elements, but was hoping I could get away with using the sizes I previously said.

I am planning on only ever doing 4-5gallon batches, so yes, I know it may be completely overkill to do this at all. But that doesn't matter to me. DIY FTW.

just so you are aware- i have a "2000 watt" 120v heating element, which i expected to pull about 16-17 amps like you have there, but in reality i measured it at between 14.8 and 15.3 amps, so the ratings are perhapse the maximum possible current draws. ymmv.

edit- nvm the rest im dumb- thinking 3 phase

audger said:

just so you are aware- i have a "2000 watt" 120v heating element, which i expected to pull about 16-17 amps like you have there, but in reality i measured it at between 14.8 and 15.3 amps, so the ratings are perhapse the maximum possible current draws. ymmv.

edit- nvm the rest im dumb- thinking 3 phase

Click to expand...

3 phase would be nice lol

If both were on at the same time it would draw 14.58 on on leg and 31.25 on the other leg.

That doesn't seem right. 31.25A?
In my situation, I'd only have 1 of the 240v elements on at a time. And when boiling, the HLT nor the rims would be on

ikonis said:

Now the question arises; If I'm using the HLT and RIMS tube at the same time, is that going to pull 31.25A (14.58A+16.67A)

Click to expand...

HLT (3500W@240V)will draw 14.58 on two legs
RIMS (2000W@120V)will draw 16.67 on one leg

if HLT and RIMS used at the same time 14.58A on one leg and 31.25 on the other leg.

if only HLT (3500W@240V) will draw 14.58 on two legs

if our only boiling (3500W@240V) will draw 14.58 on two legs

Lechien said:

HLT (3500W@240V)will draw 14.58 on two legs
RIMS (2000W@120V)will draw 16.67 on one leg

if HLT and RIMS used at the same time 14.58A on one leg and 31.25 on the other leg.

Click to expand...

Wait wait. What about the neutral wire for the 120V... wouldnt that carry the return for the 120V element?

I mean regardless, a 30A breaker wouldn't suffice at these wattages.
but 3000W 240V and 1500W 120V should be pulling 12.5A each respectively. Netting 25A total...

Edit:
I will be pulling new 10/3 romex and installing a GFI breaker if this helps calculations.

ikonis said:

Wait wait. What about the neutral wire for the 120V... wouldnt that carry the return for the 120V element?

I mean regardless, a 30A breaker wouldn't suffice at these wattages.
but 3000W 240V and 1500W 120V should be pulling 12.5A each respectively. Netting 25A total...

Edit:
I will be pulling new 10/3 romex and installing a GFI breaker if this helps calculations.

Click to expand...

240v elements draw on each leg A & B
3000W 240V will draw 12.5A on leg A and 12.5A on leg B
120v elements will draw on one leg
1500W 120V will draw 12.5A on which ever leg (A or B)you put it on
Total draw for both would be 12.5 Amps on one leg and 25 on the other

Maybe someone else could explain it better tham I can.

So I would need a 40A+ breaker? Or am I just misunderstanding how a double pole breaker works

May I suggest that instead of a 2000W 120V element, just get a 2000W 240V element. Look for a "Rheem SP10869GL" element.
Here is a link to a source. bostonheatingsupply.com Rheem SP10869GL

This would put you at 14.6A for the 3500W and 8.3A for the 2000W or a total of 23A± - plus pumps et.al.

P-J said:

May I suggest that instead of a 2000W 120V element, just get a 2000W 240V element. Look for a "Rheem SP10869GL" element.
Here is a link to a source. bostonheatingsupply.com Rheem SP10869GL

This would put you at 14.6A for the 3500W and 8.3A for the 2000W or a total of 23A± - plus pumps et.al.

Click to expand...

Good suggestion, I don't electric brew. I was just trying to help with the amperage question.

P-J said:

May I suggest that instead of a 2000W 120V element, just get a 2000W 240V element. Look for a "Rheem SP10869GL" element.
Here is a link to a source. bostonheatingsupply.com Rheem SP10869GL

This would put you at 14.6A for the 3500W and 8.3A for the 2000W or a total of 23A± - plus pumps et.al.

Click to expand...

Well yea, I could do that. Was just hoping to use what I already have with no more receptacles needed

ikonis said:

Well yea, I could do that. Was just hoping to use what I already have with no more receptacles needed

Click to expand...

True. But you mentioned rewiring to have the power available. With the 240V element you can do the job using a 30A feed.

Was just trying to help. Sorry.

P-J said:

True. But you mentioned rewiring to have the power available. With the 240V element you can do the job using a 30A feed.

Was just trying to help. Sorry.

Click to expand...

No no. I appreciate the help. Ive even considered doing this anyways.

I'm just trying to wrap my head around why using one leg for a 120v element would increase the breaker size so much. Unless I misunderstood how it all works, Lechien is saying that my panel would be using 37.5A on just elements.

I apparently seem like I'll be putting a 240v in the rims. As of course that would work 100%

Ok. Try this:
3500W 240V element = 14.6A
2000W 120V element = 16.7A
With the combination of those 2 elements powered at the same time:
Line 1 would have a current draw of 31.25A
Line 2 would have a current draw of 14.6A
Neutral would have a current draw of 16.7A (the returm path for the 2000w element)

The 240V 3500W element draws its power between line 1 & line 2
The 120V 2000W element draws its power from line 1 & neutral.
When using a 240V double pole circuit breaker, the current is monitored in both lines. If either line draws more current than its rated capacity, it will trip.

P-J said:

May I suggest that instead of a 2000W 120V element, just get a 2000W 240V element. Look for a "Rheem SP10869GL" element.
Here is a link to a source. bostonheatingsupply.com Rheem SP10869GL

This would put you at 14.6A for the 3500W and 8.3A for the 2000W or a total of 23A± - plus pumps et.al.

Click to expand...

I agree 100% with this. Sure, you won't get to use your 120V element, but, considering their cost, it's not worth the extra complexity.

One thing about the double pole 240V circuit breaker. If yo use your 120V element, you will have, as P-J said, a big current difference between both 240V legs. That means that, if you use a 2x40A breaker, your will be somewhat adequately protected when both elements are working, but when one of them is off, the other one will be marginally protected at best.

Let me see if I can explain myself:

The 120V element draws 16.7A
The 240V element draws 14.6A
For a total draw of, let's say, for simplicity's sake, 31.3A, you will have an extra 8.7A current capacity on the breaker.
That means that, when both elements are working, the 120V element will have to draw (in case of a malfunction), 25.4A (52% over it's nominal current) to trip the breaker. Not so bad.
In the same scenario, the 240V element would have to draw 23.3A (59.5% over nominal). Again, not perfect, but not terrible.

But if one of the elements is off...

The 120V element would have to draw 23.3 extra Amps (a 139.5% over nominal) to single handedly trip the breaker.

The 240V element would have to draw 25.4 extra Amps (a 174% over nominal) to do the same.

In both cases, while not extremely bad (I've seen worse), you will be left with some pretty charred elements, in the best of cases.

Again, unless you have a real good reason not to, it's always good practice to keep your loads balanced.

I've been convinced, I'll be going with these elements:
HLT: http://bostonheatingsupply.com/rheemsp10869kl240v3500wss.aspx
RIMS: http://bostonheatingsupply.com/rheemsp10869gl208240v15002000wss.aspx
Kettle: The 5500W ELD on http://www.plumbingsupply.com/elements.html

Build thread to come later as I receive more parts in.

Sounds good.

ikonis said:

Build thread to come later as I receive more parts in.

Click to expand...

Just remember, in build threads, pictures are mandatory...