Amps at boil

[gometz]

Hey everyone,

I'm planning to build an electric control panel to be able to run two batches back to back. I've read people recommend 50A to be as to do this, but often people say this is for batches up to 20 gallons. I'll be doing 10 gallons max, more likely 5-6 gallon batches. So I am wondering if I can get away with a 30A set up. I have 50A going to the room I want to use, but if I put it in the far corner I could only set up for 30A because of the available wiring to get there. Otherwise I'd have to set up right by the sub panel.

So I'm wondering how many Amps would a 5500W element typically require to maintain a boil on let's say 8 gallons? I know this will be dependent on a lot of things like geometry and surrounding temperature, but I want to understand if maybe I could run a two stage set up with only a 10 gauge wire.

 

[mongoose33]

How well insulated is your boil kettle? What is its dimensions? Those things will influence this.

That said--I have a 5500-watt element in my BK. When I want to just maintain a boil, I turn the EZ-Boil in my panel down to around 25 percent power.

Now, is that accurate, i.e., 1375 watts? I suppose.

Curious as to why the wattage at boil is important to your figuring--I'd be more focused on max power so as to heat water or wort as quickly as possible. What am I missing?

 

[bracconiere]

Now, is that accurate, i.e., 1375 watts? I suppose.

i boil 7 gallons on a 1500 watt hot plate 120v....takes a while to get there, but then i have to lower the temp....(not sure if that's relevant)

edit: in fact according to my kill-a-watt meter, to keep it at a boil, it only takes 500-700 watts once it's boiling....

 

[kevink]

You need to chose wire and breaker size for the maximum current draw possible for whatever elements you chose. That being said, two 5500 watt elements on a 30 amp service is not possible. It does not matter what "percent' you plan to set your PIDs to.

 

[gometz]

Thanks everyone. I guess my thinking is if I can wait until the boil starts to start heating the next batches water then it wouldn't draw over 30A, but I also don't remember much from electrical physics in undergrad (or the one electrical engineering course I had to take for my degree).

So maybe I misunderstood it, even if it is turned down it will still draw more than the peak amps? I am trying to design for peak, but not necessarily when all are at 100%, just whether both could be used at once (maybe someone can help explain what the turndown on a PID does then if it's not limiting the amps).

I happened to move my kegerator today which was blocking the sub panel I will be tying into, and it's one 30A breaker and two 20A (the supply is a 50A from the main panel, so that's the true limit). It seems to two 20A breakers control power to the lights of the room and the other to the rest of the plugs (which includes a TV and a window unit, as well as a few plugs in the garage). The 30A is only hooked up to one outlet in the garage, and a junction box. My neighbor who used to be an electrician thinks the previous owner had a welding machine or something similar hooked up at one time.

 

[gometz]

Okay just checked the basic equations P=I*V and P=V^2/R so if the controller is reducing the power (heat input), it is increasing resistance and therefore decreasing the flow. Some of the current will go to heat, but does all of it?

 

[Vale71]

No controller will regulate power by increasing its resistance since this would mean the controller would be turned into a heating element itself and promptly melt.
AC power controllers use a form of pulsed current to decrease the effective power throughput, but during the ON phase of the cycle the element will still be drawing 100% of its nominal current rating.
To actually reduce the current in a continuous manner you'd need some form of voltage regulator (the V term in Ohm's equations) but that's a bit more complex to implement.

 

[Bobby_M]

5500 watts pulls just under 24 amps. The question was about back to back batches. If my kettle is open top, I run 100% output until I get to the boil and then back off to 60% so call that 15 amps. Yes, theoretically you have 15 amps to spare for heating strike water for batch 2. If you use the Steam Slayer on the boil with the lid on, you could get that down to 7.5 amps.

Trying to negotiate two different element outputs to stay within 30 amps will be frustrating and definitely take away from the simplicity and enjoyment of electric brewing especially if you have to manually tune the balance on brew day. One possible way to approach it, in theory anyway, is to have each element output go through an SSVR but use a common potentiometer on the control circuits. As you turn the knob, it adds more effective output to one SSVR and deducts it from the other one.

Side topic: Yes, technically if you have two 5500 watt elements being PWM'd (or waveshaped through an SSRV) at 50% each, the system will flip flop between 48amps during the on pulse and 0 amps off cycle but as long as the cycle time of the system is short enough, it acts like 24 amps continuous in terms of how hot the cable will get and whether the breaker will trip. Typical trip curves will give you at least twice the rated current for longer than your on cycle time would be.

https://www.c3controls.com/wp-content/uploads/2018/12/TripCurve-Fig5-600.jpg

 

[passedpawn]

Okay just checked the basic equations P=I*V and P=V^2/R so if the controller is reducing the power (heat input), it is increasing resistance and therefore decreasing the flow. Some of the current will go to heat, but does all of it?

Nope, controller does not do any of that. It rapidly switches the current on/off to simulate an AVERAGE current. When it's on, it's fully on, when it's off, zero current. But the duty cycle, which is the % time that it's on, dictates the average current. See duty cycle diagram below, and note that when that control signal is high, the element is drawing 23A.

A 5500W element will draw 23A when it's on.

That element will boil 15g easily, and probably could boil 20g (I brew in kegs, so I'm sure about the 15g, never tried 20). That's at room temperatures. If you're boiling in a cold garage, expect less.

I always do back-to-back batches during which I never have more than one element on, but it requires careful planning. Also, note that you can sparge with cold water with very little effect on lautering efficiency (I often do this with batch #2).

 

[gometz]

Thanks everyone for the explanations. I will probably go with the location next to the sub panel where I can draw 50A through the right sizes wire in that case (unless I decide to just back to back it carefully). I realized though that I think I will probably do a RIMS setup with a 120V element, so even then I will need to use the 50A location.

Edit: and just read the 120V RIMS rocket also takes 16A, so would need to run the 50A anyways to heat mash and strike water at the same time anyways... I may rethink the RIMS system.

 

[Bobby_M]

If you take a long hard look at eBIAB, you can easily built two identical rigs that are completely independent and on a 50amp circuit you'll be able to run two batches simultaneously instead of back to back. You weren't asking that but that's exactly what I would do if I need to increase my production and variety at the same time.

 

[augiedoggy]

Just want point out that a shorter pid cycle time matters more in this situation. I always use a setting of one second on my pids but I believe the default of auberins units is higher and someone trying to accomplish the above would want to change that to 1 second if possible.

One a related note I was able to do something like this recently at the brewpub where I upgraded my rims heating element to a combination of a 6000w element paired with a 2400w element for faster ramping times while being able to keep the watt density very low to prevent any cooked on proteins or scorching.(I use 75% which allows me to raise mash temps 10 degrees in one pass at 5gpm flow rate) The brucontrol software I use has a cool feature where you can enter a max output value that it will use regardless of operation in pid or manual pwm mode. This is also a feature I believe some of the EZboil units from auberins also has.

 

[augiedoggy]

Hey everyone,

I'm planning to build an electric control panel to be able to run two batches back to back. I've read people recommend 50A to be as to do this, but often people say this is for batches up to 20 gallons. I'll be doing 10 gallons max, more likely 5-6 gallon batches. So I am wondering if I can get away with a 30A set up. I have 50A going to the room I want to use, but if I put it in the far corner I could only set up for 30A because of the available wiring to get there. Otherwise I'd have to set up right by the sub panel.

So I'm wondering how many Amps would a 5500W element typically require to maintain a boil on let's say 8 gallons? I know this will be dependent on a lot of things like geometry and surrounding temperature, but I want to understand if maybe I could run a two stage set up with only a 10 gauge wire.

I only have a 30a setup at home and do 10gallon brew sessions on a 3 vessel setup.. I use a 4500w element in my HLT which daws about 18 amps, this allows me to run my panel with rims pump and 1800w 240v rims at the same time as heating the HLT water for sparge... I use a 5500w BK element.

Id say if you havent bought anything yet consider 4500w elements (at least for the HLT)... The difference in heat times to a boil for a 10gallon brew in the same dimension kettles is about 10 mins.. I say this because you can actually heat your bk faster with a 4500w element in a partially covered or taller narrow bk than a 5500w element in a wider uncovered kettle. People often stress the faster heating times of more power and dont mention the other criteria.

 

[doug293cz]

Just want point out that a shorter pid cycle time matters more in this situation. I always use a setting of one second on my pids but I believe the default of auberins units is higher and someone trying to accomplish the above would want to change that to 1 second if possible.

...

This is true for Auber PID controllers, but the Auber EZBoil controllers have shorter (and variable) cycle times. At 50% power an EZBoil has about a 33 msec (0.033 sec) cycle time. At 25% and 75% power cycle times are about 67 msec.

Brew on