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morrillt
Joined: 16 Dec 2014
Posts: 56
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 Link Posted: Thu Dec 18, 2014 3:06 pm Post subject: 1/2ing voltage to 5500 watt element by flipping breaker.... |
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Could i just dial down the voltage of a 240v 5500w heating element by turning off 1 of the 2 120 circuits at the box that feed into it? does this hurt anything? Would I be having the BTU's? Is it a linear relationship? would the amperage stay the same? Thanks a bunch! I am a noob when it comes to electricity.
Also as a thought experiment if i got a variable transformer where i can step the voltage down, is that effectively just putting a fader on the heating element? Is this all sound / doable?
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kal
Forum Administrator
Joined: 12 Dec 2010
Posts: 11123
Location: Ottawa, Canada
Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter
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| Link Posted: Thu Dec 18, 2014 3:18 pm Post subject: Re: 1/2ing voltage to 5500 watt element by flipping breaker |
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| morrillt wrote: | | Could i just dial down the voltage of a 240v 5500w heating element by turning off 1 of the 2 120 circuits at the box that feed into it? |
No. It won't work at all. You need the loop closed for current flow and the heating element to run.
For more information on how 120/240V electricity works, see our "Supply Power" section of the control panel build instructions here:
http://www.theelectricbrewery.com/control-panel-part-2?page=3
| Quote: | | Also as a thought experiment if i got a variable transformer where i can step the voltage down, is that effectively just putting a fader on the heating element? Is this all sound / doable? |
Yes. You can use a variac (a fancy adjustable step down transformer). I would expect 30A variacs to be expensive however.
Kal
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My basement/bar/brewery build 2.0
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morrillt
Joined: 16 Dec 2014
Posts: 56
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| Link Posted: Thu Dec 18, 2014 4:12 pm Post subject: |
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Thanks, Kal your the man.
When people talk about heating at 40% duty cycle (saw this in another link) what the heck are they talking about? Are they doing some sort of variac shenanigans?
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kal
Forum Administrator
Joined: 12 Dec 2010
Posts: 11123
Location: Ottawa, Canada
Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter
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| Link Posted: Thu Dec 18, 2014 4:18 pm Post subject: |
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Duty cycle is a set amount of time, typically 2 seconds.
40% duty cycle means the element is on at 100% of that 2 second time, then completely off for the rest. Repeat.
In other words, on at 100% for 0.8 seconds, off for 1.2 seconds, repeat.
This is the way PIDs work. For complete details on this, see here:
http://www.theelectricbrewery.com/control-panel-part-2?page=11
Kal
_________________
Our new shop with over 150 new products: shop.TheElectricBrewery.com
We ship worldwide and support our products and customers for life.
Purchasing through our affiliate links helps support our site at no extra cost to you. We thank you!
My basement/bar/brewery build 2.0
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huaco
Joined: 05 Apr 2012
Posts: 1506
Location: Burleson Texas
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| Link Posted: Thu Dec 18, 2014 5:09 pm Post subject: |
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I in NO WAY condone the fabrication of, or use of this DIY Variac (or Scariac) as the video creator calls it, but it is a hell of a cool gizmo! USE AT YOUR OWN RISK!
https://www.youtube.com/watch?v=P9UjxG8sN1c
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Kevin59
Joined: 03 Aug 2012
Posts: 1047
Location: Fort Collins, CO
Drinking: Imperial Brown Ale
Working on: Oatmeal Stout, IPA
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| Link Posted: Thu Dec 18, 2014 7:15 pm Post subject: |
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| huaco wrote: | I in NO WAY condone the fabrication of, or use of this DIY Variac (or Scariac) as the video creator calls it, but it is a hell of a cool gizmo! USE AT YOUR OWN RISK!
https://www.youtube.com/watch?v=P9UjxG8sN1c |
Well that was fun to watch! 
Somehow the thing I found most interesting in his build were the two drywall screws through the Romex to secure it to the back of the board...
Last edited by Kevin59 on Thu Dec 18, 2014 9:33 pm; edited 1 time in total
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huaco
Joined: 05 Apr 2012
Posts: 1506
Location: Burleson Texas
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| Link Posted: Thu Dec 18, 2014 7:22 pm Post subject: |
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Yeah, the guy is usually on the up-and-up on most of his projects and methods. However, this one is SCARY!
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foomench
Joined: 21 Feb 2012
Posts: 704
Location: Longmont, CO
Drinking: Pinot barrel aged quad
Working on: Flanders oude bruin in barrel, Flanders red fermenting to refill the barrel
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| Link Posted: Fri Dec 19, 2014 8:41 pm Post subject: |
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Besides all the impracticalities of cutting to 120V, it wouldn't cut the power in half, but to 1/4 of the original amount. P = V^2 / R
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kal
Forum Administrator
Joined: 12 Dec 2010
Posts: 11123
Location: Ottawa, Canada
Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter
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| Link Posted: Fri Dec 19, 2014 9:26 pm Post subject: |
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| foomench wrote: | | Besides all the impracticalities of cutting to 120V, it wouldn't cut the power in half, but to 1/4 of the original amount. P = V^2 / R |
True. Run a 240V element at 120V and you get 1/4 the power. So a 240V/5500W element becomes a 1375W element.
I don't think that's what he was originally asking however (unless I'm mistaken). morrillt: I thought you were asking if you could flip one of the 2 breakers on a 240V double pole breaker feeding the element to lower the wattage? That's what my original response assumed. You need to close the loop for any current to flow at all which means both breakers have to be open - which is usually why they're ganged together so that both have to be either on or off as shown in the picture below on the right:
If you meant creating some sort of switching setup to be able to choose between 120V and 240V then foomench is right - you'll get 1/4 the power. 1375W isn't enough to boil more than 2-3 gallons or so.
Kal
_________________
Our new shop with over 150 new products: shop.TheElectricBrewery.com
We ship worldwide and support our products and customers for life.
Purchasing through our affiliate links helps support our site at no extra cost to you. We thank you!
My basement/bar/brewery build 2.0
Last edited by kal on Sat Dec 20, 2014 3:02 pm; edited 2 times in total
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Wiigian
Joined: 31 Oct 2014
Posts: 3
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| Link Posted: Sat Dec 20, 2014 11:31 am Post subject: Re: 1/2ing voltage to 5500 watt element by flipping breaker |
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| morrillt wrote: | Could i just dial down the voltage of a 240v 5500w heating element by turning off 1 of the 2 120 circuits at the box that feed into it? does this hurt anything? Would I be having the BTU's? Is it a linear relationship? would the amperage stay the same? Thanks a bunch! I am a noob when it comes to electricity.
Also as a thought experiment if i got a variable transformer where i can step the voltage down, is that effectively just putting a fader on the heating element? Is this all sound / doable? |
You could use one of these:
http://www.auberins.com/index.php?main_page=product_info&cPath=2_30&products_id=353
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kal
Forum Administrator
Joined: 12 Dec 2010
Posts: 11123
Location: Ottawa, Canada
Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter
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