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-   -   120 v heating element (http://www.homebrewtalk.com/f170/120-v-heating-element-377995/)

it99 01-02-2013 02:40 PM

120 v heating element
 
I want to starting adding a heating element to my 7.5 gallon kettle.
Can I just get a hot water heating elelment at Home Depot or where is the best place to get it?

How do wire just directly hook up wires to the plug through ketle?

Is 120v element big enough for 7.5 gallon pot? will it take a long time to boil?

Do you have to treat the element in any way so it doesn't add any impurities into the water kettle? THank you!!

warthog 01-02-2013 08:00 PM

i can help you with this. you don't give a lot of information, so i'll have to make some generic assumptions. but in general, yes it might boil, but it will take while. it also means you get a short thermodynamics lesson too. ;-)

if you want to take a water heating element and add it to your kettle, you should look up some fantastic instructions at www.theelectricbrewery.com. easier is an immersion heater.
the immersion heaters that i've seen, just plug into an outlet at one end, and you stick the business end into the water (PLEASE MAKE SURE YOU USE AN ELEMENT DESIGNED SPECIFICALLY TO DO THIS!!!! - otherwise this is the brewing equivalent of bathing with your toaster). i'd do a quick google search for immersion heaters to find one. then i'd follow the instructions that come with it.

whether you buy an immersion heater, or follow kal's instructions for adapting a hot water heater element, it will take some time to make that water hot.

so how long will it take to heat your water?

here goes:

first let's discuss the element: heaters are rated in watts (the amount of power they use), electric heaters are nice since almost all of the energy going in gets turned to heat (so much so that its pretty safe to use 100%). a 120 vac socket usually has a max of 20 amps. to get the maximum watts on the circuit before the breaker blows you multiply the volts by the amps so your max is 2400 watts (this is not a smart move), it is safer to go at about 80% of this (1920W). i have no idea what's actually available.

7.5 gallons is a decent size pot, i used to use the same size, i would typically heat 6 gallons of water in that. the math is a lot simpler in metric, so we're switching.

6 gallons = 22.7 liters
to boil water you have to transfer energy into the water. the amount of energy needed to change the temperature of something is called the specific heat. specific heat is given in joules/gram times degrees c (sometimes written as J/gK), water is 1.46 J/gK
the amount of energy to raise one gram of water 1 degree c is one calorie, or 4.184 joules.

so you have 22700 grams of water that you want to raise from room temperature (20c) to boiling (100c). 22700*80=181600 or 7598144 joules.

oooooo kaaaaaay..... so what does this mean to you?

you need one more piece of information. watts are power, and joules are energy. power is energy over a period of time. lucky for us, 1 watt is equal to 1 joule per second. so your heater can deliver 1920 joules/second. therefore 7598144 joules/1920 joules/second = 3957.37 seconds, or about 66 minutes. in a perfect world.

as you know, this world ain't perfect. you will have heat loss through the sides of your kettle, and a huge amount of heat loss out the top. plus you have the energy of phase change to deal with as well. all that can be figured out too, but its a little more complicated. we would need to know the diameter and material of the pot, the air temperature, the barometric pressure at your altitude and so on. never the less, we can say that the time will be somewhere north of 65 minutes, and quite likely considerably higher.

hope that helps

prof warthog

skeaterbait 01-03-2013 01:19 PM

Quote:

Originally Posted by it99 (Post 4737785)
I want to starting adding a heating element to my 7.5 gallon kettle.
Can I just get a hot water heating elelment at Home Depot or where is the best place to get it?

How do wire just directly hook up wires to the plug through ketle?

Is 120v element big enough for 7.5 gallon pot? will it take a long time to boil?
Do you have to treat the element in any way so it doesn't add any impurities into the water kettle? THank you!!

So from reading the previous post I gather that the answers are Yes and Yes?

warthog 01-03-2013 02:15 PM

in short, yes. though, if it is a very wide mouth kettle, the heat loss may exceed the wattage of the element, if it is an element smaller than 1920W. and that means, it will reach some maximum temperature below boil, and stay there.

BadNewsBrewery 01-03-2013 03:18 PM

http://gnipsel.com/beer/software/cal...ctric-heat.xls
This spreadsheet answers any questions you may ever have. I found that with 11 gallons in a converted keggle and 66* ambient air, I get roughly 93% efficiency out of my element. Plug in your numbers and see how long it takes for you to get to boil, if ever.

-Kevin

it99 01-03-2013 03:32 PM

thanks for all of the very detailed information. It sounds like it's not too practical to try to boil with 120 v unless you want to wait an hour. If I try 240v element and plug into my dryer outlet will that work? How long will that take?

warthog 01-03-2013 03:47 PM

how many watts?
electricity and water, are a dangerous combination. you can very easily kill yourself, or burn your house down or both. i hope you have someone that can give you some help.
but basically, you can buy 5500w elements. that's 23 amps at 240v (dryers are usually 30a so you're good there). if you use bnb's spreadsheet with 93% efficiency, it says that it'll take you 25 minutes.

good luck, please find a qualified electrician

brewmastercontrols 02-02-2013 11:28 AM

We have a page on our website that allows you to calculate various things related to electric brewing.

Electric Brewing Calculator

It is basically an online version of the spreadsheet referenced above.

SamHain 02-02-2013 12:02 PM

HERES my latest kettle build. Im not very good at writing but you it may help you.

revansCAAD8 02-02-2013 12:45 PM

Here is my 120v HeatStick that I built to assist my stove for faster heating:
http://www.homebrewtalk.com/f51/all-...design-379729/

Robert


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