Calculations

[Chesterbelloc]

Embarassed as I am to say... it has been quite some time since I have looked at electrical stuff. Long gone are the 3-years I flopped as a mechanical engineering student.

I cannot seem to remember how this works.

If I were to wire an element rated for 240v at 120v exactly does the Watts drop?

Please include the simple equation I am racking my brain about. I have provided links to the two elements in mind.


http://www.amazon.com/dp/B000BPG4LI/?tag=skimlinks_replacement-20

http://www.amazon.com/dp/B0002YU2YS/?tag=skimlinks_replacement-20

 

[KitB]

Embarassed as I am to say... it has been quite some time since I have looked at electrical stuff. Long gone are the 3-years I flopped as a mechanical engineering student.

I cannot seem to remember how this works.

If I were to wire an element rated for 240v at 120v exactly does the Watts drop?

Please include the simple equation I am racking my brain about. I have provided links to the two elements in mind.


http://www.amazon.com/dp/B000BPG4LI/?tag=skimlinks_replacement-20

http://www.amazon.com/dp/B0002YU2YS/?tag=skimlinks_replacement-20

It would be running at 1/4 the listed wattage, if I'm not mistaken.

 

[lectricbrewer]

I'm not an expert by any means, but I believe I remember it being 1/4 of the rated watts for the element.

So if you have a 5500w element @240v, you will have 1375w@120v.

I'll have to look for the equation though....

 

[samc]

http://www.crownaudio.com/apps_htm/designtools/ohms-law.htm

 

[Chesterbelloc]

http://www.crownaudio.com/apps_htm/designtools/ohms-law.htm

Thanks fellas... I remembered the 75% reduction. I couldn't remember why.

The link is great! I'll give it a listen once I am done the podcast I am listening to currently.


EDIT: I thought it was going to be Podcast... was thrown for a loop by the word 'audio' in the link.

I found this link... http://www.the12volt.com/ohm/ohmslawcalculators.asp

 

[HearthstoneBrewery]

P=IV
V=IR
where P = power (watts)
I = current (amps)
V = voltage (volts)
R = resistance (Ohms)

From those two equations, you can derive this ratio:
P'/P = V'²/V²
where P' is your new power, and V' is your new voltage, and P is the old power and V is the old voltage.

Further, if your new voltage is 1/2 the old voltage (120V versus 240V), then your new power is 1/4 the old power. So if you're running a 240V element at 120V, divide its rated power (watts) by 4!

 

[Chesterbelloc]

Cool. Thanks guys.... I finally found a post that I was looking for.

https://www.homebrewtalk.com/blogs/...boil-kettle-hot-liquor-tun-math-involved-547/


On that note... these look good.
http://www.wattco.com/over-the-side.html