heating element
By blueyonder, Section Newbies Posted on Wed Feb 20th, 2008 at 08:34:58 PM MST
ac-dc

doing a lot of reading and sum things i remember was. a guy saying that a heating element couldn't see if the power was ac or dc.   but it got me thinking.   if he was right then its possible to use a ac water heating element.   the other type heating element seams to work with dc .for dump loads.   the wire type i mean.   maybe i should have asked the one who said it. but no one disagreed with him.   i thought if he was wrong then sum one would comment .    i am just understanding the difference from AC and DC. so will the water heating element know. sorry i don't know the answer to this. maybe sum one can put me right.

heating element | 9 comments (9 topical, 0 editorial)

Re: heating element (3.00 / 0) (#1) by ghurd on Wed Feb 20th, 2008 at 02:12:35 PM MST (User Info)

The element will not know the difference between AC and DC. The Problem is the Voltage. Check Ohm's and Watt's Laws.  A 5000W 220V heater. How many Ohms?  Then how much power will it use at 12V? G-

Re: heating element (3.00 / 0) (#4) by wooferhound (tim((NoSpamAt))wooferhound.com) on Mon Feb 25th, 2008 at 09:21:26 PM MST (User Info) http://wooferhound.com

Another thing to consider is that You would probably need a Thermostat. That thermostat would be switching High Current connections. A normal water heating thermostat would fry after a short time. W o o f -={(

Re: heating element (3.00 / 0) (#5) by blueyonder (windwoodgood at yahoo dot co dot uk) on Tue Feb 26th, 2008 at 05:48:58 AM MST (User Info)

thanks ghurd and woofer .     its just i see a lot of 12 dc heaters for sale on sum sites .    there not cheap. old post from ghurd talked about small 12dc coffee maker type thing   from flea markets.   as it happens i have one at home. it will boil water from the car cigarette lighter socket  . i also got it from a flea market.    but ghurd said about 5kw .  yes i know i cant use that on a dc system .    it would just buckle the battery plates.     but whare do dc heating element start and finish .also ac heating elements begin     the coffee maker element is 140 watts. so it says .so might use 11 amps.  ive seen 300watt heaters ac.    there are plenty dc elemts for sale . is it just the wattage that is different.   ive taken sum apart its just a wire inside covered in  ceramic or sumthing.   and a outer metal jacket.    so its the wire inside that heats up.     so is it just a matter of watts .  lower is ok for dc and higher you need ac.    why do i want to know. its just the dc rated are so expensive.    while the ac rated are cheap.    looks to me there made from the same stuff. thats what is confusing me.   just a thicker wire inside.  it must be a special wire that don't melt .   when i get interested in sumthing i like to understand it or how it works.   so is it one law for dc and another for ac? its a ill wind that dos no good

Re: heating element (3.00 / 0) (#7) by ghurd on Tue Feb 26th, 2008 at 09:51:13 AM MST (User Info)

The 5000W 220V heater element thing. It would draw 22.7A at 220V. Meaning the resistance is 9.7 ohms. At 14V the element would use 1.44A. Only about 20 watts. G- [ Parent ]

Re: heating element (3.00 / 0) (#6) by wooferhound (tim((NoSpamAt))wooferhound.com) on Tue Feb 26th, 2008 at 07:34:48 AM MST (User Info) http://wooferhound.com

According to this site http://www.familyonboard.com/car_boat_vacuums.html a 12v coffee heater for a car is 120w which is 10a A home coffee maker is 120v at something closer to 900w That would be 90w at 12 volts which is 7.5a <-(i think i'm right here) It's all about the resistance of the heating elements They don't care if you're feeding AC or DC voltage W o o f -={(

Re: heating element (3.00 / 0) (#10) by Airstream on Mon Oct 6th, 2008 at 01:48:24 PM MST (User Info)

Woof, wish it was so but it ain't. "The 120VAC heater used for low voltages" Using E² / R = Watts and E² / P = Ohms  120*120 = 14400 / 900 (watts) = 16 Ohms so...  12*12 = 144 / 16 = 9 watts  24*24 = 576 / 16 = 36 watts  48*48 = 2304 / 16 = 144 watts  72*72 = 5184 / 16 = 324 watts  96*96 = 9216 / 16 = 576 watts  120*120 = 14400 / 16 = 900 watts [ Parent ]

Re: heating element (3.00 / 0) (#8) by blueyonder (windwoodgood at yahoo dot co dot uk) on Thu Mar 6th, 2008 at 06:08:13 AM MST (User Info)

thanks woofer and ghurd . i understand now.                      i get there in the end its a ill wind that dos no good

Re: heating element (3.00 / 0) (#9) by tmcmurran (t_mcmurran@yahoo.com) on Mon Oct 6th, 2008 at 12:26:45 PM MST (User Info)

But it still did not lower the price of these puppies :(  Has anyone looked into RV Service Places for these?  Just wondering if they carry the 12v versions.  Bet if they do that they would still be an arm and your first born. [ Parent ]

Re: heating element (3.00 / 0) (#11) by ghurd on Mon Oct 6th, 2008 at 02:34:38 PM MST (User Info)

Yup.  6 arms, 4 legs and all 3 first born.  If you can find one. That is why many people (and me) believe small scale wind powered water heating with water heater elements is a losing battle. A tempering tank would make a lot more $ sense. Then put the load resistors uder it.  :-) [ Parent ]

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