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# 3 12 volt tecs in series vs. parallel... Ohm's law refresher.

Sorry for the noob question.

I'm sure this will be very easy for some.. but not for me.

If you have 3 15 volt 6 amp tec's (12706) in series... what is the result in a 12 volt circuit? What is the total amperage being drawn on the power source? Are Each of the 3 tec's all receiving 12 volts still? ( my guess is yes).

This is how my a Coolit Eliminator is wired... how ever I have know idea what tec's it uses as there are no markings on the exposed hot sides when removed and the cold sides are glued to the waterblocks.

The thing is... the unit draws very little current... amazing.

What will happen if I wire the tecs in parallel and supply power with a Meanwell S-240-12 12v/18 amp psu? I know the tec's will get hotter and will need a better fan... not sure how to tackle that on yet... maybe a bigger fan and fan shroud.

Really though I am mostly curious about the way it draws so little power with the tec's wired in series and I am wondering what the effect is on the qMax and amperage draw to the psu.
I'm not a genius in electronics but here's what I remember from high school science class:

3 x 12V TEC in series would need 36V as input and each TEC would receive 100% of the input amps.
3 x 12V TEC in parallel would need only 12V as input and each TEC would receive a third of the input amps.

I'm not sure if it has anything to do with Ohm's Law.

My Freezone Elite uses 6 TECs in parallel and draws a total of 72W at 12V.
72W / 12V = 6A
6A / 6 = 1A
Each TEC ends up drawing 1A of the total 6A.

TiGa
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uhh TiGa...not quite 3x 12v in series would be 36v (12x3), 3x 12v at 6a in parallel would be 18a at 12v (6x3). Oh yeah and this is only assuming your power supply can supply that amount. Otherwise for parallel it still multiplies the current but for series if you have a 12v max it ends up 12/3 or 4v per TEC.
Edited by flak-spammer - 5/10/09 at 1:05am
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CPUMotherboardGraphicsRAM
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Quote:
 Originally Posted by flak-spammer uhh TiGa...not quite 3x 12v in series would be 36v (12x3), 3x 12v at 6a in parallel would be 18a at 12v (6x3). Oh yeah and this is only assuming your power supply can supply that amount. Otherwise for parallel it still multiplies the current but for series if you have a 12v max it ends up 12/3 or 4v per TEC.
What I meant was you would need 36V as input to deliver 12V to each TEC in series, a third of the total input.
The same way that 12V as input would give 4V to each TEC, also a third of the total input.

High school science class is kind of far away so I might be wrong.

TiGa
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Hard DrivePowerCase
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Quote:
 Originally Posted by TiGa I'm not a genius in electronics but here's what I remember from high school science class: 3 x 12V TEC in series would need 36V as input and each TEC would receive 100% of the input amps. 3 x 12V TEC in parallel would need only 12V as input and each TEC would receive a third of the input amps. I'm not sure if it has anything to do with Ohm's Law. My Freezone Elite uses 6 TECs in parallel and draws a total of 72W at 12V. 72W / 12V = 6A 6A / 6 = 1A Each TEC ends up drawing 1A of the total 6A. TiGa
Are you sure yours are in parallel... that seems unlikely... mine are in series and I think that is why the draw is so low... no clue really tho... that is why I am asking
Quote:
 Originally Posted by flak-spammer uhh TiGa...not quite 3x 12v in series would be 36v (12x3), 3x 12v at 6a in parallel would be 18a at 12v (6x3). Oh yeah and this is only assuming your power supply can supply that amount. Otherwise for parallel it still multiplies the current but for series if you have a 12v max it ends up 12/3 or 4v per TEC.
Ok... that explains it... they are undervolted to 4 volts and so the amps are reduces as well.

Man... if I run them in parallel.. wow... I wonder if I can cool the hot side with the stock heat sink and fan. I'm going to look up the stock fan now and see how many cfm it puts out... it's a 92mm x 38mm so it probably puts out a lot as is.

BTW... thanks guys!!!
I'm going to have to read it!

The 92mm DFB923812H fan is a Young Lin model rated at 3200rpm at 12v, pushing 63CFM at 38dB.
Here we go... get out the ear plugs!!!
http://www.delta.com.tw/product/cp/d...92x92x38mm.pdf

Might as wll go for the 160cfm model...If that wont do it... I don't know what will... lol
Quote:
 Originally Posted by flak-spammer for series if you have a 12v max it ends up 12/3 or 4v per TEC.
How many amps would those 3 tec's be drawing total if they are 12706 15v/6amp modules (not sure they are... I'm still trying to find out.)

Well I guess we know it draws less than 8 amps because that is the max the molex connectors are rated for. I read what the current and or wattage was somewhere... I need to find that.
15 volt x 6 amp = 90 watts at 12 volt you will need to supply them with 7.5 amp each for 90 watts and yes wire them in parrallel you will need a supply of at least 22.5 amp
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