Peltier element not drawing max Amp

[spikey1973]

Hey people, sorry a very basic but practical question.

I have a peltier element that doesn't cool enough, also it doesn't draw enough current, and actually starts lower then it should and drops slowly afterwards. Now i'm wondering.. what could be wrong here?

i can see 3 possible problems:
1) i can't cool enough on the cooling side
2) it can't get ride of heat generated on the hot side
3) the element is faulty and is only functioning partly. (is this possible or would it not function at all)

how can i differentiate between these problems?

Background story:

I am playing with a perfect draft i got for free from someone who blew up the capacitors on the power supply because he never cleaned the cooling block inside dust clogged the airflow and... all three blew up.

I replaced them with new capacitors of the same value, but also cleaned thing up, probably a bit to much. as i demounted the cooling block and ofcourse the peltier element. Afterwards i found the cooling capabilities insufficient, and stopped using the machine. The person who gave me the broken perfect draft bought a new one, which suffered the same problem so i was asked to replaced the capacitors, which i did but with some hesitation as mine wasn't really functional anymore.

but after i did i found that his works great, and since i had an good working machine to compare with i did some measurements.
and found that his drwas a steady 4.6A and mine starts at 4.3A and gradually drops to slightly below 3.0A.

I double checked the power supply part but that can easily supply a 5A continously, so i feel the problem is either the peltier or the mounting of the peltier. Unfortunately i'm not familiar with peltiers so i'm not sure how to interpret the drop of the current draw. i believe to be a mounting problem, but i did mount it the same way as it was mounted before dismounting it (i believe), but am also unaware what possible problems with a peltier can be and how to test for this.

Hope you can help me out.

Kind regards

Matt

 

[Harald Kapp]

but i did mount it the same way as it was mounted before dismounting it (i believe),

Did you use thermal grease to improve the transfer of thermal energy from the Peltier element to the heatsink?

 

[spikey1973]

i hadn't any available at the time, i re-used what was on there initially

 

[spikey1973]

i decided to take it apart.. and indeed the problem is most likely the cooling paste.. but. i dropped the stupid thing.

looked the part up it up and it's over 60 euro to replace ( type 12847)
which means to me.. 128 np elements and 4,7A which was indeed about what it draws on the working machine (4,68A)

but at this is a very expensive one so i thought to look at some on ebay and indeed found a 12705 element.
this is 127 element and 5A which comes pretty close to the original. ( i believe)

is this a bad thought? any reason why i should not? 4,5 euro instead of 60 euro is a big price difference..

ps: it is temp. controlled so it cant really over cool, just cool to rapid (freeze at the bottom, and since we are talking about beer....)

 

[Hopup]

Delta T value is important when comparing them I think.

 

[spikey1973]

Delta T value is important when comparing them I think.

try, unfortunately i don't have the Delta T from the original,and also don't know how to obtain this.