CTC PAL cooling stack 6 DW only cools to about 11C

[Arne]

Hi All,

our CTC PAL autosampler system has served us extremely well over its first 15 months. However, now the cooling stack won't cool below 10-11C anymore. It used to go down to 4C without issue. The ambient temperature in the lab has not changed. Have you experienced this? Is dust built-up inside an issue? Could the Peltier element be "getting old"?

Thank you very much for any and all advice,

Arne

[uzman]

Dust build up is certainly an issue for peltier cooling systems.
In order to cool the system , heat is generated.

If the heat is not removed , then cooling power will reduce.

Make sure the cooling fan is working properly and clean any dust accumulated on it.
If you can remove the cover , it is better to clean inside also.

Another point is the voltage supplied to peltier element , if it is not nominal , cooling power will drop.

[Arne]

Uzman,

thank you for your advice - those were very good suggestions. I had already checked all of those things. There was no dust, the fan was running well, and exactly 24V were supplied.

We solved the problem by buying new Peltier elements (2x CUI CP60440) and replacing the old ones. The old Peltier elements had simply gotten "weak". I noticed something was wrong when the two old elements together only drew 1.3A at 24V. I also re -applied thermal grease to all the junctions.

With the new Peltier devices the autosampler reliably keeps the samples at 4C.