Nov 27
Peltier Tips
posted by: Player0 in tips on 11 27th, 2008 | | No Comments »

You should purchase your own peltiers and have a play.  They really are some of the most interesting devices you can purchase today.  Many resellers still sell peltier enabled CPU or GPU coolers that you can bolt directly on to your existing system.  Don’t expect sub-zero results and make sure you have adequate cooling to deal with the extra 200 watts of heat a peltier will add to your system.

It’s always important to determine which side of the peltier is hot and which side is cold.  You can connect a peltier briefly to a power supply and while squeezing it between your fingers tell which side is hot or cold.  If you leave it plugged in for too long both sides will become hot.  Whichever side is cooler is the cold side.  Reversing the leads will change which side is cold or hot.

Always go with potted peltiers.  They have added protection from internal condensation which can occur when generating sub-ambient temperatures.

Peltier leads are annoyingly fragile.  In many cases they are designed to disengage if the peltier becomes too hot.  Most commonly the simple action of bending the wires around will snap them off.  It’s extremely difficult to rewire them.  And peltiers are expensive.

Peltiers work best when sandwhiched tightly between two water blocks.  They are quite fragile though.  Uneven pressure or too much pressure will crack them.  A cracked peltier may even still work somewhat but never to full capacity.  Sometimes they can be damaged with no visible signs of harm.  As far as I know you can test the current draw of a peltier to make sure it is still working correctly.  For example, a 172w peltier at 24v should draw about 11amps of current.

Whatever you cool with a peltier should have some sort of condensation proofing.  This depends on the day and your climate.  A CPU will need to be covered in silicone gel or dielectric grease to prevent moisture from damaging it.  Neoprene foam is also a common insulator.

Always overestimate your peltiers.  Get the largest one you can for the best results.  Don’t rely on the peltier’s temperature delta or input wattage rating to tell you how it will perform in your application.

Peltiers come in many shapes and sizes so make sure you measure accurately.  Thickness may also vary.

Use a thermal interface material when mating a peltier to a cooling block.  CPU grease works great on the hotside.  Many thermal greases don’t perform well at lower temperatures however so use very thin coats or try to find a grease designed for low temperature applications.

If a peltier is overloaded or is not cooled properly it will simply act as a heater.  This can be quite devestating to electrical components.  I’ve had peltiers boil water when a cooling pump fails.

Peltier voltages are usually designated as the optimal for efficiency.  Providing a peltier with more voltage can improve the amount of heat pumped but with reduced efficieny.  If you can cool a peltier enough you can definitely give them a couple extra volts for more cooling power.  Anything more than 10-15% can certainly reduce a peltiers life or cause immediate damage.

Peltiers can certainly be air cooled however this will require a very large surface area and sufficient (loud) airflow.  Cooling air with a peltier is even harder.

Stacking peltiers is a great way to increase power.  You usually want a copper heat spreader in between stacked peltiers.  A dual loop cooling system as I’ve described in my last post is an example of peltier stacking.  Instead of directly mounting the peltiers to each other, a ‘cold’ water loop was used to bridge the peltiers.  This sacrifices efficiency for ease of assembly.