PSU for peltiers

What size PSU would I need to handle two 80w peltiers and one 170w peltier?

note: The PSU would be dedicated to the peltiers

At 12 volts you would need a power supply capable of supplying 27.51 amps constant. I would get one that goes higher than that so your not running the poor supply at it's peak capacity. at 15 volts the current is 21.99 amps and at 24 volts the current is 13.74 amps but I dont think the 80 watt pelts are 24 volt units.

JML (Apr 30, 2001 02:10 p.m.):
What size PSU would I need to handle two 80w peltiers and one 170w peltier?

note: The PSU would be dedicated to the peltiers

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TT120
i'm affraid you can't just add all the wattages up and divide by the voltage , it just don't work like that.
The rating of the pelt is not the power drawn but the cooling capacity (Qmax), the power drawn is almost twice the Qmax.
You need to look up the spec of the peltiers, they will each have a Vmax and a Imax. The Vmax is the optimum voltage for best performance (Qmax) and the Imax is the current the pelt will draw at that voltage.
Below is the spec for a 85W pelt;
Qmax=85.0
Vmax=15.8
DTmax=68 deg. C
Imax=10
As you acan see Vmax x Imax = 158W
To power the two 80W pelts at optimum performance would need a 15.8 Volt x 20Amp power supply.
The 170W pelt will probably be 24V so you would need a seperate supply for that of around 24Volt x 15Amp.
Your looking at some serious PSU's there!

Without knowing all the specs on his particular pelt, I just did a quick and dirty calculation which will work generally. Although It's better to have a bigger supply than you need.