# Thread: formula for temps with pelts..

1. ## formula for temps with pelts..

How do you know how cold your cpu will be with a certain pelt or do you jsut guess??

Let say my cpu puts out about 80W....at a room temp of 27C how do i know how cold it would be with a 150W or 220W pelt?

2. This is a formula I got from gideontech. It gives the temp difference you would see for a pelt with respect to ambient, I think it is close enough, although it will probably be way out in someones opinion:

Delta T = (1 - (heat load/max cooling power))*max temp difference

So for an 80w cpu and a 150W pelt, and let's say the pelt has a max tmep difference of 67 degrees between hot and cold sides:

Delta T = (1 - (80/150))*67
T = 31.266, so CPU temp would be 31.266 degrees below ambient, giving -4.266 degrees celcius.

this is of course assuming :
A. You are running your pelt at its' rated voltage and current, otherwise you would n't have a 150W pelt.
If your pelt is rated for 15V, and you plan to use it at 12V, make sure you adjust its Wattage rating. I am buying a 220W pelt for my CPU, but as I will only run it at 12V, it goes down to 176W.

B. You have absolutley no extra heat being added to the coldplate or pelt by badly done insulation. Badly insulated coldplate bolts, and inadequate foam insulation and PCB insulation lead to heat being introduced into your system and reducing the effectiveness of your pelt.

I'm not sure if this equation is totally or partially accurate, but from experience with my GPU, it is close to what I expected.

3. Also keep in mind that the Delta T rating for the pelt is rarely if ever achieved. If it is rated at 67C , you would be lucky to get 40-50C under load.

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