T1 Terry wrote: ↑Sat Feb 24, 2018 1:19 pmThe ones we make up to suit 2 relays are 85mm x 85mm x 85mm and this puts the screw holes at each end perfectly placed to mount the 80mm fan screw holes.
The relays themselves are 60mm long and 45mm wide, mounted across the heatsink so the heat dispersing fins inside the tunnel are under the relay base and the thermostat mounted above between the relay and fan ends up as a neat package. Not sure how you would mount the fan on the end with a 5mm smaller cube, but if it has the same amount of fins inside each half I guess it would work ok.
Don't be fooled by the area required for cooling when one of these relays gets into rapid PWM control, even the good quality low voltage drop relays will have the fan running at a 50% duty cycle passing 100 amps through it via 2 relays rated at 100 amps each. Push the load current higher and the duty cycle drops to 75% fan on at a 140 amp load and 100% duty cycle (doesn't turn off) above 80 amps per relay. If you use the cheap chinese relays that you find on evil bay, even at a 50 amp load (25 amps per relay) the fan can not keep the heatsink cool enough for the thermostat to drop out. Be warned also, those cheap chinese relays don't just fail if the get over heated, they have been known to catch fire, so be very careful with just what product you use.
T1 Terry
Fire.. Thats not good. Thanks for the info. I found this before the post.https://www.aliexpress.com/item/High-qu ... a3d5&tpp=1
My guess is it is the one you are using.
I have alot of 120 mm fans from from my pc/overclocking days also several heat pipe (large) cpu coolers . I may look into them as well. Once again thanks!