Heat Distribution on Heated Bed

[ex-egll]

Hi, I am only running 20A through the relay, not 60A (it would probably have vapourised on first contact!)

If you look at the label on the relay and it has the UL and CE markings one above the other AND "Made in Taiwan" on the label it is probably genuine. If UL and CE are side by side and NO "Made in Taiwan", probably a copy.

[uncle_bob]

Hi, I am only running 20A through the relay, not 60A (it would probably have vapourised on first contact!)

If you look at the label on the relay and it has the UL and CE markings one above the other AND "Made in Taiwan" on the label it is probably genuine. If UL and CE are side by side and NO "Made in Taiwan", probably a copy.

Hi

If the SSR is *rated* for 60A, then you *should* be able to put 60A through it. Whatever voltage drop you measured at 20A, will just get higher at 60A. If the drop goes to 1.5V at 60A, then it would dissipate 60 * 1.5 = 90W. The "large" heatsinks they sell you to go with these relays are only good to about 20W. It is reasonably certain that your SSR either was defective or a fake. Virtually 100% of all this stuff is made in mainland China these days. It is unlikely that even a legit part would have "Made in Taiwan" on it.

If you got it off of one of the auction sites, and bought it from a random low cost seller - it's most likely a fake. Blowing up at 20A makes it a bad fake (there are perfectly good ones ...). Even buying from distribution, it can be tough to sort out who has what. I got my latest batch on Amazon and got lucky. It's barely a step above the auction sites, but you have a little better ability to get your money back when the part is totally bogus. That of course assumes it's shipped / sold by Amazon and not "Uncle Bob's Fine Pile of Junk".

Bob

[ex-egll]

Got fed up with the Solid State Relay approach! grabbed a 10k resistor and a Power MOSFET, soldered the MOSFET casing to a strip of brass, put thermal compound on the back of the brass strip and bolted it to the SSR heat sink. Connected it up to the RUMBA, Power Supply and heated bed, powered on and it works like a charm. 19.2 amp draw gives a voltage drop of 0.17volts across the MOSFET, with no appreciable heating! Back to work on more designs!