source for 50 amp ssr?

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runningweird

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so, I just melted a 40 amp ssr(my fault - heat sink was too small and no air moving within my panel)I also just installed the new electric line to my garage and now I am running much closer to true 50amp than I was at my last house which was just above 30.

I will be building a new panel soon to account for increased power and safety needs. I was looking for a source for 50 amp ssr's that aren't horribly expensive.

There are some on ebay for under 20 per that come with a heat sink, but there isn't even a manufacturer listed so I am a bit skeptical.
http://compare.ebay.com/like/400355508598?var=lv&ltyp=AllFixedPriceItemTypes&var=sbar


Crydom seem to be decent, thermo scientific make them but I don't want to pay 300 for a single ssr.

50 amp control panel, 2 5500w elements, HERMS
 
A single 5500w element draws 23a at 240v. Pardon my lack of knowledge, but why would you need an SSR that's greater than 40a? Are you running both elements from the same SSR? If so, I would instead split both elements and use 2 40A SSR's if possible. I know the Auber PID's can handle up to 5 SSR's in parallel.
 
A single 5500w element draws 23a at 240v. Pardon my lack of knowledge, but why would you need an SSR that's greater than 40a? Are you running both elements from the same SSR? If so, I would instead split both elements and use 2 40A SSR's if possible. I know the Auber PID's can handle up to 5 SSR's in parallel.

because I am dumb and forgot to do my math. no, both elements get their own ssr, I need to look for bigger heat sinks. thanks for setting me straight.
 
You don't need 50A, you just need a properly mounted heat sink and maybe a fan.

No-name Chinese SSRs are usually absolutely fine.
 
I had finally mounted all of my electric BK stuff in a small plastic box, rigging the SSR to be inside the box while the Heatsink was positioned outside for air circulation. Everythign was great and I shoveled the drive while it heated up. Got a great boil going and turned down the PWM.... Still boiling. Turned OFF the PWM circuit... Still boiling.

I shut off the breaker and it stopped. I discovered that the heat from the SSR had softened the plastic that I ran the screws through to the SSR, thereby loosening the contact between the heatsink and the SSR. Lesson learned.

Now that the circuit is tested, I'll have better luck once I mount it in a METAL box that won't give way a bit when warmed up.
 
Yo Dale. I can't even remember the name of my SSRs. Even if they had a name. :D
Hey Tom,
Mine all say 䨀椀洀椀 䠀攀渀搀爀椀砀, which I gotta believe means Crydom in Chinese.

Homercidal, am I reading right that you put heat sink compound on both sides of the plastic, between SSR and heat sink?

I was thinking of mounting mine with SSR on inside, and heat sink outside my metal box, but am worried about the thermal conductivity of the steel between the two.
 
Way too expensive! And shipping on top. For $19 I got 3x 40A Fotek's shipped. :p

Mr Natch, your idea will work fine with thermal compound on both surfaces. In fact the metal box itself might be enough of a heatsink.
 
Homercidal, am I reading right that you put heat sink compound on both sides of the plastic, between SSR and heat sink?

No, I cut an opening in the side of the box for the heatsink to fit into, with tabs of plastic so I could run screws through the tabs, into the SSR and thread into the heatsink. My heatsink was one of those cheap ones that come with the SSR and there was no way to mount the heatsink to the plastic and have it outside the box while the SSR was inside.

I thought I had a good solution until the heads of the screws sunk into the tabs a bit.

It's something I probably should have realized before I built it, but didn't. When I build my permanent control panel I'll do like Kal and use a large heatsink, no plastic required. I guess I was just in a hurry to test it out.
 
I've drilled holes in a big computer heatsink and screwed it on the back of an SSR, and mounted it so it stuck out the back of a plastic box. This worked because the back surface of the heatsink was slightly smaller than the back of the SSR.
 
I would not rely on your heatsink just being in open air to properly cool an SSR that is carrying 23A. Those bastards get HOT.

I always strongly recommend a fan to blow air across the heatsink.
 
WARNING!!!!

I used two Fotek 50 AMP SSR's for my HERMS with the heat sink on each individually with two computer fans blowing across them in my control box when I built mine. It worked perfectly for a year or so with bi-weekly brewing until the BK SSR began to sizzle and quickly start to arc inside the box on a brew day. I had to throw the breaker on the rig to shut it off and then blow out the flames. I would recommend you spend the extra money and buy a quality product and save yourself the subsequent time and money that I now have to put in to my system. If you decide to go the cheap way I would definitely put in thermal fuses mounted directly above the FOTEK's in case your not in the room when they blow or are too hammered to realize what's going on. :mug:
 
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