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Try 3 More Times

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If at first you don’t succeed… try at least three more times. :iconrarityfacehoofplz: It all goes back to the original problem:
Oh joy. Black, burnt, charred, and fried. by adamlhumphreys fav.me/d5kh0jh

It’s a photo comic, so it’s art right? :meow: For those that care or have any interest in the juicy technical details:

First I tried solid state. I knew there was a likeliness they probably wouldn’t work. I knew they were getting hot after the tub was nearly warm, but my dad was a bit more optimistic (and he is a Sr. systems engineer). But they weren’t burning in, they were burning out. Two failed short, and two went into thermal runaway. As you can see, the coupling capacitors burned up on all but one, but two technically still work. …They would’ve worked fine if they had a larger heat sink, or better yet, were water cooled by the tub water itself since ~102° F is still relatively low for a semiconductor. That would help heat the water, keep them cool, and be solid state all at the same time! :D But obviously that wasn’t an option for us not to mention we just wanted it to work.

Second I tried a 40A contactor relay. They should work great right? Well, except they were cheap trash! :rage: The element load is less than 25A. The contacts were obviously cheap because they built up resistance, got hot, and the bakelite that clamped them down broke. I figured it was particularly because of that initial brunt contact that took all the current, but a month and a half later, the first stage that didn’t take the brunt also failed. In short, don’t buy contactors from this guy: myworld.ebay.com/hvac-plus/ Verdict: You get what you pay for. :hmm:

Third/Fourth round: Mercury contactors (which are industrial grade) rated at 60A @ 480VAC. New contact points every time, and good for millions of cycles. They’re powering a 5000W heating element with 240VAC @ ~22A. In short, they should never fail and last for the rest of my life. :icontwilight-rapefaceplz: The only drawback is they have to be upright. Not a problem. :) Taking out one extra, (and unnecessary IMO since there’s another main power contactor in the controller box), stage for one side of the 240V line also wasn’t a big deal. Yay mercury! :dummy: (And if you think mercury in CLF bulbs are really that bad, read this: 1000bulbs.com/pages/mercury.ht… )

Next up: Humidity and temperature control for my dad’s greenhouse, at least after I get a nice mound going for it to sit on. The weather was so awesome today that I was able to make 8 wheel-barrels hauls! :w00t:
Image size
900x3428px 935.86 KB
Make
NIKON CORPORATION
Model
NIKON D5000
Shutter Speed
1/25 second
Aperture
F/8.0
Focal Length
32 mm
ISO Speed
800
Date Taken
Nov 14, 2012, 1:12:12 PM
© 2013 - 2024 adamlhumphreys
Comments11
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MisterJones4899's avatar
I visited this page a year ago !!

I know mercury wetted contactors are awesome, but MILLIONS of cycles is quite a claim for the solenoid part of it.

I'll have to research that....