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-   -   Myth? SSRs fail in the CLOSED state? (http://www.homebrewtalk.com/f170/myth-ssrs-fail-closed-state-233541/)

Walker 03-20-2011 01:15 AM

Myth? SSRs fail in the CLOSED state?
 
I can't count the number of times I have seen the warning tossed around that SSRs often fail in the closed state, allowing current to flow unchecked. But, I've never actually seen anyone claim that it has happened to them, even after asking those on this forum if they have seen it happen.

A little voice in the back of my mind was wondering if this was another brewing boogeyman.... one of those things one person said one time, and then it just got repeated by everyone until it just became assumed truth. (like hot side aeration).

Well..... BEHOLD! I have the sinister beast in my possession :

http://www.homebrewtalk.com/gallery/...0/SSR_FAIL.jpg

I was going to brew tonight, and was taking advantage of the luxuries of automated temp control. My water was heating while I was bathing my kids and getting them ready for bed, and I was comfortable in the knowledge that my water would be perfectly heated and waiting for me whenever I eventually made it out to the garage to get rolling.

I happened to peek my head out to look at things and saw that the temp was 4 degrees over my set point and still rising. The PID was not attmepting to drive the heat.

I shut it down and returned to muck with it after the kids were in bed. Sure enough... the SSR is busted. It's passing current through no matter what.

Hammy71 03-20-2011 01:29 AM

Crimey, something else I feel compelled to buy a spare of now.

Walker 03-20-2011 01:32 AM

Yup. I just ordered two more online.

I have a friend who is slooooooooooooowly building his system and has two of them that he is not yet using, so I might swing by there tomorrow.

"Hey, neighbor, can I borrow a cup of sugar.... and 40A solid state relay?"

Bachhus 03-20-2011 01:42 AM

Wow, I kept reading about this being a posibility but geeesh. Do you have a failsafe built into your system and if not are you going to add one?

Mark

Walker 03-20-2011 01:49 AM

Quote:

Originally Posted by Bachhus (Post 2753113)
Wow, I kept reading about this being a posibility but geeesh. Do you have a failsafe built into your system and if not are you going to add one?

Mark

Yes, I have a failsafe wired up. I use a contactor as the master on/off for my element, and the contactor's control signal passes through a normaly closed "alarm" relay built into my PID. If the temp ever gets over 170*F, that alarm relay opens and the contator will shut off. (I caught the overheating before the failsafe kicked in tonight).

Theoretically, I could still be brewing tonight by flipping the PID into a different mode and using the contactor instead of the SSR for control, but that would be hard on the PID's built in relay and the contactor, so I ain't gonna do it.

gunner65 03-20-2011 01:54 AM

I had one fail "closed" that is when I added the light and the fan. Same exact ebay model as you are holding.

Walker 03-20-2011 01:57 AM

Quote:

Originally Posted by gunner65 (Post 2753150)
I had one fail "closed" that is when I added the light and the fan. Same exact ebay model as you are holding.

Yeah.... I've been dragging my feet on adding a fan to my panel. I've got two very small fans and intend to add one to blow air in and one to blow air out, but it's a drag to have to gut the system so that I can cut the holes in the thing, so it just hasn't happened yet.

I am considering going out to the garage and doing it tonight, though. :D

Bachhus 03-20-2011 05:39 AM

Quote:

Originally Posted by Walker (Post 2753133)
Yes, I have a failsafe wired up. I use a contactor as the master on/off for my element, and the contactor's control signal passes through a normaly closed "alarm" relay built into my PID. If the temp ever gets over 170*F, that alarm relay opens and the contator will shut off. (I caught the overheating before the failsafe kicked in tonight).

Theoretically, I could still be brewing tonight by flipping the PID into a different mode and using the contactor instead of the SSR for control, but that would be hard on the PID's built in relay and the contactor, so I ain't gonna do it.

That sounds like a good way to do it. Which contactor are you using?
Mark

konrad 03-20-2011 06:32 AM

How much usage did you get out of your failed SSR?

Walker 03-20-2011 12:43 PM

Quote:

Originally Posted by Bachhus (Post 2753565)
That sounds like a good way to do it. Which contactor are you using?
Mark

Just one I found on ebay for a heck of a deal. 40A load, 120V coil. Got it for like $8 and some change. The brand is Smart Electric.

Quote:

Originally Posted by konrad (Post 2753618)
How much usage did you get out of your failed SSR?

Electric system went live almost a year ago, so maybe a little less than 20 batches. Oh, and a few multi-day sous vide cooking sessions, too.

The SSR was only $8, give or take a dollar, so I definitely got my money's worth out of the thing. It just sucks to have to replace it and have a brew night nipped in the bud.


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