Spectacular solid state relay failure

I wired up a solid state relay to only turn on the hot water tank when electricity is cheapest. Using a 25 amp relay to switch about 22 amperes. I guess that was too close to it's rating. No issue for 4 months, then failed spectacularly.

My previous video of this set-up:

"bigclivedotcom" has done a teardown and analysis of one of these:

[jeremyturner]

It decided to become a plasma state relay.

[Firstner]

at least you had a house to sell after this

[Petertronic]

A comment from the original video said: "The fakes do have a bad habit of catching fire."

[davidchuang]

This is an application where a standard mechanical relay would be better. A SSW is more suited to situations where the load needs to be switched on/off rapidly or in short intervals, such as in the case of a PID controlled heater application. If the point was to maintain the tank temperature within a very narrow range at all times, then an SSR with a PID controller would be ideal. However, in this example, since the system is either on or off for long periods of time, a stout mechanical relay with any suitable coil voltage would have been more than adequate.

[Therapistinthewhitehouse]

So glad you and your family weren’t hurt. Best wishes from Britain.

[douglanglois]

Kudos to you for publicizing the failure, and not just brushing it under the carpet.

But I guess the "safety know-it-alls" have a point sometimes, eh?

[yamazakirichard]

Thanks for posting your failures for us to learn from. This is something I have wanted to try myself but won't.

[ZenMuffn]

wow. you're brave. I usually don't go over 2/3 of what the spec sheet says something like this can take.

[MazeFrame]

TO-220 is not a lot of surface to sink away the heat.
After one of those blew in a setup, I bolted the next one to an old Intel heatsink (one of those with copper core) and that fixed it.

[Havreflan]

The safety-know-it-alls saw this coming. You got lucky.

[fps]

Best part of your channel is showing and analyzing when things go wrong. Hope your insurance agent is not a subscriber.

[SuperGrover]

I've never had luck with the solid state relays in those situations. Good old school oversized mechanical contactors for the win...

[treynamy]

Thank you for this Matthias. I did a similar installation on two water heaters in remote locations using contactors like you'd find on an air conditioning unit. Less susceptible to heat issues I think. I paid about $10 each on Amazon, and they had 24v, 110v and 240v activation inputs for the contactor. But, this video makes me want to turn them on while at room temp and monitor the temps at all the connection points. Thanks!

[marcsimonsen]

Loved the teardown and forensics! Looking forward to the direction you are taking us!

[yorgle]

I've found that spraying some isopropyl/rubbing alcohol on charred boards like that and a light scrub with a toothbrush makes it much easier to see what's happened after events like this. :}

[gardnmi]

Let's hope the folks that watched the first video and implemented your idea see this video too.

Reading the comments in the original video someone mentioned that these knockoffs tend to catch fire....lol.

[RadioactiveOwl]

So glad you're still doing videos despite your tendinitis :)

[roldac]

Good job on diagnosing this potential fire hazzard Fire Marshall Wandel. I set up my solid state relay with a cooling fan but will monitor it closer for potential failure.

[x_phl]

I've disassembled bunch of those solid state relays from different ebay sellers and found that 100% of triacs are grossly underpowered (12 - 16A, while relay is rated for 25A) and some of the relays had clearance issues, meaning that if some surge condition would happen - the relay will disintegrate, just like yours did. My advice - don't use those cheap SSRs from ebay, buy them from Digikey, Mouser, etc. (yes, they will be much more expensive).

[stefantrethan]

I'm just glad that deathtrap is gone and nobody got hurt, you were lucky the fire didn't spread.
If you look at the size of the heatsinks that come optional with these relays to achieve their full rating (well, not the chinese ones but proper ones) you know why this was bound to fail.