What just happened?

[Chrisde]

So I finally got all on my equipment together and ran the auto tune for my pid which went fine (I think, temp held at 154 when set at 150 for almost an hour but felt hotter to touch than 154 so I will get thermo tomorrow to test it against).

I put it in manual mode to bring to boil. Around 200F I smelled burning plastic. I went to the box to shut off power (didn't wanna touch controller at this time) and something popped loud. Inspected box and element switch was melted and ssr exploded. I touched ssr and heatsink and they weren't even slightly warm.

5500w element
40a ssr
25a dpst switch

Why would the switch melt?

Did the ssr explode because switch shorted?

 

[BrunDog]

Need a schematic.

-BD

 

[Chrisde]

Need a schematic.

-BD

Don't have one drawn but extremely simple

4 wire from box 30a breaker into 50a spa panel. From spa panel

Hot: ssr to switch to outlet
Hot: split to pid... other to switch then outlet
White: pid
Ground: outlet

 

[Chrisde]

Anyone?

 

[RufusBrewer]

The switch melted because too much current went through it. If the switch is rated for 220 VAC and 30 Amps, it should have been OK,

The SSR did not explode because the switch melted? This assumes you wired it Power Source -> Switch -> SSR. If the switch failed and the failure cuased a short, then the SSR could have exceeded it's current capacity.

It would not occur to me to put a SSR before s DPDT mechanical switch. Does the SSR have some sort of PWM?

You problem is a design error or an equipment failure. Or a design error than induced an equipment failure.

Not a lot of help, but if you used components that the rating exceed the ratings of the breaker feeding them, the breaker should have tripped before the components failed. At least in a broad stroke conceptual sense.

 

[jeffmeh]

It would be much easier to help if you supplied a drawing, even a crude one.

 

[Chrisde]

Black and red are hots
Blue neutral
Green ground

Not sure 3 and 4 in drawing to ssr r correct but they r in the system. + to + and - to -

Hope this helps.

View attachment 1433607166225.jpg

 

[augiedoggy]

The switch melted because too much current went through it. If the switch is rated for 220 VAC and 30 Amps, it should have been OK,

The SSR did not explode because the switch melted? This assumes you wired it Power Source -> Switch -> SSR. If the switch failed and the failure cuased a short, then the SSR could have exceeded it's current capacity.

It would not occur to me to put a SSR before s DPDT mechanical switch. Does the SSR have some sort of PWM?

You problem is a design error or an equipment failure. Or a design error than induced an equipment failure.

Not a lot of help, but if you used components that the rating exceed the ratings of the breaker feeding them, the breaker should have tripped before the components failed. At least in a broad stroke conceptual sense.

last time I checked a 5500w 240v element only draws 23a max...which is less than the switches 25a rating so I am failing to see where you got this conclusion?

to the op your diagram looks sound...I would guess that something is or was defective and caused your failure...

Or... Are you absolutely sure you wired the switch in correctly and didnt cross wire the hot leads?? That would do it... easy to check with a meter. If I where a betting man I would say thats what you did...
if its a dual pole houshold switch the left and right sides operate as two independent switches not top and bottom.

 

[Chrisde]

last time I checked a 5500w 240v element only draws 23a max...which is less than the switches 25a rating so I am failing to see where you got this conclusion?

to the op your diagram looks sound...I would guess that something is or was defective and caused your failure...

Or... Are you absolutely sure you wired the switch in correctly and didnt cross wire the hot leads?? That would do it... easy to check with a meter. If I where a betting man I would say thats what you did...
if its a dual pole houshold switch the left and right sides operate as two independent switches not top and bottom.

I am hoping this is what it is. It wasn't a household switch it was a cheap toggle with rubber boot. Just replaced with 30 2 pole house type switch. Line in connected to bottom 2 screws. Load out connected to top 2. Here we go again. Unfortunately I only have a 25a ssr on hand. This will get replaced soon but should work with the fan I have.

Thank you. Here we go again.

 

[augiedoggy]

I am hoping this is what it is. It wasn't a household switch it was a cheap toggle with rubber boot. Just replaced with 30 2 pole house type switch. Line in connected to bottom 2 screws. Load out connected to top 2. Here we go again. Unfortunately I only have a 25a ssr on hand. This will get replaced soon but should work with the fan I have.

Thank you. Here we go again.

25A ssr is perfectly safe to use... a 5500w element draws 22-23a... if you use a meter you can see which teminals on the switch go together... why guess? its dangerous and expensive...

 

[RufusBrewer]

last time I checked a 5500w 240v element only draws 23a max...which is less than the switches 25a rating so I am failing to see where you got this conclusion?

to the op your diagram looks sound...I would guess that something is or was defective and caused your failure...

Or... Are you absolutely sure you wired the switch in correctly and didnt cross wire the hot leads?? That would do it... easy to check with a meter. If I where a betting man I would say thats what you did...
if its a dual pole houshold switch the left and right sides operate as two independent switches not top and bottom.

Why else would a switch fail/melt other than excessive current? I guess excessive voltage would do it, but given the design, that is highly unlikely.

What logical and likely explanation do you have for his switch melting, other than my dumb ass conclusion.?

Is it impossible for a heating element to fail in such a way that it draws more than the rated current? Is it possible something got between two terminals and caused excessive current draw? What about leaks and water/wort getting into some place that is supposed to be dry?

One thing that strikes me is that this failure happened well into his brew session.

Looking at his drawing, any mistake in wiring would cause a significant short and a nearly instant failure. Perhaps I overlooked something. It strikes me as odd that it was running properly long enough to heat to 200 deg F. Then he smelled smoke, turned it off and then the pop.

My gut tells me a component failure. Component failure due being a defective component or operation beyond specifications.

 

[doug293cz]

... it was a cheap toggle with rubber boot. ...

Thank you. Here we go again.

Can you post the mfg & PN for the toggle switch? I have looked for double pole switches with 25 - 30A ratings, and all of the inexpensive toggles that claim those kinds of current ratings, only claim them for low DC voltages, and are rated much lower when used at 240V. I suspect that you may have misread the switches specs, or they may have been incomplete, and that your application was actually well outside of the switches rating. If the switch shorted line1 to line2 when it failed, then with your design, it would have greatly exceeded the SSR's current rating, causing it fail very quickly (and likely with a pop.)

Edit: It's also possible that the connections to the switch may not have been constructed well enough, and had too high a resistance. This could cause the connections to heat up, eventually destroying the switch.
Brew on

 

[Bobby_M]

Agree with above. I have never seen a compact toggle rated for 25a at 240v.

 

[jsguitar]

When the OP says 'cheap' I'm not sure how cheap we're talking about, but there are small toggle switches like the NKK high capacity S series that are rated at 30A/250V (resistive).

http://www.nkkswitches.com/pdf/stoggleshighcap.pdf

I use one of these, but some switches have a considerably lower amp rating at 250v than at 120V.

As mentioned, we need the exact details of the switch from the OP to know for sure if the rating was an issue.

 

[doug293cz]

When the OP says 'cheap' I'm not sure how cheap we're talking about, but there are small toggle switches like the NKK high capacity S series that are rated at 30A/250V (resistive).

http://www.nkkswitches.com/pdf/stoggleshighcap.pdf

I use one of these, but some switches have a considerably lower amp rating at 250v than at 120V.

As mentioned, we need the exact details of the switch from the OP to know for sure if the rating was an issue.

Thanks for the reference. Those switches look like they are rated appropriately (some of them.)

Brew on

 

[Chrisde]

http://m.ebay.com/itm/231326605882?_mwBanner=1

Here is the switch I had. It was probably running for 1.5 hours before this happened.

 

[doug293cz]

http://m.ebay.com/itm/231326605882?_mwBanner=1

Here is the switch I had. It was probably running for 1.5 hours before this happened.

That switch appears to have an adequate rating. So, either the switch had a defect, or the connections to the switch had excess resistance. Do you have any clear pictures of the failed switch?

Brew on

 

[RufusBrewer]

Where is a theorectical possibilty, just throwing out a spit ball on this one.

If you are using a PWM and a SSR, you are making some square waves that are high frequency compared to 50-60 hz sine waves. At 220 VAC there is could be some serious enegry switching and flying around in the switch. How reactive (capacitance or inductive) is a heating element? If it has any reactance at all, you got charging and discharging into that switch.

One thing that might help my hypotheictal situation is put the SSR between the switch and and the heating element. Use the SSR as a buffer.

 

[augiedoggy]

I didnt realize it was working for a while before the meltdown... What size wire and what type of connectors did you use?

 

[Chrisde]

I didnt realize it was working for a while before the meltdown... What size wire and what type of connectors did you use?

10g wire and the little fork connectors. I am not using connectors for this switch since the wire plugs into outlet.

After replacing the ssr and switch yesterday I ran a test session with just water (45 min mash hour boil) and everything went fine. Then I made an actual batch and it went great. My efficiency sucked but I think that's because the hole in the bag are too small.

I am thinking it may have just been a bad switch. Or... I did have the leads and loads mixed up.

 

[doug293cz]

Congrats on a successful brew session with your new controller!

I'd recommend that you examine the switch carefully after each brew session for signs of damage. If you see anything that looks like minor melting or discoloration, you should probably replace the switch with something more robust.

10g wire and the little fork connectors. I am not using connectors for this switch since the wire plugs into outlet.

That switch has screw terminals. Why aren't you using spade connectors on it? And, what do you mean by "plugs into outlet"? Doesn't make sense to me in this context.

I am thinking it may have just been a bad switch. Or... I did have the leads and loads mixed up.

Bad switch is a definite possibility. If leads were mixed up, it would have blown up in milliseconds after powering up, not run for more than an hour first. I'd still like to see pics of the failed switch, especially focused on the terminals.

My efficiency sucked but I think that's because the hole in the bag are too small.

I doubt that the low efficiency was due to a tight weave of the bag cloth. For guidelines on diagnosing efficiency problems, look at my post here: https://www.homebrewtalk.com/showpost.php?p=6914382&postcount=13

Brew on

 

[Chrisde]

Here r some pics. First is the new switch. Sorry, the "plugs into outlet" should have been plugs into switch. The new switch has holds in the back for the wire. Insert wire and tighten screw. No connector needed.

One of the connectors I used is still on the old switch. Hope these help.

View attachment 1433701047268.jpg

View attachment 1433701058457.jpg

View attachment 1433701074168.jpg

View attachment 1433701086091.jpg

 

[doug293cz]

Ok, didn't realize you changed switch models. I think the new one will give you better service.

The pics are quite helpful from a failure analysis perspective. Looks like the switch failed internally, as there is no evidence of overheating of the terminals. But, it definitely looks like the internal contacts heated up and actually melted thru the housing.

Brew on

 

[augiedoggy]

Ok, didn't realize you changed switch models. I think the new one will give you better service.

The pics are quite helpful from a failure analysis perspective. Looks like the switch failed internally, as there is no evidence of overheating of the terminals. But, it definitely looks like the internal contacts heated up and actually melted thru the housing.

Brew on

I agree... and I had made the comment about the switch being wired wrong before I realized that it worked for a period of time.