My SSR exploded - can anyone help troubleshoot?

[Geordan]

Hey folks, I just finished putting together my full electric control panel last night, and it's perfect except for a (pretty big) snag. I've wired my BK control up using a Potentiometer and an AC control SSR; when I turned it on, it worked great, and it heated REALLY fast -- I got 5.5g from 50f to 160f using my 5500 element in 10 minutes. A few minutes later, just as a I was about to hit a boil, I heard a loud "pop" and smoke starting leaking out from the panel.

The SSR itself had gone poof -- distorted, melted, and the inside is completely charred black -- easy to see this since the popping noise was the front plate piece popping off.

All connections are tight, wires are correctly sized, and there's no evidence of burning or charring anywhere else but the inside of the SSR itself. What puzzles me is what would have caused it to burn up; it's a 40A SSR with a load that's only 22A or so.

Does anyone have any thoughts or aha moments that come to mind?

 

[brew_ny]

do you have a heat sink on it ?and does it get good air flow ?

all the best

S_M

 

[Geordan]

Yup, mounted on a heatsink, decent airflow.

 

[sandyeggoxj]

Do you have thermal paste between the SSR and the heatsink?

 

[Geordan]

Nope, installed as they came, no thermal paste.

 

[sandyeggoxj]

Nope, installed as they came, no thermal paste.

Go to radioshack and get some thermal past. I always install the paste. You will notice that the mounting surfaces are not flat. The paste fills the gaps so that you get full contact and move as much heat as possible to the heatsink. You probably just overheated the relay because it had little contact with the heatsink, essentially it did not have a heatsink installed.

 

[Deece]

Pics? I have noticed there are some eagle eyes here that are pretty good at spotting miss wired panels.

 

[atoughram]

What brand of SSR? Ebay Fotek by chance? 25A? 40A?

Thermal Paste is a good suggestion for that big of an element.

It's a good sign that it worked for at least 10 minutes.

 

[thekraken]

Go to radioshack and get some thermal past. I always install the paste. You will notice that the mounting surfaces are not flat. The paste fills the gaps so that you get full contact and move as much heat as possible to the heatsink. You probably just overheated the relay because it had little contact with the heatsink, essentially it did not have a heatsink installed.

Any one ever lapped their ssr or is that an unnecessary waste of time?

 

[doug293cz]

A fail with popping sound indicates that the SSR heated up very hot, very rapidly. Doesn't sound like a fail due to just running over temp. And since it ran for 10 minutes before failing all of a sudden, it's not likely that a wiring error caused the problem. There may have been a manufacturing defect inside the SSR that led to the early life fail. Early life fails are what manufacturers' warranties are intended to cover. If the seller offered a warranty, you should ask for a replacement.

Brew on

 

[doug293cz]

Any one ever lapped their ssr or is that an unnecessary waste of time?

It's likely to be a waste of time, as the device and/or heatsink are likely to deform when hot, so that the benefit of lapping is diminished or eliminated.

For heatsink compound, less is usually better. You want to have the thinnest layer that will completely fill any gaps between the component and heatsink, since the thicker the layer, the less well it conducts heat between the source and the sink. You also want to eliminate any bubbles/voids in the compound film, as these will also reduce the amount of heat conducted across the layer.

Brew on

 

[jleiii]

I've wired my BK control up using a Potentiometer and an AC control SSR;

This may sound like splitting hairs, but is it an SSR or an SSVR, and wired accordingly? Not sure an SSR would even work with a potentiometer no matter how it's wired.

 

[processhead]

It's likely to be a waste of time, as the device and/or heatsink are likely to deform when hot, so that the benefit of lapping is diminished or eliminated.

For heatsink compound, less is usually better. You want to have the thinnest layer that will completely fill any gaps between the component and heatsink, since the thicker the layer, the less well it conducts heat between the source and the sink. You also want to eliminate any bubbles/voids in the compound film, as these will also reduce the amount of heat conducted across the layer.

Brew on

It is almost impossible to put too much heat sink paste on a properly mounted SSR.

If its mounted correctly, the SSR will make full-surface contact with the heat sink. If you have this condition, any excess compound will be squeezed out around the edges.

If either the heat sink or the SSR has an irregular surface or high spots, you won't get the full surface contact needed to achieve proper heat transfer.

Fortunately, most manufacturers do a pretty good job of making sure those surfaces are smooth and flat.

From your description, it sounds like your device suffered premature failure.
Be sure to mount the replacement as-above with heat sink compound, and it should be fine.

 

[rudylyon57]

Hey folks, I just finished putting together my full electric control panel last night, and it's perfect except for a (pretty big) snag. I've wired my BK control up using a Potentiometer and an AC control SSR; when I turned it on, it worked great, and it heated REALLY fast -- I got 5.5g from 50f to 160f using my 5500 element in 10 minutes. A few minutes later, just as a I was about to hit a boil, I heard a loud "pop" and smoke starting leaking out from the panel.

The SSR itself had gone poof -- distorted, melted, and the inside is completely charred black -- easy to see this since the popping noise was the front plate piece popping off.

All connections are tight, wires are correctly sized, and there's no evidence of burning or charring anywhere else but the inside of the SSR itself. What puzzles me is what would have caused it to burn up; it's a 40A SSR with a load that's only 22A or so.

Does anyone have any thoughts or aha moments that come to mind?

One thing you said about your SSR is intriguing,"I've wired my BK control up using a Potentiometer and an AC control SSR". I'm not an expert by any means but can you control an SSR with variable voltage AC as a means for regulating power? If my hunch is correct, is it possible switching at 60 hz may have damaged the SSR?

 

[timpoulsen]

Were you using a SSVR or a SSR? If you put a pot on a solid state relay instead of a solid state voltage regulator that may be your problem.

 

[doug293cz]

Do you have a schematic and parts list you can post for us. Might provide insight into possible failure modes.

Brew on

 

[jleiii]

3 of us have now questioned the SSR vs SSVR point and no reply from the OP.
Geordan, are you still following this thread?

 

[doug293cz]

3 of us have now questioned the SSR vs SSVR point and no reply from the OP.
Geordan, are you still following this thread?

Hooking a potentiometer up to a SSR would provide no way to ever turn the SSR on, but would also not cause it to fail. Since he got it to function for a short while, it must have been a SSVR, or there was some PWM circuitry between the pot and an SSR.

Brew on

 

[Geordan]

Sorry folks, ended up having to deal with an emergency just after posting this (unrelated) and it totally slipped my mind that I'd posted it.

I'm using an SSR controlled via a potentiometer (this type: http://www.ebay.ca/itm/1pcs-Solid-S...589?pt=LH_DefaultDomain_0&hash=item27e4fccdf5). Ended up replacing the SSR with a new one and it works perfectly fine, so anyone who guessed "Faulty POS ebay SSR" is the winner in this one!

 

[atoughram]

This is the one I bought and it's worked well so far

http://www.ebay.com/itm/1pc-KYOTTO-...193?pt=LH_DefaultDomain_0&hash=item20b9ab9ca9

I've got it on a heat sink with a fan and it puts off some heat while driving a 5500W element.

 

[processhead]

This is the one I bought and it's worked well so far

http://www.ebay.com/itm/1pc-KYOTTO-A...item20b9ab9ca9

I've got it on a heat sink with a fan and it puts off some heat while driving a 5500W element.

That's SSR is rated for 25 amps, and if it is working for you that's great.

While 25 amps is above the maximum amp draw for a 5500 watt element, its not by much.

Personally, I would want a little more head-room so you have some safety factor at full output.

I am using an SSR rated at 40 amps with the 5500 watt element on my system.

 

[rudylyon57]

Sorry folks, ended up having to deal with an emergency just after posting this (unrelated) and it totally slipped my mind that I'd posted it.

I'm using an SSR controlled via a potentiometer (this type: http://www.ebay.ca/itm/1pcs-Solid-S...589?pt=LH_DefaultDomain_0&hash=item27e4fccdf5). Ended up replacing the SSR with a new one and it works perfectly fine, so anyone who guessed "Faulty POS ebay SSR" is the winner in this one!

I'll be using something similar so my fingers are crossed! I think this device is also referred to as an SSVR. Glad to hear its working well now.

 

[atoughram]

That's SSR is rated for 25 amps, and if it is working for you that's great.

While 25 amps is above the maximum amp draw for a 5500 watt element, its not by much.

Personally, I would want a little more head-room so you have some safety factor at full output.

I am using an SSR rated at 40 amps with the 5500 watt element on my system.

I'm sorry - you are correct - the one I bought is a 40a Kyotto. "1pc KYOTTO AC Solid State Relay SSR KR2040AX 280VAC 40A"

 

[augiedoggy]

OK I believe I see the issue here.... this is another case of lack of knowledge being blamed on an inexpensive product.

The truth is you can't use a potentiometer with a regular SSR like the first one you linked. You need an ssrv They are different.... the ssrv stands for variable resistance and the potentiometer is what controls varying that resistance. You can use a pwm controller on an ssr but not a potentiometer I'm glad you came back to fill us in... if I had a nickel for every time someone blames lack of doing their homework on a cheap product I'd have blichmann kettles.... The reality is if its expensive people tend to pay more attention to the details...

 

[doug293cz]

I actually bought a kyotto ssvr they sell with a potentiometer included.. I wasn't aware that a standard ssr was designed to work with a potentiometer
Edit I just saw your link....that's an ssrv you bought the last time around so it would work unlike an ssr .am I wrong in guessing you might have bought a regular SSR the first time? I know everyone likes to blame failures on cheap components or "eBay" so please post a link to the type and brand you used the first time... Its helps weed out the mistakes from the actual defective or crap products.

A "standard" SSR needs a voltage input with some limited current sourcing capability. This is because the inputs turn on an LED that is used to trigger a photodiode that actually turns on the triac. A potentiometer cannot turn on an LED. An SSVR uses a potentiometer to control PWM circuitry within the SSVR that turns on the triac. In both cases the high current switching is handled by a triac.

Since the OP had the circuit working for a short while with a potentiometer, he had to have (which he later confirmed) an SSVR. So his failure was almost certainly due to a weak component (likely a manufacturing defect.)

Brew on

 

[augiedoggy]

A "standard" SSR needs a voltage input with some limited current sourcing capability. This is because the inputs turn on an LED that is used to trigger a photodiode that actually turns on the triac. A potentiometer cannot turn on an LED. An SSVR uses a potentiometer to control PWM circuitry within the SSVR that turns on the triac. In both cases the high current switching is handled by a triac.

Since the OP had the circuit working for a short while with a potentiometer, he had to have (which he later confirmed) an SSVR. So his failure was almost certainly due to a weak component (likely a manufacturing defect.)

Brew on

Edit **
after looking over the fotek link again I see that I am wrong and this does appear to be a case of a defective product... This is the first time I saw a knockoff of the fotek ssvrs on eBay... the fact that the label just states ssr on the sticker threw me off...