Melt Solid State Relay

[theblackxander]

Hey folks,

I have a MYPIN temp controller connected to a SSR-40DA that powers a two plug wall outlet. I usually have one heating element connected which has given me no problems but recently got a second element. I plugged that in today and noticed after running for an hour that my temp controller screen was flickering. I opened my box and saw that the SSR had melted.

Wondering if anyone has suggestions on how I should set this up so I can still use my 2 plug wall outlet. I basically want both elements to give off the same temperature.

 

[rusty_tlc]

How is the SSR heat sinked?
Assuming you have a properly rated heat sink the only way to increase the out put is to add another SSR, or find an SSR with a higher current rating.
With two elements both elements will never be exactly the same temp, the internal resistance will not be exactly matched so according to Ohm P=I^2R. In most cases that isn't important.

I strongly suggest you fuse the line inputs, occasionally an SSR will go into a "run away" state which is the result of the SCR (the thing inside that does the actual switching) latching.
The link below is a good style, I prefer to put the power switch on the front panel. The nice thing is power cords are easy to find .

http://www.jameco.com/webapp/wcs/st...roductId=265528&catalogId=10001&CID=CAT161PDF

 

[theblackxander]

Can you go into further detail about fusing the line inputs? I'm not sure what you mean by that.

 

[rusty_tlc]

Can you go into further detail about fusing the line inputs? I'm not sure what you mean by that.

.
Follow the link in my post. You need at least one fuse, preferably on the hot side, usually black in America. If the unit starts drawing to many amps the fuse blows and the unit shuts down.

 

[doug293cz]

.
Follow the link in my post. You need at least one fuse, preferably on the hot side, usually black in America. If the unit starts drawing to many amps the fuse blows and the unit shuts down.

I don't think fusing is the problem. More likely the SSR was overloaded (for the heatsinking available). or it was one of the many counterfeit SSR's on the market, which often use underrated components, and are prone to high failure rates (counterfeit Foteks are notorious for this.)

@theblackxander : What is the total wattage of both heaters you are trying to drive at the same time? Do you have pictures of the melted SSR? Shots from multiple angles are helpful for failure diagnosis.

Brew on

 

[rusty_tlc]

@doug293cz I was more thinking that there was no fuse which allowed an over current situation. Adding a fuse would be a preventive/safety measure.
These are the reasons I can think of for the melt down in descending order:
1- No heat sink, insufficient heat sink
2- Under rated SSR
3- Defective SSR

 

[doug293cz]

@doug293cz I was more thinking that there was no fuse which allowed an over current situation. Adding a fuse would be a preventive/safety measure.
These are the reasons I can think of for the melt down in descending order:
1- No heat sink, insufficient heat sink
2- Under rated SSR
3- Defective SSR

Unless there was a short downstream of the SSR, then an over current is unlikely to be the cause, since the elements will limit the current draw. It's possible that the current draw from two elements in parallel exceeded the rating of the control panel components, which is why I asked about total element power.

Brew on

 

[theblackxander]

View attachment ImageUploadedByHome Brew1482628805.695921.jpg

I did have a heat sink.

I know one element is 1200w. The other element I bought from brewmagic.com. They don't specify on their site what capacity the element is.


I was planning to buy a new ssr and wire two ssr to my system. I think the wall plug can have one connected to each socket.

I'm wondering if a fan in the box is necessary.

 

[rusty_tlc]

Unless there was a short downstream of the SSR, then an over current is unlikely to be the cause, since the elements will limit the current draw. It's possible that the current draw from two elements in parallel exceeded the rating of the control panel components, which is why I asked about total element power.

Brew on

Good points

 

[doug293cz]

View attachment 381741

I did have a heat sink.

I know one element is 1200w. The other element I bought from brewmagic.com. They don't specify on their site what capacity the element is.


I was planning to buy a new ssr and wire two ssr to my system. I think the wall plug can have one connected to each socket.

I'm wondering if a fan in the box is necessary.

Do you have an ohmmeter? If so, would you measure and report the resistance of the unknown element?

Normally, both wall receptacles in a duplex outlet are on the same breaker, meaning that you cannot plug a load near the circuit limit into both the the receptacles of a duplex outlet, without exceeding the circuit capacity. To use two high current loads, they have to be plugged into outlets that are on different breakers.

The SSR body looks like it was overheated internally, vs. overheated by by a loose, high resistance, terminal connection. So, either too much current for the SSR rating when both elements were powered, the SSR had insufficient heat sinking for the current draw (even tho it was within ratings), the current rating of the actual SSR was bogus (counterfeit SSR), or the SSR was defective (even if genuine.)

It looks like the heatsink on the SSR is inside the plastic panel enclosure. Is this actually the case? If so, that is pretty much the same as having no heatsink at all. The heatsink does not actually absorb much heat, but rather works to transfer the heat from its source to the ambient air. If the heatsink is inside a box of still air, there is very little heat transfer thru the heatsink.

A heatsink inside of an enclosure needs fan(s) that pull cool air from outside the enclosure, blows it across the heatsink (parallel to the fins), and exhausts the warmer air to outside the enclosure. Heatsinks mounted on the outside of the enclosure, without fan(s), and bonded thru a low thermal resistance interface to the SSR inside the enclosure, can provide adequate cooling depending on surface area and mounting orientation of the heatsink. Thermal management of higher power electronic devices is a complex field. There are people who devote entire careers to this. (I'm not one of them, but I worked with several.)
Brew on

 

[augiedoggy]

View attachment 381741

I did have a heat sink.

I know one element is 1200w. The other element I bought from brewmagic.com. They don't specify on their site what capacity the element is.


I was planning to buy a new ssr and wire two ssr to my system. I think the wall plug can have one connected to each socket.

I'm wondering if a fan in the box is necessary.

this is one of these..


https://www.alibaba.com/product-det...6085156.html?spm=a2700.7724838.0.0.qME6s4&s=p
they are not quality... they are the knockoff foteks its just recently the manufacturers changed the stickers so they no longer say fotek. Maybe fotek actually threatened them legally somehow I dont know but I saved that link above to my favorites about a month ago and they were pictured as knockoff foteks then.