Killing SSR (relays) - Need to understand

[jwest7788]

Attached pic of dead SSR innards.

To answer questions since my last post.

The grease is thermal compound between the SSR and the heatsink (CPU thermal compound to be precise) --> Eliminating a gap between the SSR and heatsink, I actually used my milling machine to take a few thousands of an inch off the bottom of the SSR and top of the heat sink to ensure it was perfectly flush fit, added thermal compound to be sure.

In the pic provided, the hose clamps are holding on the (low voltage) wires to the thermocouple, temporary solutions while I figured out something more permenant. (The thermocouple is super thick, like twice as thick as a coathanger, haha)

In that pic the SSR is no longer hooked up, but the green wire at the bottom usually goes to the open end of the SSR, and of course SSR on the heat sink.

Fan on all the time SSR still got too hot.




Here a thought, two SSR's, one per heating element --> if done right should take some of the strain off both SSRs?

 

[dorke]

About the heat issue:

1. Looking at the fan vs. the heat-sink location it is clear that most air blown by the fan doesn't go through the fins,
it therefore will not cool the SSR very efficiently.That needs to be corrected.

2. If possible I would take the fan +SSR+haetsink outside of the casing (wiring the AC only to the heaters),
thinking the ambient temperature would be much lower that way than the way it is now ,close to the heaters.

 

[jwest7788]

Just an update for everyone.

Firstly, I'm an idiot.

Secondly, I've learned from someone who knows what they're doing, that when two 30amp breakers are connected, even though they are marked as "30" they are indeed now a 60 amp breaker.

I've been using under sized SSR relays for the actual max load of the Kiln.

SSR 80Amp on order now.

 

[Minder]

[QUOTE="jwest7788, post: 1693105, member: 43561"
Secondly, I've learned from someone who knows what they're doing, that when two 30amp breakers are connected, even though they are marked as "30" they are indeed now a 60 amp breaker.

.[/QUOTE]
Doesn't quite make any sense!!?
If you are in N.A. then if you want 30amp 240v protection then a double 30amp breaker is used.
They are still 30amp, likewise you would need a double 60amp for a 60amp load.
The breakers are essentially each in series with the load, just one in each live leg.
M.

 

[Y2KEDDIE]

You would have more reliability if you use Power Contactors (Power Relays) to apply power to the heating elements. You can use the SS relays to activate the coils of the Contactors.

I use a similar circuit to operate an air dryer for an air power system. The temperature controller has a J thermocouple connected ,which measures the temperature of the alternate desiccant tower during the baking cycle. When the thermocouple senses a preset temperature the controller module turns off it's associated contactor via a Solid State Relay.
Even in an industrial setting such as described, I had the SS relays fail, but hardly ever the contactor fails.