I'll need about 6 amps per channel for an upcoming project, and I was wondering if there's any reason not to replace the standard SSR4 triacs with a higher rating as long as I provide enough heat sinking and I double up the PCB traces with wire where necessary. The other possibility I've considered is to double the number of triacs by running them in parallel. I know that the load will never completely balance (I've seen that in paralleled mosfets), but even if it's 25% / 75%, it shouldn't exceed the rating. If thermal runaway is a problem, maybe I could add some components to handle that.
"and I was wondering if there's any reason"
Yes there are a whole lot of reasons why you can not and should not do this. First it is a fire hazard. There is not room to get rid of that much heat in the SSR4 even if you had a heatsink that could. You would be putting the equivilent of a 40 watt light bulb in that case. It will get too hot.
There are a whole lot of other reasons this is a bad idea and not safe. Can I suggest that instead of spending all that money to make something I would worry would burn your house down you simply use this instead :
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LoginNotice that even as large as it is it is limited to its dissipation but it does get you almost where you need to be. They also are limited because while you want to control 24 amps the standard circuits can only deliver 15 amps so how are you going to feed that much current to a ssr4. Then there is the connectors on the board that are not rated for anywhere near those current levels.
The SSR4 is limited to 1 amp per channel without a heatsink and 2 amps with it for good reasons. This is not a triac issue but heat dissipation/traces/connector rating/safety issue. 6 amps a channel is not running a little over safe it would be way outside the safe range on this controller.
Use a couple of them and split your lights up, or use a commercial controller. I can' t afford to have people getting hurt with my stuff it would take all the fun out of it for me.
RJ