Dum dum question about controlling 220V.

[np0x]

P = I / V

5000 = I / 220

I = 22.73 amps

To your question about ssr capacity, my understanding would be yes, there are 40 amp ssr's available out there as well as larger, while I haven't done it yet, my understanding is that you would put one on each leg(both are hot and both would be controlling 23 amps) and switch them with the same out# off of the bcs.

Additionally, i have done some testing and you will want some cooling, either active(fan) or passive(heat sink with fins) on the ssr's pulling the big amps, I have seen my ssr's get rather warm pulling only 13 amps through the 20 amp ssr's. Not cooling them will accelerate their eventual failure (everything eventually fails). :-/

[ECC]

23 amps on a 25amp SSR is really pushing it.

If you take a look at the datasheet (for example here from this thread), there are some Load Current Derating Curves. The actual maximum current is a function of the ambient temp, and base plate temp (therefore heatsink performance). Don't ask me to actually interpret those graphs, because they still confuse the hell out of me. But what they do tell me is that a 25 amp SSR may not necessarily handle 25 amps. And some sort of heatsink is a must, even if its just attaching the SSR directly to a metal enclosure.

[jmdenmark]

Follow-up question on this topic. I am planning to switch both hot legs using Out0 for the 220 feed for my 5500W HLT element as I have two D1240 SSRs (120V/40A) available. I noted most of the references use the 240V SSR (D24##).

As each individual leg of this circuit is only 110 and they don't get bridged up to 220V until the element I assume the 2 individual 120V SSRs will be fine, right?

Thanks,

Jim.