1 x 3 phase SSR vs 3 x single phase SSRs

Thread Starter


Joined Nov 27, 2013
Hi guys,

Is there a reason why I can't use 3 x single phase SSRs (with an appropriate rating of course) with their "coil" sides in parallel to switch a bank of resistive heating elements in lieu of a single 3 phase SSR?

I'm reviewing an old circuit which was terribly un-balanced - anyway, the circuit is now fine, but budget is a factor (as is resistance to change by those building it, but that's another story). A single 3 phase SSR is expensive, but three of the single phase SSRs that they already use would (I think) do the job just as well at a fraction of the cost.

I can't think of any reasons why it would be a problem, but I have found it is always best to check.

Thanks in advance for any help you are able to offer,

...and merry Christmas



Joined Jan 15, 2015
You may want to give this a read. Pay attention around page 26 where a Two Leg SCR Power Control is used in a 3 phase application. Overall the Chromolox link is a good read on controlling heaters, While I don't know what your actual load is prior to retiring I used the two leg method on some autoclave loads averaging 432 KW (72 heater bands split 3 KW per side) and it worked out great.