Brian-CHI (Customer) asked a question.
Heating Element modulation with GQ Series SSR Relay
I have a heating element that I don't want to slam on and off. Can I use a PWM, 0-10V, 4-20mA Signal from a controller to vary the output of a 4500W/240V heating element? More direct modulation basically.
What you describe is quite common. I suggest adding a shunt trip breaker upstream of the SSR to kill power to the heater in the even that the SSR fails shorted. Tie the shunt trip to a temperature controller that will trip the breaker if the temp sensor fails or hits a high alarm threshold.
Of course. circuit protection is always required for my projects
When you say; "modulation with GQ series SSR" do you mean the Gefran solid state relays sold by Automation Direct? If so, I took a quick look at the online store listing and didn't see any with an analog input. All I saw was discrete on/off units, those will not work as you want. Solid state relays with analog input and phase angle control output do exist and can be used for applications like yours. But they are not the most common thing (nor the cheapest) and with a quick look I didn't see any on AD's web site (but it was a quick look)
You can do PWM control with a discrete SSR, many of which have zero cross switching for AC loads. The resistive heating element "won't care" and the analog variety pretty much does the same thing, just moves the PWM logic to the SSR from the PLC.