Like I've mentioned in the previous testing of the industrial heater unit STEGO CS028 400Watt (230V) I'd like to test the ability to control the heater unit with a TRIAC Dimmer. The heater unit consists of a normal 230V Fan and a PTC heater. The fan is easy to control however I'm not sure about the ptc element heater. Maybe I'll face some frequency problems 

TRIAC-Dimmer:

For controlling the AC fan and the AC ptc element I've ordered the TRIAC-Dimmer from RobotDyn.

Test-Setup:

First you'll have to separate the ptc element and the fan. Originally the two elements are wired together (Weco connector) so both run of the same power source. 

The fan and the ptc heater are then connected to the RobotDyn 2Channel AC-Dimmer. We're talking about mains voltage (230V!) so keep that in mind and in case of doubt please check back with an electrician or abort. 

Controlling the TRIAC-Dimmer:

For controlling the TRIAC-Dimmer I'm using an arduino Nano and connected the pins as following:

• VCC to +5V (Nano)
• GND to GND (Nano)
• Zero to D2 (Nano) -> Zerocrossing pin
• DMR1 to D11 (Nano)
• DMR2 to D12 (Nano)

RobotDyn published a library for this TRIAC-Dimmer and can be found on (https://github.com/RobotDynOfficial/RBDDimmer) therefore the implementation is quite simpel. 

Results/Experience:

The controlling of the 230V fan works just fine. I'm able to control the speed and even turn off the fan. I've measured the voltage and noticed that the fan starts spinning at 30% (which equals 111V) and reaches the max speed at approx. 65% (which equals 229V). If you increase the speed even more the fan will begin to stall. Because of this ''strange'' range of 30 to 65% you can use the map function to adjust these values. Something like map(fan, 0, 100, 30, 65).

The problem:

When I try to control the ptc element as well suddenly I can no longer control the fan speed. The fan just stalls independent of the value (30 to 65%). I even switched the connectors on the mains side to check if the TRIAC-Dimmer is fully functional. The fan standalone works in both ways and quickly starts to stall I've a try to use the ptc element parallel. I noticed that the element gets warm so maybe there isn't enough capacity available for heating AND the fan. Or maybe that's because of the characeristics of this ptc elements? If you have an idea I'd love to hear from you in the comments. 

I will investigate this behaviour in the near future and keep you updated.