Visitherm Heaters cycling?


Premium Member
I have a pair of 250 watt Visitherm heaters in my sump of my 125g reef tank. They are hooked up through a Digital Aquatics controller. I have the temp on my heaters set to 79 degrees and my controller is set to shut them down at 75 degrees.

I see this morning that my temperature is reading 73.5 degrees and that my heaters are not glowing lit. The Digital Aquatics controller is feeding them power; as it should, but the heaters are off.

Does anyone know if the heaters cycle on and off even though their internal thermostat is calling for heat to be on? I find it odd that both are off. When I touch the heaters they turn on for a few moments and then shut off.

I can't see the internal thermostat being 6 degrees off.

Any thoughts?