Although the heat function operates separately from the insert's flame or ember lights, it is not possible to have a completely dark fireplace while the heat on. The flame can be turned off, but other lights cannot. One of the requirements for certification through CSA/UL/ETL testing laboratories is that there should be a visible indication that the heater is on.
- In 18" models, the power switch that operates the heat function includes a red light. If the flame function is off, the red light on the heater's power switch will be the only light visible on the unit.
- In 23" and larger models with a log and ember bed, the ember bed will stay slightly aglow while the heat is in use. For these units, the fire/ember display can be cycled through by pressing the flame on the remote, L4 through L1. If the heat is on, there is an additional setting with even less lighting than L1.
- In 23" and larger models with crystals and side lights vary according to model, though all follow the rule that some light is present when the heat is on.