The fireplace "fire light only" requires much less power, as it is only a series of light bulbs. The big juice comes from the electric heater.
The issue is that it is 120 VAC as Dave said and there is no way to separate the lights from the heater element electrically without rewiring inside the insert.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW