New multiplus 3 k inverter installation. MPPT solar, Touch 50 and cerbo GX. Very pleased with the install done by SESindiana.com. I notice that when on shore power, and system switches to bulk charging only (inverter off) the system warms up and internal fan turns on. It becomes much warmer than when it is simply running inverter on and charging from solar input. Any thoughts? Is this normal, and if so, why?