Attempting to find a manual for a Heart inverter can be tough. Some of the Heart inverter/chargers required a plug-in remote panel to turn off the charger function. Others did have a charger switch on the inverter itself. I found a manual for the HF24-2500SX
http://www.mpandc.com/resources/HF24-2500SX.pdf states:
HOW TO USE THE CHARGER:
Each standby unit is supplied with a standard 3 w i r e AC line. cord protruding from the center of the back, this is used to plug in the charger. In the simplest scenario this is plugged into a 120 volt AC socket at which time the Heart will recharge the battery bank. The batterv charger may be turned off and on with the power switch. This switch must be in the on position for the battery charger to operate.