How do I prevent my Mac from switching Wifi connections when at home?
Looks like the computer is set to prefer or prioritise the xfiniti Wifi hotspot over you home wifi, you can set your home Wifi to be of priority to any other Wifi connection and this is how to do that, 

System Preferences/Network/ then select Wifi and click on Advanced, you'll see all preferred networks there. 

Click and drag your home Wifi to the top.