My friend is taking care of my 25 year old home in British Columbia (Canada) and all breakers were switched off when I went away, except for the Main at the bottom and the garage one for him to be able to activate the garage door to access the garden tools. Now he needs to turn some heaters on in the house to keep the temperature inside above 10C as the weather is cooling down, but most breakers seem to be set up by set of four, with a top-bottom tandem (linked by a metal plate) and a middle tandem (linked by a small bar).
The pic shows the panel configuration after he switched some breakers ON, but I wonder if there are any rules when selectively switching some of these linked breakers ON and OFF? Anything to be careful about? I am concerned with fire hazard as there is nobody in there to detect a problem (short circuit, etc.).