A frozen condensate line is a hidden cause of furnace problems in cold Alberta homes. High-efficiency furnaces produce water that drains through a small tube or condensate pump. If that line clogs or freezes where it passes through a cold space, a safety switch shuts the furnace down. Sherwood Mechanical explains the warning signs to look for, like water around the furnace or a full condensate pump, and when this issue needs a professional. Learn more in our full furnace not working guide.