If there are clogs anywhere in the condensate line the system will freeze.
Condensate furnace drain line freezing.
Blocked condensate lines the condensate lines in your hvac system are responsible for draining the excess moisture caused by humidity.
With the pipes blocked the condensate backed up into the furnaces where safety switches shut the units down.
A clog can prevent moisture from exiting the system allowing it to pool up within your unit.
The basement has no drain so the the persons that install the furnace ran pvc pipe through finished walls under the concrete floor inside the house and under the patio outside.
In reality a major repair may not be necessary as thawing the frozen drain lines should fix the issue.
When that happens most hvac systems are designed to shut off completely leaving homeowners scrambling for a solution.
They did not bury the pvc very deep about 3 inches thus when temperaturs go lower that 20 degrees for a couple of days the condensate inside the pipe freezes and back up.
Shortening the drain pipe to give water less space in which to freeze can also be effective.
The moisture is drained through pipes leading to the floor drain.
The best way to stop condensate drain line freeze is to use weather proof sleeves placed around the drain.
Shorten the pipe outside so that there s less area exposed widen the pipe at the end if the ice starts at the end from the drip expanding it to 4 might work insulate or heat the pipe using heat tape or something like that which i don t know anything about something else.
During periods of snow verify that snow hasn t risen to the level of the drain line where it can block it and cause further freezing.