If you only had one system and one thermostat cool air falls hot air rises.
Furnace not heating second floor.
Units older than 10 years should be upgraded.
In some cases it s because the system is outdated.
The most common complaint regarding imbalanced temps and hvac units is that it cools the first floor but not the second floor.
Leaking air ducts if the ducts connected to your second floor are leaking cold air then of course your upstairs will not be cold.
This is an expensive option but it provides the most heat.
Learn how to test your air ducts for leaks.
Having a 2nd system on a 2nd floor delivers better controllable comfort.
A dirty furnace filter can limit the airflow through your furnace and cause it to overheat which will shut it off automatically.
Chances are your prv water feeder is not working.
Unfortunately the average air duct system lose around 20 30 of its conditioned air to cracks and gaps i the ductwork.
You lost pressure on the system so you had enough pressure for the first floor but not the second floor.
See if you can follow the pipe from the boiler through the whole zone and.
The other possibility is that it might be frozen at some point near an outside wall.
As you can see many of these issues are not easy to identify as a homeowner.
When your furnace just isn t powerful enough to heat your second floor install a second furnace dedicated to your upstairs area.
Thermostat is only reading the temperature of the floor that is being heated cooled.
There would be one for each zone.
Your furnace or air conditioning system isn t the right size for your home.
Dirty furnace filters are one of the most common causes of furnace failure.
Get the pressure to 15 psi and bleed the second floor and itshould heat.
In other words the lower level is always too chilly and 2nd floor is always too hot.
A well trained hvac professional can test and assess your system to help you identify the real cause of your heating and cooling issues and determine the best solution for your home and your budget.