I’m in a pretty cold state. It’s been below zero F quite often this winter. My furnace has not been keeping up and my house has gotten pretty cold. I got some space heaters to supplement.
Furnace is about eight years old.
But I started to think that I’ve never had this problem in past winters. Maybe furnace needs a tune up? I always keep a clean filter and air volume from vents was fine. All gas jet thingies were fired up and looked fine.
So I started thinking that this past summer I switched my system to always ON because I thought maybe constantly circulating the AC on the house would keep the temp low with less energy. Plus I didn’t like the system turning on and off when I was trying to fall asleep.
This is a 100 year old house with no insulation. I retrofit the central AC and heat in 8 years ago.
So I’m trying to figure out why the heat won’t keep up and I decide to switch the system to Auto. We had a really cold night and it kept up just fine. The house is hot now!
Is this normal? If not is it indicative of a problem?
Best Answer
Running the fan reduces stratification, meeting that it makes the temperatures in the house even. The thermostat being centrally located in a house is often satisfied before the remainder of the house is able to warm up especially in an old house where the heating registers usually are centrally located what's return air located at outside walls. In a house with no insulation the exterior walls lose heat much faster than the heat can be replaced from the ambient air within the house. Basically it's an indication that you have a poor duct system which is not uncommon in an old house.
If you let me know the state, square footage not including the basement if it's below ground, the furnace model number or the size in btu I can tell you a little more about your system.
Edit
Although the above statements are very accurate I did interpret your question in reverse. I read it as, you were having a problem maintaining the temperature with the fan set to auto.
Having your issue with the fan set on would normally be a real head-scratcher. But in this case I would say you need to have a look at your Ecobee. It's a fantastic thermostat, I have one too and there are a lot of features available to tweak your system. If you have multiple sensors and and they are satisfied before the main thermostat the system may shut off prematurely.
This is a screenshot of my ecobee
If the sensor upstairs reaches the temperature set point well ahead of the main thermostat I think ecobee uses some kind of average to determine when to shut it off.
To determine if this is the issue I would suggest turning off all the sensors except for the main thermostat run the fan set to on and see if anything changes.