Do furnaces have cool down cycles before shutting off?

Sarahanna

I have been having a lot of issue with the furnace lately, however I rent and my landlord isn't the greatest so I am trying to figure out if this is normal or not. My furnace goes on fine but when it reaches the desired temperature instead of just shutting off it blows cold air for roughly 2 minutes which they just makes the house cold again and then it kicks back on and so on. Is it normal for that to happen because I have never dealt with that before or maybe just never noticed but this is really cold air so it's noticeable. I did have a problem over the summer where the furnace just kicked on and was blowing cold air non stop even though the thermostat was all the way down to 50 and the landlord came and did something with the blower switch I believe he said but I have no idea. I tried to look for a serial number or anything on the furnace but all the one panel says "Nordyne by Nortek" but I couldn't find anything else but it's really old I can tell that.  So is that normal?

Steamhead

Yes they do

in the old days this was handled by a thermostatic "fan and limit control", now I believe many furnasties use timers to run the fan for a bit after the burner shuts off. You'd want to check with someone who is familiar with your unit- it's been a while for me.

Jean-David Beyer

instead of just shutting off it blows cold air for roughly 2 minutes

My Quaker Meeting's building is two zones of forced hot air heating. Two furnaces (one for each zone) provide the heat. The blowers forcing the hot air around turn on when the temperature of the plenum gets warm (not to full temperature) and they run until the air in the plenum cools down quite a bit. We are talking about less than 60 seconds here. So when the thermostat is satisfied, the fire goes out, but the blower continues to run until the air cools down. It does not blow cold air because the air returning to the furnace is not colder than the air in the controlled heated space. These (gas-fired) furnaces are between 10 and 15 year old Rheem units; they are not condensing models.