Jump in house temperature

[garrett1812]

I have a 2 story house (2350sq ft) plus unfinished basement. There is one gas furnace for the house, and it is not a zoned system. The basement has just two registers and stays an okay temperature, whatever it may be (65ish). Usually when the main level (where thermostat is installed) is at 72, the second story will be ~72-75. Now all of a sudden the second story is ~78-80. Happened for the last 2.5 days. I haven't made any changes to the registers, samplers, etc. no windows or exterior doors open, no change in interior doors (normally all open except basement), weather has been same for about a week. Any idea on other things to look for?

Thanks!

 

[gungatim]

I'd check that all the first floor vents are open and getting good flow. could be something fell and stuck in one. also do you close off the upstairs registers? we do for that very reason.

also check your furnace filter. if it's clogged and not getting enough air flow it will maybe run longer to get up to temp allowing more time for the heat to rise maybe?? just a guess there but that's what I'd do...

 

[bzinsky]

Yeah I'd check all your vents, as you probably understand, somewhere on the first floor heat is either not coming in or it's escaping somewhere.

Home depot rents a thermal imaging camera that works well if it comes down to it

 

[garrett1812]

Good thought on the filter, I will check that.
I did check all the vents, none have been accidentally closed or covered.

 

[gungatim]

I meant to check the vents are blowing. could be something fell in, mouse nest, or the damper adjustments in the basement could have vibrated closed or gotten accidently knocked. our vents are all floor mounted, and returns are in the wall but often get covered by something by mistake lowering the airflow. the one in the kitchen is near the trash, so you know how stuff can make it in there...good luck.

 

[tomroblee]

You didn't mention the age of the house (or heating system) or how long you have lived there.

Are the "normal" conditions you describe based on several years experience? )(If you just recently moved into the house you may not have experienced the recent weather pattern before.)

Most modern duct design calls for dampers to be installed in the main ducts that lead to the various parts of the house. Their purpose is to allow you to balance the air flow and/or change it by season. If you have such dampers, one or more may have been inadvertently moved.

If you have a leaky duct somewhere I could do some strange things. Some of the first floor air flow may have been directed to the basement---where you might not notice it.

The first floor thermostat may be reacting differently is anything has changed the air flow around it. This could be caused by moving a piece or furniture or just a "dust bunny" collecting in the thermostat.

You said that there are no doors or windows open. Have you checked for a stuck open damper on a fireplace, bathroom exhaust fan, range hood, clothes dryer, or ??

 

[Falcon67]

FWIW, in my house owning experience 2400 sq/ft is marginal for a single HVAC unit. Heat travels up easy - ask me how I know, working in a 3 story building on ancient a 2 pipe system with chilly people in the lower floors. We have windows open on the 3rd floor with fans running even when it's below freezing outside. (if the system is working LOL).

Anyway...make sure the change in weather isn't just forcing your system to pump more heat to maintain the lower floor temp, which will drive the 2nd story temp up by the nature of the effort. Been there, owned that, fortunately in a mild climate.

If you don't have a "smart" thermostat, consider updating to a wifi gizmo that works with your system and maintains run time data. You can tell right away how hard the system is working. Filtrete has some like that.

 

[garrett1812]

House is about 2 years old. We have lived there for 1.5 years. "Normal" conditions are this past winter, and this winter thus far.

I actually do have a smart thermostat (ecobee3), but will left out the details because I don't use most of the smart features. But I do have a lot of data to look at, including sensors on both levels.

 

[gungatim]

wait--you have sensors in both locations? and it's not zoned. that may be something to look at then. not sure how that works but assume there is some algorithm that compares the two to call for heat? maybe a programming change in the t-stat or a bad upper sensor?

 

[garrett1812]

Not zoned. I have it set to heat the house to 72 degrees, based on the main living area on the floor level from 7am to 10pm, then to heat the house to 72 degrees based on the bedroom on the second story from 10pm to 7am. This strategy has made the house much more comfortable, until the last few days.

 

[garrett1812]

Mystery solved. Turns out it was the "smart" thermostat (despite being used like a relatively dumb thermostat). They reviewed the data and the algorithm is going haywire.