Is this furnace oversized?

Question

We got a new furnace installed. The upstair unit turns on and off about 15-20 minutes, but the downstair unit turns on and off every 10 minute, which creates noise sound. And the return vent creates more noise.

1. Is it normal for the furnace to turn on and off every 10 minutes to maintain the desire teperature? Is it a way oversized?

2. Is our duct too small for the new furnace? If we lower the speed of the new furnace, will it be okay?

Any advice would be appreciated.

Answer 1

First, I would try installing a new thermostat. My furnace did about the same thing: turn on, run for about 10 min., shut off, come on about 10 min. later. I swapped the thermostat for a better quality programmable one and it worked fine.

I don't hthink it is oversized just from these symptoms and I wouldn't mess with the blower speed, especially if you have A/C. This will mess with the airflow and could potentially burn the A/C compressor.

Try the thermostat and go from there. If this doesn't work, call your contractor and see what he/she recommends. If the contractor is like mine was, you won't get any results, so maybe call a different one and get another opinion. Good luck.

Answer 2

I'm sorry I don't know if it's oversized.

But what I've heard is that there are newer systems that are designed to maintain your indoor temp at a very small margin. so rather than letting the house cool by 4-5 degrees and then running longer to get it to the thermostat temp.
They keep your home within just 1-2 degrees range of the setting on the thermostat.

I think that may be why it seems different.
i wouldn't hesitate to call the co that installed it for more info.