Gas furnace slow to heat?

3 hours for your furnace to elevate your household temperature 8 degrees? What was your experrience prior to intallation of the blower?

When was the last time you replaced the filter? If the filter is real dirty the furnace may hit the high temperature limit and shutoff.

Are you certain that the motor was installed correctly? Don’t laugh; it can happen.

A fan motor that is installed with the wrong rotation will turn on and run a centrifugal fan just fine, but if the fan is turning backwards then the blades will be very inefficient.

But you tell us:
1. Does the furnace run for all of the three hours? Does the fan?
2. What is the air flow like from the ducts, especially compared to the old system?
3. Were any duct dampers closed during the replacement process – and then not re-opened afterward?

First check the air filters. Especially if they haven’t been replaced this season. Those things can dirty up quicker than you might think.

Barring that – call whoever installed the motor. You might have to do some haggling, but if they installed it incorrectly or gave you the wrong motor for the furnace then they should ultimately fix the issue at little to no charge.

Lastly, more powerful isn’t necessarily better. A motor can be more powerful than the furnace is built for. This happened to me a few winters back. The motor died on my furnace, I called a local furnace/air repair business that’s known for having a solid reputation around here. They installed a motor that was too strong for what the furnace was built for. It broke the bracket that holds the motor in place, so the motor was just kinda hanging there inside the furnace. It was running but it wasn’t really creating the air flow that it should.

Did they reuse the existing squirrel cage? It doesn’t sound like the fan is properly installed/positioned in the fan shroud/housing. Does the air seem to blow out of the vents like the old motor? Maybe you should have another HVAC tech check it out. Maybe they wired the motor wrong and it’s turning in the wrong direction. (CW vs. CCW)

Thank you so much for all of your replies. After I a phone call, the serviceman came out to take a look (thankfully free of charge) and said he made a couple of adjustments and told us to keep an ear and eye on it. He says could be a case of the motor being too powerful for the furnace. He will replace the new motor with the type that was originally in place if the problem continues, which it has done. Why he used something other than this is beyond me. It seems as if there must be specs on what motor goes with what furnace. Anyhoo, I will let you know as soon as he replaces it whether the NEWEST motor does the job it is supposed to.

UPDATE: The furnace serviceman came back out and replaced the noisy, too powerful fan with the (correct) quieter one that heats our home much more quickly. My ears are no longer ringing and my toes are finally warm. Thanks again for your help!

Glad to hear you got it fixed!