Forced Air Furnace

[Dave Fritz]

We have a forced air furnace and had a humidifier installed yesterday. The technician mentioned to leave our fan running all the time. It makes sense when I think about it as the furnace motor is important to other functions, not just heat. There's a hot air exchange, an air filter and now a humidifier. The fan is important to all those not just heat I guess. What are your thoughts regarding a furnace fan running 24/7.

[Rich Engelhardt]

From what I gather, this 24/7/365 thing with the fan started a few years ago.
We had our furnace replaced in November 2020 and they told us the same thing.
Switch the fan to on, not auto, and leave it there all the time.

We had to have the furnace replaced in one of our rentals a year prior to the one we had replaced and they never mentioned anything about the fan.

Same outfit did the work & used the same brand of furnace.
I think it's a Trane.

I'd ask my wife, but, she just let the dogs out of the bedroom & judging by the tone in her voice, I'm not going near her until - maybe noon - of June - 2023 - if then.... :O

[Ron Citerone]

I only put the fan on constant at night in the summer when the AC is on to keep the cool air circulating to the second floor. My house has floor registers as it was built without AC back in the day.
Not sure I would want my humidifier running without the heat on. Others may know more about this. With my fan on auto, my April-aire humidifier works ok in Southeast PA winter weather.

[Dave Fritz]

I only put the fan on constant at night in the summer when the AC is on to keep the cool air circulating to the second floor. My house has floor registers as it was built without AC back in the day.
Not sure I would want my humidifier running without the heat on. Others may know more about this. With my fan on auto, my April-aire humidifier works ok in Southeast PA winter weather.

I was told the humidifier will only work when the sensor in the unit calls for it? I don't think it has a blower of it's own, it uses the furnace fan to circulate the air. He set it at 40% but I'm going down to 35%. Its cold out now and we'll get lots of condensation. Be nice if one was made that self adjusted to outside conditions.

We have a stand alone propane stove (Hearthstone Bristol) in the living room and that's where the thermostat is so the furnace rarely comes on during the day.

[Jim Becker]

We have a forced air furnace and had a humidifier installed yesterday. The technician mentioned to leave our fan running all the time. It makes sense when I think about it as the furnace motor is important to other functions, not just heat. There's a hot air exchange, an air filter and now a humidifier. The fan is important to all those not just heat I guess. What are your thoughts regarding a furnace fan running 24/7.
Running the fan full time is normal for a multi-speed fan system as it keeps air circulating and helps with more even temperatures throughout the conditioned space. There is no physical issue with this practice as the equipment is designed to support the practice. It's driving me nuts that the system we have here in our new place doesn't permit running full time nor is it multi-speed as I'm used to the benefits for the last two decades at our previous home.

[Frank Pratt]

My Honeywell thermostat has a "Circulate" function for the fan. It will run the fan about 30% of the time even if there's no call for heating, cooling, or humidification. We used to run it 24/7, but went through motors about every 10 years. When the motor goes, it's always been bearings, so runtime is what is killing the motors.

The circulate feature keeps the temps about as uniform as full time running, the motor will last longer, and there is substantially less energy consumption.

[Ron Citerone]

I was told the humidifier will only work when the sensor in the unit calls for it? I don't think it has a blower of it's own, it uses the furnace fan to circulate the air. He set it at 40% but I'm going down to 35%. Its cold out now and we'll get lots of condensation. Be nice if one was made that self adjusted to outside conditions.

We have a stand alone propane stove (Hearthstone Bristol) in the living room and that's where the thermostat is so the furnace rarely comes on during the day.
My system is about 16 years old. The humidifier only runs water when the sensor calls for it AND the fan on. My humidistat does not have self adjust for outside conditions.

[Bruce Wrenn]

Jim, does your thermostat not support the run function on the furnace? If so, change out the thermostat to one that does. Frank, Older motors had sleeve bearings, which required servicing(oiling.) The original in our Carrier only lasted 38 years, on continous run. The newer motors have ball bearings. For oiling sleeve bearings on a fan motor, you need a "Zoom Spout" oil bottle. It has a pull out spout that allows reaching the fan side bearing without pulling fan off shaft. Most fans are mounted on a slide out rails system, so it's easy to service them. Disconnect the power, open blower door, and slide fan out.You can reach front bearing by passing spout down thru blower wheel

[Paul F Franklin]

We run the fan on low 24/7 during the winter and on med/low during the summer. It evens out the temp throughout the house, and keeps the filter and electronic filter busy cleaning the air.

[Lee Schierer]

Our system has central heat and A/C. During the day the thermostat is set to run the fan on low to balance the temperature within the house from the sun load.

[Frank Pratt]

Jim, does your thermostat not support the run function on the furnace? If so, change out the thermostat to one that does. Frank, Older motors had sleeve bearings, which required servicing(oiling.) The original in our Carrier only lasted 38 years, on continous run. The newer motors have ball bearings. For oiling sleeve bearings on a fan motor, you need a "Zoom Spout" oil bottle. It has a pull out spout that allows reaching the fan side bearing without pulling fan off shaft. Most fans are mounted on a slide out rails system, so it's easy to service them. Disconnect the power, open blower door, and slide fan out.You can reach front bearing by passing spout down thru blower wheel

The OEM motor that came with the Lennox furnace had sleeve bearings & oil ports, so no problem. It lasted for something over 15 years. The 3 motors I'm put on since have also had sleeve bearings, but no oil ports. They've lasted 5+ years for the first 2, the 3rd is still going. I can special order a ball bearing motor, but it's about 3X the price, but also is special order. When you need a motor, you need it now.

I've installed control systems on around 100 furnaces in institutional installations in the last few years & I don't believe any of them had ball bearings. They are all direct drive blowers with "permanently lubricated" sleeve bearings.

[Jerome Stanek]

My old Lennox had bushings that went bad after 10 years in the middle of winter on a weekend. I had an old oak pallet that I used a hole saw the make a replacement to get me by. I soaked them in oil and installed them hoping to get me by until I could get new ones. I bought some and figured I would replace the wood ones when they go bad. That was 30 years ago and the bushings are still in my cabinet and the blower is still going strong as a air mover in my shop.

[Aaron Rosenthal]

Jim, I replaced my thermostat a few years ago with an Ecobee programmable/IP enabled unit, and I can control the fan cycles, heat levels and times from either the unit or via my phone/ipad or computer.
One of the best decisions I've ever made for my "i'm freezing" family.
My Trane furnace is a 2001 model, not even energy efficient that it's made any more.
Next step will be a heat pump.

[Jim Becker]

Our current thermostat provides app based control here in the new property. Unfortunately, the HVAC system cannot use many of the features because of how it was designed. Heating is heat pump with oil to cover as temps drop. It's not an efficient heat pump like a mini split and the system design only supports one fan speed...on or off. :( The conundrum here is that the HVAC system is only 5 years old so replacing it "soon" isn't a very practical project financially.

[Brian Elfert]

Running your furnace fan can often result in the house feeling more comfortable. My parents always run their fan. Their 1994 furnace just ran full speed all the time. Their newer furnace has an ECM motor and runs at a lower speed when the system is not heating or cooling. An ECM motor is supposed to use less energy. My furnace has the old style single speed motor so it can feel drafty if I run the fan all the time in the winter.

My house can feel cool when the temperatures are in the 30s because the furnace is not running much. I think running the fan helps then, but it also feels somewhat drafty. I don't like running the fan all the time due to the electricity cost.

[Alan Lightstone]

We have a new high-end TRANE unit on order (ah, supply chain issues...). The salesman told us it is variable speed, and is constantly running. Our present TRANE units are variable speed, but are not constantly running. So their design has changed over the past 12 years. I closely monitor our energy usage, so I am very interested in seeing if this saves or costs energy. Time will tell.

[Lee Schierer]

We have a new high-end TRANE unit on order (ah, supply chain issues...). The salesman told us it is variable speed, and is constantly running. Our present TRANE units are variable speed, but are not constantly running. So their design has changed over the past 12 years. I closely monitor our energy usage, so I am very interested in seeing if this saves or costs energy. Time will tell.

Our thermostat controls the fan running on low speed, even on our old Carrier heat pump. Check your thermostat settings to see if it is an option, or possibly a new thermostat,less costly than a new unit.

[Jim Becker]

Alan, my thought is the same as Lee...I believe if you set the fan to "on" in the thermostat, it will run full time, but only at the speed necessary. But it's a moot point long term given you have the new unit on order. You could play with it just for grins. :)

[Ronald Blue]

My old Lennox had bushings that went bad after 10 years in the middle of winter on a weekend. I had an old oak pallet that I used a hole saw the make a replacement to get me by. I soaked them in oil and installed them hoping to get me by until I could get new ones. I bought some and figured I would replace the wood ones when they go bad. That was 30 years ago and the bushings are still in my cabinet and the blower is still going strong as a air mover in my shop.

Actually oak bearing blocks were used extensively in older style combines with straw walkers years ago and lasted very well. Pretty much out of sight out of mind. I think but not positive we just gave them a shot of oil and they were good to go for a long time.

[Alan Lightstone]

Alan, my thought is the same as Lee...I believe if you set the fan to "on" in the thermostat, it will run full time, but only at the speed necessary. But it's a moot point long term given you have the new unit on order. You could play with it just for grins. :)

I do know that my Nest thermostat allows a fan on setting. I had no idea this would be variable speed, though. I always figured this would cost energy. At present it turns on and off all the time.

As it turns out, we won’t be able to use those Nest thermostats with the new Trane unit. Pretty sleezy if you ask me, requiring you to use their proprietary thermostats. Hopefully the web interface will be decent.

[Jerome Stanek]

Actually oak bearing blocks were used extensively in older style combines with straw walkers years ago and lasted very well. Pretty much out of sight out of mind. I think but not positive we just gave them a shot of oil and they were good to go for a long time.

Our farmers exchange had oak bushings in their grain elevator that was installed in 1919 and still running up to 2019 when the building was condemned.

[Tom Bender]

The hours per year on a grain elevator are a little less than 24/365