Running Blower 24/7

Reply

  #1  
Old 01-10-09, 02:05 PM
Member
Thread Starter
Join Date: Sep 2008
Location: USA
Posts: 134
Running Blower 24/7

Howdy.

I like the idea of running my air handler (furnace) at low speeds 24/7 during the summer season for several reasons:

- Reduced air stagnation around the house
- Continous air filtration
- Less chances of building mold in the duct system/a-coil
- Possible less electricity consuption (no startup spikes)
- Possible longer equipment life (less blower on/off)

Are there any drawbacks to doing this? I read at another site saying it's a bad idea, but it did not make any sense to me.
 

Last edited by joe1234; 01-10-09 at 02:56 PM.
Sponsored Links
  #2  
Old 01-10-09, 02:55 PM
Member
Join Date: Jul 2008
Location: johnson county, ks
Posts: 338
It is a good idea during heating times when people are home. Not so good other times.

1) Your electric bill will go up. How noticeable depends on your rates.
2) You will go through filters much much quicker.
3) Shorter equipment life. The only thing that extends the life of a product is less usage.
4) During AC season, it will raise the humidity just a bit due to evaporationg the condensed water off of a coil that just shut off.

The only time leaving a fan on really is a reasonable decision is if you have a variable speed ECM blower motor. Do you know what type of motor your blower has?
 
  #3  
Old 01-10-09, 03:03 PM
Member
Thread Starter
Join Date: Sep 2008
Location: USA
Posts: 134
Originally Posted by badtlc View Post
It is a good idea during heating times when people are home. Not so good other times.

1) Your electric bill will go up. How noticeable depends on your rates.
2) You will go through filters much much quicker.
3) Shorter equipment life. The only thing that extends the life of a product is less usage.
4) During AC season, it will raise the humidity just a bit due to evaporationg the condensed water off of a coil that just shut off.

The only time leaving a fan on really is a reasonable decision is if you have a variable speed ECM blower motor. Do you know what type of motor your blower has?
I am in the process of selecting a system and yes, I am loooking that the variable speed blower motors like the Goodman GCV9.

With respect to the items you mention, here is what I am confused about.

1) Variable speed motor furnaces make the opposite claim, so which is it?

2) My lungs filter the air or a filter? I will pick filters any time over my lungs.

3) Is this true? For motors, constant on/off is not good and shortens life in general.

4) Correct, but this is exactly what is good about it that molds wont grow.
 
  #4  
Old 01-10-09, 04:03 PM
Member
Join Date: Jul 2008
Location: johnson county, ks
Posts: 338
Originally Posted by joe1234 View Post
I am in the process of selecting a system and yes, I am loooking that the variable speed blower motors like the Goodman GCV9.

With respect to the items you mention, here is what I am confused about.

1) Variable speed motor furnaces make the opposite claim, so which is it?

2) My lungs filter the air or a filter? I will pick filters any time over my lungs.

3) Is this true? For motors, constant on/off is not good and shortens life in general.

4) Correct, but this is exactly what is good about it that molds wont grow.
1) Variable speed motors save money during run times vs. standard motors. A variable speed motor running all the time will cost more to operate than a variable speed motor only running during heat/cool cycles.

2) Unless your system is severely oversized, it shouldn't really filter much better running the fan all the time. You are getting a bit melodramatic by insinuating you are sacrificing your lungs. As a side, if you go all out and get a high filtration filter to protect your precious lungs to the max, your electric bill will go up noticeably.

3) Constant on and off would mean short cycling. Again, not a problem at all if your system is properly sized and not over sized.

4) Mold will not be a problem as long as a system is properly installed. The drain pan and drain piping should eliminate that problem itself. Raising the humidity in the house can lead to uncomfort and wanting to lower the set point during AC season.

Everything all depends on your installation. If you are getting an ECM blower furnace, make sure your installer properly sizes your equipment. If they install a blower that is too big for your ducts, the installation will be very noisy AND your electric bill will shoot up. ECM motors try and maintain CFM despit high static pressures from undersized duct work.

Like I said earlier, the only time running a blower constantly really makes sense is when it is heating season and people are home. I have experimented with mine (Amana AMV8) and can verify everything I have said above.
 
  #5  
Old 01-10-09, 05:15 PM
airman.1994's Avatar
Member
Join Date: Dec 2005
Location: VA
Posts: 5,727
Likes Received: 3
Setting the record straight!
Running the fan in the on position in the winter is recommend to circulate the air so home has more even temps. You will have filtered air all the time. Starting a motor is the worst thing you can do to it (just like a car). Energy cost will be just some change a day, but the benefits out way the cost. I will agree that running the fan in the on position in cooling time will increase RH by 7 to 10%. It was stated that mold will not be a problem if equipment is properly installed. I see mold in about 80% of the equipment I look at. AHU have the perfect place to grow mold.
 
  #6  
Old 01-10-09, 05:30 PM
Jarredsdad's Avatar
Member
Join Date: Oct 2002
Location: Troy, VA
Posts: 1,532
Originally Posted by badtlc View Post
Everything all depends on your installation. If you are getting an ECM blower furnace, make sure your installer properly sizes your equipment. If they install a blower that is too big for your ducts, the installation will be very noisy AND your electric bill will shoot up. ECM motors try and maintain CFM despit high static pressures from undersized duct work.
I remember the Doctor who had a 7 ton Geothermal unit with ECM blower in his zoned house.

He wondered why the unit seemed like it was bouncing around his attic. The system was set up for 2000 CFM. And, the zoning would start the unit if only one zone called. The motor will go as fast as it can trying to deliver 2000 CFM.

It will also go slower if it needs too.

If you leave your ECM fan in on 24/7 it will run 50% when not cooling or heating.

The temp in your house will be more even throughout. Your system may run less often because of the constant air movement.

Been in this industry (crap) almost 25 years. Guess what ECM AH running 24/7.

The guy I work for had 25 years when I started. 3 speed AH running 24/7.

Used pleated filters and change 'em every 30 days.

Live long and prosper.
 
  #7  
Old 01-10-09, 05:53 PM
Member
Join Date: Jul 2008
Location: johnson county, ks
Posts: 338
Originally Posted by airman.1994 View Post
Setting the record straight!
Running the fan in the on position in the winter is recommend to circulate the air so home has more even temps.
The winter definitely benefits the most.
 
  #8  
Old 01-10-09, 05:57 PM
Member
Join Date: Jul 2008
Location: johnson county, ks
Posts: 338
Originally Posted by Jarredsdad View Post

If you leave your ECM fan in on 24/7 it will run 50% when not cooling or heating.
Have you ever took a reading when the fan is in 50% to see what kind of power draw it was consuming? I have seen some as low as 70w and some as high as 200w (only ECMs). What do you normally see?
 
  #9  
Old 01-10-09, 07:29 PM
Jarredsdad's Avatar
Member
Join Date: Oct 2002
Location: Troy, VA
Posts: 1,532
No I haven't. Don't really care, to be honest. Fan runs 24/7. Heat or A/C speeds up fan, humidifier runs as needed. Filter cost and changes are starting to tick me off.
 
  #10  
Old 01-10-09, 07:49 PM
Member
Join Date: Jul 2008
Location: johnson county, ks
Posts: 338
Originally Posted by Jarredsdad View Post
No I haven't. Don't really care, to be honest. Fan runs 24/7. Heat or A/C speeds up fan, humidifier runs as needed. Filter cost and changes are starting to tick me off.
I was just curious because some of my friends were wanting to run their fans 24/7 until they realized that they'd end up paying about $200/year to do that.
 
  #11  
Old 01-11-09, 10:36 AM
Member
Thread Starter
Join Date: Sep 2008
Location: USA
Posts: 134
Originally Posted by Jarredsdad View Post

Been in this industry (crap) almost 25 years. Guess what ECM AH running 24/7.

The guy I work for had 25 years when I started. 3 speed AH running 24/7.

Used pleated filters and change 'em every 30 days.

Live long and prosper.
I have the AprilAire filter system which has been Great for me. I change mine every 6 months (or sooner) and it is amazing how dirty it gets.

A new AprilAire 4200/4400 just came out with Merv 13 filtration which is what I am upgrading to with the new HVAC system when I get it.

On a side note. The point has been made that having a ECM motor with undersized duct work will make the ECM motor fight and thus run faster and harder than necessary to maintain proper air flow (CFM).

So my question is, is there a problem with having larger than necessary duct work when considering an Air handler (Furnace) with a ECM motor (variable speed motor)?
 
  #12  
Old 01-11-09, 11:57 AM
Member
Join Date: Jul 2008
Location: johnson county, ks
Posts: 338
Originally Posted by joe1234 View Post
On a side note. The point has been made that having a ECM motor with undersized duct work will make the ECM motor fight and thus run faster and harder than necessary to maintain proper air flow (CFM).

So my question is, is there a problem with having larger than necessary duct work when considering an Air handler (Furnace) with a ECM motor (variable speed motor)?
Yes, if some blowers don't detect enough static pressure, they will shutdown.
 
  #13  
Old 01-11-09, 06:29 PM
Member
Thread Starter
Join Date: Sep 2008
Location: USA
Posts: 134
Originally Posted by badtlc View Post
Yes, if some blowers don't detect enough static pressure, they will shutdown.
On the intake, output or both? True of most air handlers with varaible blowers?
 
  #14  
Old 01-12-09, 05:59 AM
Member
Join Date: Jul 2008
Location: johnson county, ks
Posts: 338
Originally Posted by joe1234 View Post
On the intake, output or both? True of most air handlers with varaible blowers?
The blower can only measure the static it sees. I guess that would be total system static pressure. I think in order to have that problem you'd have to be running 2 ton unit on ducts sized for 5 ton or some other severely undersized matchup.
 
  #15  
Old 01-13-09, 11:07 AM
Member
Thread Starter
Join Date: Sep 2008
Location: USA
Posts: 134
Any way to do a poll here?

So it looks like the majority of the responses say to leave it running 24/7?

The issue of electricy consuption has been made, so this is comfusing as I thought leaving a motor running slowly was better and consumed less electricity than starting and stopping.

According to the Goodman GCV9 93% efficiency variable speed furnace ( http://www.goodmanmfg.com/Portals/0/pdf/CB-GCV9.pdf ) it claims that running the blower at low speed is equivalent to having a 75 watt light bulb on. Any knows how true this is?
 
  #16  
Old 01-13-09, 12:19 PM
Member
Join Date: Jul 2008
Location: johnson county, ks
Posts: 338
Originally Posted by joe1234 View Post
Any way to do a poll here?

So it looks like the majority of the responses say to leave it running 24/7?

The issue of electricy consuption has been made, so this is comfusing as I thought leaving a motor running slowly was better and consumed less electricity than starting and stopping.

According to the Goodman GCV9 93% efficiency variable speed furnace ( http://www.goodmanmfg.com/Portals/0/pdf/CB-GCV9.pdf ) it claims that running the blower at low speed is equivalent to having a 75 watt light bulb on. Any knows how true this is?
I can let you know more tonight about my system. I have an Amana AMV809 furnace set for a 3-ton Amana ASZ16 heat pump (about 1200CFM high cooling). I'm taking my amp probe home from work to measure the current draw in constant-on mode. If it is 75W i'll be ecstatic and probably run mine 24/7 in heating season. My rates go up in summer by 2x so I doubt I would consider it then.

As a side, starting-stopping with electric motors such as these DC ECM controlled fans with soft start functions really see no wear and tear during the process. I'm an electrical engineer by both trade and education. Running them 24/7 is harder on them than starting/stopping and only running 70% of the time or so. Whether or not the degree to which the difference makes is very debatable and probably not the limiting factor in the life of a furnace.
 
  #17  
Old 01-13-09, 02:51 PM
Member
Join Date: Jul 2008
Location: johnson county, ks
Posts: 338
Originally Posted by joe1234 View Post

According to the Goodman GCV9 93% efficiency variable speed furnace ( http://www.goodmanmfg.com/Portals/0/pdf/CB-GCV9.pdf ) it claims that running the blower at low speed is equivalent to having a 75 watt light bulb on. Any knows how true this is?
Amana's have the same variable speed blower and make the same 75-watt claim. I just got done measuring my constant-on fan power consumption and it is closer to 150-watts (144W measured), not 75-watts. This could be due to excessive static pressure in my system. I haven't the tools to measure static pressure in my system so others might actually be seeing 75-watts. At $0.10/kWh, that comes out to $131/yr to run the fan 24/7.

Now, that is also a bit misleading because the fan isn't in constant-on mode 24/7. During winter and summer, it spends probably 80% of its time in cooling or heating mode. So if you assume that the fan is in constant-on for only 14 hours a day, instead of 24/7, over a 365 day year, it is actually costing you around $76/yr to leave it on. That is pennies to some, and that is a free month of satellite TV for others. To each his/her own.
 
  #18  
Old 01-13-09, 03:47 PM
Member
Thread Starter
Join Date: Sep 2008
Location: USA
Posts: 134
Originally Posted by badtlc View Post
I can let you know more tonight about my system. I have an Amana AMV809 furnace set for a 3-ton Amana ASZ16 heat pump (about 1200CFM high cooling). I'm taking my amp probe home from work to measure the current draw in constant-on mode. If it is 75W i'll be ecstatic and probably run mine 24/7 in heating season. My rates go up in summer by 2x so I doubt I would consider it then.

As a side, starting-stopping with electric motors such as these DC ECM controlled fans with soft start functions really see no wear and tear during the process. I'm an electrical engineer by both trade and education. Running them 24/7 is harder on them than starting/stopping and only running 70% of the time or so. Whether or not the degree to which the difference makes is very debatable and probably not the limiting factor in the life of a furnace.
Nice! Thanks for conducting the testing and for answering the question about stopping / running verses always on. I did not know that about these motors.
 
  #19  
Old 01-13-09, 06:13 PM
Jarredsdad's Avatar
Member
Join Date: Oct 2002
Location: Troy, VA
Posts: 1,532
This is the last I will say.

ither run blower 24/7 or not. It's your bill.
 
  #20  
Old 01-13-09, 08:58 PM
Member
Thread Starter
Join Date: Sep 2008
Location: USA
Posts: 134
Originally Posted by Jarredsdad View Post
This is the last I will say.

Either run blower 24/7 or not. It's your bill.
I rather go with an informed decision.

Case in point: I setup a mega home PVR (Personal Video Recorder) at home with 10 1.0TB disks for storing movies.

It cost me less to keep the thing up and running 24/7 than to have it sleep and resume (power up) for each recording.

If running the blower 24/7 is close to, or similar to not running it 24/7 as far as enegery consuption is concern, I rather keep it running 24/7.

Many hospitals and large building run their setup 24/7 and at low speeds when no demand is needed.
 
  #21  
Old 01-14-09, 02:08 PM
Jarredsdad's Avatar
Member
Join Date: Oct 2002
Location: Troy, VA
Posts: 1,532
True most large commercial buildings run airflow 24/7. Many use VFD's (variable frequency drives) to regulate airflow when heating/cooling/standby.

What we are trying to say is that there are 2 schools of thought in residential.

badtlc doesn't like to run 24/7 and has his reasons.
I do run 24/7 at have mine. I do miss my filter monitor being silent for 3 months until 30 days of fan run time accumulated.

You have your own reasons for asking about it which are all valid and I agree with.

Many new stats have auto/on/circ for fan mode. Circ turns on the fan about 20 minutes each hour independent of heating or cooling.

Boils down to personal preference. Try 24/7 and see if you notice a change. As I said It is your choice.
 

Last edited by Jarredsdad; 01-14-09 at 02:11 PM. Reason: Can't freakin spell
  #22  
Old 01-15-09, 06:09 AM
Member
Join Date: Jul 2008
Location: johnson county, ks
Posts: 338
Originally Posted by Jarredsdad View Post

badtlc doesn't like to run 24/7 and has his reasons.
I do run 24/7 at have mine. I do miss my filter monitor being silent for 3 months until 30 days of fan run time accumulated.
Not quite, I like running my fan in heating season. I don't like running it in cooling season.
 
  #23  
Old 01-15-09, 10:36 AM
Member
Join Date: Jun 2004
Location: us
Posts: 385
I'll give you another opinion since I lie in between. I use a programmable thermostat that allows you to control fan mode during each period. In addition, it has a circulate setting that runs the fan 33% of the time regardless of the heat/cooling demand.

During the winter, I run the fan continously during the "wake" period, 5:30-8:00. When I'm "away" it drops to auto. In the evening it is on circulate. During sleep, it is on auto.

During the summer, it is on auto, except during sleep and its on circulate. Our bedroom gets hot.
 
  #24  
Old 01-15-09, 10:49 AM
Member
Thread Starter
Join Date: Sep 2008
Location: USA
Posts: 134
Originally Posted by chris8796 View Post
I use a programmable thermostat that allows you to control fan mode during each period. In addition, it has a circulate setting that runs the fan 33% of the time regardless of the heat/cooling demand.
That may be the best compromise - if you can get the thermostat to run the fan longer then neccessary - like you said, 33% more in general regardless of head/cooling need.

What kind of thermostat is that?

I am considering the Honeywell IAQ thermostat. Anyone knows if it has an option to run the blower similar as stated above?
 
  #25  
Old 01-15-09, 02:36 PM
Jarredsdad's Avatar
Member
Join Date: Oct 2002
Location: Troy, VA
Posts: 1,532
The IAQ and the VisionPro 8000 has Circ on it. Also fan off delays fro heat and cool.

Component
 
  #26  
Old 01-15-09, 02:53 PM
Member
Join Date: Jun 2004
Location: us
Posts: 385
I have the honeywell TH8320U1008

Its part of the visionpro 8000 family, very nice thermostat. I also got the outside temperature sensor for it, I saw the coldest reading yet today, -17F.
 
  #27  
Old 01-15-09, 03:20 PM
Jarredsdad's Avatar
Member
Join Date: Oct 2002
Location: Troy, VA
Posts: 1,532
Where are you Chris?

We are in a nose dive here. 39 at 5pm, not 1 1/2 hour later 22 and falling.
 
  #28  
Old 01-15-09, 05:07 PM
airman.1994's Avatar
Member
Join Date: Dec 2005
Location: VA
Posts: 5,727
Likes Received: 3
Originally Posted by Jarredsdad View Post
Where are you Chris?

We are in a nose dive here. 39 at 5pm, not 1 1/2 hour later 22 and falling.
You on call this weekend! Went down 64 today to Richmond I didn't see you.
 
  #29  
Old 01-15-09, 05:22 PM
airman.1994's Avatar
Member
Join Date: Dec 2005
Location: VA
Posts: 5,727
Likes Received: 3
Originally Posted by Jarredsdad View Post
Where are you Chris?

We are in a nose dive here. 39 at 5pm, not 1 1/2 hour later 22 and falling.
JD just in case you you forgot! Lynchburg Weather Forecast and Conditions Virginia (24502)
 
  #30  
Old 01-15-09, 06:39 PM
Jarredsdad's Avatar
Member
Join Date: Oct 2002
Location: Troy, VA
Posts: 1,532
I went to Winchester today. Drove through a small snow squall.

You beat us by 2 to 3 degrees in the forecast.

It's 16 out now, your link says 15 for you.

Nice here, inside.
 
  #31  
Old 01-15-09, 06:54 PM
Member
Join Date: Jun 2004
Location: us
Posts: 385
I'm in central IL, so this is not normal. It currently reads -12. They already canceled most things for tomorrow. So the kids will have had a 6 day weekend.
 
  #32  
Old 01-15-09, 07:04 PM
Member
Thread Starter
Join Date: Sep 2008
Location: USA
Posts: 134
I am in southern California, beautiful 81 degrees here - like summer.
 
  #33  
Old 01-15-09, 07:11 PM
Jarredsdad's Avatar
Member
Join Date: Oct 2002
Location: Troy, VA
Posts: 1,532
Dang global warming will get you every time.

SoCAl is getting ready to fall in the sea or get buried by Yosemite or both.
 
  #34  
Old 01-15-09, 07:20 PM
Member
Thread Starter
Join Date: Sep 2008
Location: USA
Posts: 134
Originally Posted by Jarredsdad View Post
Dang global warming will get you every time.

SoCAl is getting ready to fall in the sea or get buried by Yosemite or both.
Yeah, been hearing that my entire life how California was going to break and fall in the sea.

I remember in the early 70's how people flocked out of California for safer places. Places where a tornadoe comes and picks up your entire house and drops it in a billion little pieces 50 miles away. Places where it snows and you have to get a shovel every morning to get to work. Yeah, I been laughing my ass off all this time.
 
  #35  
Old 01-15-09, 08:13 PM
Jarredsdad's Avatar
Member
Join Date: Oct 2002
Location: Troy, VA
Posts: 1,532
I hear Ya.

Also remember in the 70's when the scientists were trying to warm about global Cooling? Guess that couldn't make as much money.
 
  #36  
Old 01-16-09, 08:23 AM
Member
Thread Starter
Join Date: Sep 2008
Location: USA
Posts: 134
I hear ya too with the climate thing.

Like all the reports showing the ozone hole getting larger and larger and all of the terrbile consequences it was going to bring.

Now that the ozone hole is actually getting smaller and smaller and not bigger and bigger, everyone forgot about the doomsayers.

I can't tell you how many people around here got filthy rich in the 70's buying up all the properties that panic individuals left behind thinking California was going to drop into the ocean.

Obviously it can happen and huge land masses of California may break away, but before I worry about that, I will worry about more realistic and personal things like cancer and nasty health problems you and I are not immune to regardless of where we live. Beer 4U2
 
  #37  
Old 01-16-09, 03:05 PM
Member
Thread Starter
Join Date: Sep 2008
Location: USA
Posts: 134
Originally Posted by Jarredsdad View Post
The IAQ and the VisionPro 8000 has Circ on it. Also fan off delays fro heat and cool.

Component
Nice, but does this thermostat have the option as the one poster said, so tell it to run the air blower at say 1/3 of the time regardless if the need for heating or colling is called for?
 
  #38  
Old 01-16-09, 04:08 PM
Jarredsdad's Avatar
Member
Join Date: Oct 2002
Location: Troy, VA
Posts: 1,532
Yes that's what the circ funtion is.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes