Q&A on how-to, benefits and risks of continuous blower unit fan operation.

This article series explains how and why to set your air conditioning or heating system blower fan to continuous operation in order to improve indoor air quality by increased and continuous indoor air filtration.

Q&A on Why Run an Air Conditioner or Heating Blower Fan Continuously

For maximum indoor air qality (IAQ) improvement in buildings: for a new blower installation we selected a fan unit which had both the capability of delivering adequate CFM of air flow and a blower fan motor duty cycle which permits continuous operation if we wish to run the system that way.

These questions and answers about running an air handler blower fan continuously were posted originally

at BLOWER FAN CONTINUOUS OPERATION - be sure to read that article.

Can I run the blower continuously to help move fireplace warmth to other areas of the home?

When I am burning wood in my fireplace (in my living room, where the thermostat is), of course the fire warms the living room up, but the rest of the house is cold. If I run my fan only, during this time, then will that circulate the warm air through the rest of the house? On 2011-10-23 by Chris

Reply by mod: Fireplace need for combustion air may be making your home colder, not warmer

That sounds like a good idea, Chris except that just how effective the air handler's blower system is at redistributing warmth from the fireplace elsewhere in the home depends on some critical factors.

• Does your fireplace have a direct supply of combustion air?
  
  If your fireplace is not supplied with combustion air from outdoors it's drawing its air supply from the heated areas of the home. In that case the only areas of the home that will actually be warmed are those in front of the fireplace that receive radiant heat.
  
  
• Is your wood burning fireplace really contributing ANY net heat gain to the home?
  
  Watch out: if you're not using an air-tight high-efficiency woodstove, when you burn a wood fire in an open fireplace (for example), that fire creates a significant updraft at the chimney and draws so much building air towards the fireplace that a careful study of your home may find that you're actually making most of the home colder than before: you're drawing cold outside air into the building through various air leak points just to satisfy the air demand of the fireplace.
  
  See these articles for more details:
  
  COMBUSTION AIR REQUIREMENTS 
  
  COMBUSTION AIR for TIGHT BUILDINGS where we state:
  
  

  Typical airtight woodstoves require only 10-25 cfm of combustion air - much less than an open fireplace (50 to 150 cfm or more) or to older non-airtight woodstove. But in tighter homes it may be necessary to provide combustion air or a draft inducer fan even for these appliances.
  
  Also see FIREPLACES & HEARTHS  - starting point for making sure your fireplace is safe and working properly
  
  and HEAT LOSS in BUILDINGS 

• Where is the return air inlet to your air handler and duct system?
  
  If it is quite distant from or remote from the room warmed by the fireplace it may still help to make indoor air temperatures more even but it may take some time to have any effect.

Does running just the fan, not A/C save on electricity?

I am wondering if having the fan on my thermostat ON, but the actual air conditioning, OFF, does that save me power? or am I basically just over working the fan and not gaining any energy saving benefits? On 2011-09-10 by hillary

by (mod) - yes

Hillary, running Just the A/C fan will move air and make for more even temperatures in the home and it will increase the level of air filtration.\

If that is enough to make you comfortable without running the A/C system, it's certainly less costly.

I am Afraid to Run the Blower Continuously Because Air in my house gives me a headache

I have a 1968 solid metal air duct system and 1995 Emerson 3.5ton heatpump.

I bought the house in Austin TX june 2012. It is a fixer-upper. Recently, with cooler weather, when I come into the house, I start tearing, getting a headache, runny nose, and smelling a strong odor which I cannot identify (I am from NY, no mold/fungus/ allergy experience prior to arriving in Austin). Replacing ac system is >>>$$ and would not include air ducts replacement.

I have not seen any mold but in a 1968 abandoned, tenant occupied house, I'm sure there is....need help.

The headaches stop as soon as I go outside. Did not occur until last week (first wk of OCt 2012). Help!!! ivm1@columbia.edu Edgardo, who is your AC contractor? On 2012-10-06

by (mod) -

Edgardo,

See ODOR DIAGNOSIS SIX STEPS - taking an orderly approach to odor source tracking - for help in tracking down odors and smells to their source.

also ENVIRONMENTAL INSPECTORS & TESTING SERVICES may help you find an expert

How can I find out if my fan is rated for continuous duty operation?

How can I find out if my fan is rated for continuous duty operation? Thanks. On 2012-08-12 by Spence

Can my thermostat control the fan for continuous running?

Can or is there a thermostat to control the fan only on a unit?

On cooler days we open the windows however our house does not circulate air well on its own so we turn the fan on and let it run to circulate air.

Is it possible to say get a programmable thermostat that can run the fan only say for 15 minutes, or some other programmable time, and have it run say every 90 minutes or some other time programmable of course. On 2012-08-12 by DavidD

Answer by (mod) -

Spence and David D there is no reason at all why a thermostat can't be used to control the fan in a duct system - just ask your HVAC tech to wire it up for you. Instead of calling for heat, the thermostat can simply turn the fan on or off at a given temperature range.

The rub may be that no matter how long the fan runs it won't, in some conditions, cool the house enough for the thermostat to ever tell the fan to turn off. For this reason, most folks simply manually turn the fan on and off when they want it to operate.

In fact there some attic vent fans that work this way, though as I explain next, those can pose a fire hazard.

We don't want a themostatically operated attic fan or whole house fan without some special fire safety controls as in event of a fire we wouldn't want that fan to come on and increase fire draft.

Pinging noise in the air ducts stops when we switch our blower fan from AUTO to ON

Last night we were awoken by a pinging noise coming from the vents that stopped as soon as we clicked the fan switch to on.

When we switched back to auto the ping noise happened again. It sounds like something is broken somewhere in a damper or something. Anyone know what could cause this? On 2012-08-05 by Rob

Advice by (mod) -

Rob, if you heard the vent/duct noise when the equipment was not running then it's probably not the equipment itself but perhaps duct noises that occur due to a temperature change (cooling night air, shrinking sheetmetal).

by Rob - I think the noise is coming from a zone damper

It sounds more like the Auto setting is sending Open and close signals to the zone damper and the zone damper is stuck or something and gives off a rythmic ping 1 2 ping 1 2 ping etc.

Also, I have noticed condensation water splashing out from around the white drain pipe, almost like the drain is clogged and water is trying to find a place to go.

I think something shorted out from the water maybe?

by (mod) - check and free up a stuck zone damper

Rob

Interesting. I suppose thermostat contact bounce or a bad heat anticipator or bad TT could be at fault - I'd try removing the TT wires from the TT and tying them together to call for cooling - if the system runs ok then we know it's the thermostat. If the problem continues it's the TT wiring or a control board.

And of course check out and clean/free up that zone damper.

 

Why would the air handler blower shut off at night?

Why does my continuous fan opration shut off over night? On 2011-09-07 by Charlie

by (mod) -

Sorry Charlie, I can't guess. See if you can dig up the model and serial number of your equipment, then take a look in the installation and operation manual there. Or is your thermostat a programmable one that is turning off the fan?

Our A/C doesn't cool upstairs and our house is too humid

In the summertime, our R.H. reached 70%.

It was so bad, that the moisture from the (many) showers we take condensed from the air onto two INSIDE WALLS, with drip marks flowing down the walls. We will be installing vents in our two upstairs bathrooms in the next few months, which I believe will make a big difference.

However, in September we purchased a dehumidifier to put in the hallway between the two bathrooms.

With it running 24/7, we couldn't get the R.H. below 60%, on all three levels of the house. Even now, when we have our heating on, as soon as the temperature outside warms up a bit, the humidity in the house shoots up.

Three major problems we have: Our air conditioner doesn't cool the upstairs (other floors fine), we only have one return vent upstairs, and since we installed a high efficiency furnace, the moisture problem has definitely gotten worse.

I want to install a central dehumidifier, but we have a TRANE furnace and I've been told that only the same brand dehumidifier can be installed.

Is that true?

And is it true that only having one return vent upstairs will prevent the dehumidifier from being effective upstairs? I know this is a lot of information, but we're getting desperate. On 2011-11-27 by Nancy

by (mod) -

Nancy, if your A/C system is not cooling AND presuming that your air flow is not restricted by a clogged filter, crushed duct, dirty blower fan or coil, etc., then it's possible that your A/C system is not properly sized for the home.

Combined with that problem if your building has a source of excess moisture (wet basement or crawl area, lots of steamy showers, poor exhaust venting, pasta cooking, large number of occupants, etc), a portable dehumidifier may lack the capacity for the total space you have combined with the moisture source.

Frankly I would never expect a portable dehumidifier placed in a hallway to be capable of dehumidifying an entire multi-story home. It just can't move enough air through itself and won't pull from nor deliver air to the more remote rooms.

I agree that undersized ductwork or inadequate return air can severely limit the capacity of your central A/C system.

I'd have an expert examine the HVAC system entirely: duct system, blower unit, cleanliness, air filter condition, type and location, etc. before making any costly changes in the system. It seems odd to me to be considering adding a "dehumidifier" to an existing HVAC system that already has air conditioning.

Properly sized and installed, the air conditioning system should be doing the dehumidification.

Finally, a thorough inspection of your home for moisture sources, leaks, etc. sounds needed as well.

Nancy - be sure to see the article titled DEHUMIDIFICATION PROBLEMS for a step by step guide in fixing this problem.

...

Continue reading at BLOWER FAN CONTINUOUS OPERATION - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• BLOWER FAN OPERATION & TESTING
• FAN WONT STOP - LIMIT SWITCH
• FAN WONT STOP - THERMOSTAT SWITCH
• AIR HANDLER / BLOWER UNITS - home

Suggested citation for this web page

BLOWER FAN CONTINUOUS OPERATION FAQs-2 at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

Or see this

INDEX to RELATED ARTICLES: ARTICLE INDEX to AIR CONDITIONING & HEAT PUMPS

Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia

Ask a Question or Search InspectApedia

Try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Note: appearance of your Comment below may be delayed: if your comment contains an image, photograph, web link, or text that looks to the software as if it might be a web link, your posting will appear after it has been approved by a moderator. Apologies for the delay.

Only one image can be added per comment but you can post as many comments, and therefore images, as you like.
You will not receive a notification when a response to your question has been posted.
Please bookmark this page to make it easy for you to check back for our response.

---

 

IF above you see "Comment Form is loading comments..." then COMMENT BOX - countable.ca / bawkbox.com IS NOT WORKING.

In any case you are welcome to send an email directly to us at InspectApedia.com at editor@inspectApedia.com

We'll reply to you directly. Please help us help you by noting, in your email, the URL of the InspectApedia page where you wanted to comment.

Citations & References

In addition to any citations in the article above, a full list is available on request.

---

ADVERTISEMENT

---