Thread Number: 76145  /  Tag: Other Home Products or Autos
Central AC and Closing Interior Doors
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Post# 999796   7/9/2018 at 10:38 by mark_wpduet (Lexington KY)        

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From the website:
Always keep all of the doors open when running central air conditioning. Central air runs off a blower fan and the system is balanced for whole-house cooling. Closing a door unbalances the system, causing pressure changes that suck hot air in from the outside and bleed cold air through leaky air ducts on the inside. Your central AC runs longer and works harder to compensate with these conditions when a door is closed.

Anyway - This leads me to this question. In my house, there is one door that we have to keep closed (it's a spare bedroom with stuff in there and the cat is not allowed in that room), but the rest of the doors are opened, except for the master bedroom closet. There is a vent in that closet, would that mean I need to keep that door open as well?

Post# 999799 , Reply# 1   7/9/2018 at 10:56 by Yogitunes (New Jersey)        

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to a point, they are correct, and you would most likely have to keep that door open during the A/C setting....

as our unit in the country house is down on the far side of the basement, the other side doesn't get the full cooling effect, figuring on closing or tempering down rooms in order to force more air to the other side of the house....

the thing is, it threw my unit into havoc, run longer, and it would freeze the tech instructed, we opened everything back up, unit runs fine....

we could close bedroom doors at night, where the unit didn't run as much, just not something to do all day long...

I use to install those 3M Hepa filters, they worked well, but filled up fast, which slowed down air flow, this also caused the unit to freeze those are saved for the winter months only......the regular blue ones work great if you spray them with Lemon Pledge or Pam cooking spray, and change them often as they will attract dust quickly....

Post# 999805 , Reply# 2   7/9/2018 at 11:41 by neptunebob (Pittsburgh, PA)        
But you shouldn't have to do that...

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Each room in a house with forced air heat and AC should have both a supply grille and an return grille, except the bathrooms have just a supply to keep the odors away from the rest of the house. Closing door should not make any difference if there is properly installed ductwork.

Post# 999826 , Reply# 3   7/9/2018 at 14:41 by DADoES (TX, U.S. of A.)        

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Typical design here is supply registers in each room (one or more depending on room size) and one central return in a hallway or some such ... not a return in each room.  Returns also depend somewhat on size and layout of the house.  I have one system, two returns -- one at each "leg" of the L-shape.

Post# 999829 , Reply# 4   7/9/2018 at 15:54 by appnut (TX)        

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I have one air return right in the center of the house and only one air register per room.  One bedroom door stays closed most of the time because it tends to be the catch-all room. 

Post# 999832 , Reply# 5   7/9/2018 at 16:12 by Launderess (Quiet Please, There´s a Lady on Stage)        
Responses pretty much nailed things down

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Central (forced) eating or cooling for that matter in principle has not changed much since days of those huge old "Octopus" or whatever furnaces that sent hot air up into buildings. Things depend upon the free flow of air circulation. If or when that does not happen, often units can or will make their displeasure known.

Cannot say have ever seen a home or apartment with central heating and or air return registers in every room. Vents for incoming cool or hot air yes, but not other way round.

Now with through the wall or window AC, yes, you can (and maybe should) close doors to unused or whatever rooms to lessen the load. This or the opposite; use of fans to help move cooler air/improve circulation.

Post# 999835 , Reply# 6   7/9/2018 at 16:32 by Yogitunes (New Jersey)        

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well, I do have return vents in all rooms except the bathroom, they are located up high....

my MIL has a unique setup, return vents in all rooms, but located at the ceiling and below at the floor, theres a tiny servo motor driven vent that controls where the air is pulled from......during the winter it pulls air from the floor level, during the Summer A/C mode, it pulls from the ceiling level...theres also a variable speed blower....

also a Dehumidify Mode, turning on both the heat and A/C...found this to be excellent on rainy days....

what I like too, is all levels are the same temp, keeping the basement area equal to the top floor

Post# 999837 , Reply# 7   7/9/2018 at 16:36 by Launderess (Quiet Please, There´s a Lady on Stage)        

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How interesting Yogi.

Did you add these return vents after system was installed, or did you plan things that way?

Post# 999847 , Reply# 8   7/9/2018 at 17:18 by washman (Butler, PA)        

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I only have 2 bedrooms however I have a supply vent in my master bathroom AND the walk in closet. I keep the doors open all year long.


The rest of the layout is "open floor plan" so the living room/dining/kitchen are pretty much all one area.


Bed 2 has 2 return air, master bed has 2 return air, hallway has 2 return air and in living area 2 large return air grills are supplied.


Needless to say, air circulation is quite robust with this setup.

Post# 999848 , Reply# 9   7/9/2018 at 17:26 by CircleW (NE Cincinnati OH area)        

The HVAC system in my house has return air intakes in all the bedrooms, and one large return in the hallway for the living and dining rooms.

Another thing is it depends on how many separate HVAC systems the house has. My cousins in TX lived in a house that had 5 units (it was a very large 2 story house), and they would close off the rooms upstairs, and keep them warmer in summer and cooler in winter if they weren't being used. Also, some systems are zoned with dampers.

I think it is a good idea to have the HVAC system tied into the fire, smoke & waterflow detectors, so that the air handler will shut off in case of fire. You can also get doors equipped with a release that will close them if the fire alarms are activated. This will drastically cut down on heat and smoke damage if a fire occurs.

Post# 999860 , Reply# 10   7/9/2018 at 19:39 by fan-of-fans (Florida)        

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I've noticed with a lot of newer houses, that the bedrooms have equalizer vents, either one above each door that lets the air pass through the wall back to the hallway, or one on the ceiling that is connected with a duct to another vent in the hallway.

This allows the air flow to be equalized when the doors are closed. Not sure if this is a code requirement or not. Hadn't really noticed it until the last 10 years or so, although I have seen the vents above doors in mobile homes further back.


Post# 999861 , Reply# 11   7/9/2018 at 19:44 by Launderess (Quiet Please, There´s a Lady on Stage)        
Don't know if this applies to current conversation

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But was brought up to always sleep with bedroom doors closed (and a window cracked open) as "in case of fire) or whatever.

If you notice in old films or other media people and even children/infants are always sleeping behind closed doors for most part. If that arrangement affected airflow from central heating/cooling then something would have to give one suspects.

Post# 999870 , Reply# 12   7/9/2018 at 20:51 by Yogitunes (New Jersey)        

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no, all this stuff was already installed....just took a while to understand how it all worked...

remember homes and/or apartments that had sort of a vent window above the doors...the front door usually was frosted, with the number of the Apt/house....all interior rooms were clear glass, never knew how they tilted, just that some were open and others closed, never thought about how these would be used for temp adjustment per room...

Post# 999871 , Reply# 13   7/9/2018 at 21:21 by Launderess (Quiet Please, There´s a Lady on Stage)        
Yes, recall those as well.

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They are called transoms and at one time were very popular for indoor doors and or above entrances into apartments or whatever.

Idea behind transoms was in days before AC one could have closed doors (interior or otherwise), but still have ventilation. More so if you opened windows.

IIRC they are outlawed in New York and most other areas by code for new construction due to being a fire hazard. Well at leas the ones which open, fixed transoms are another thing.

Ordinarily if a door is closed (and especially if it is fire proof) it will contain a fire and good amount of smoke on the other side. OTOH if the fire is elsewhere a closed door prevents smoke (which is the main killer in a fire) from getting into a room/apartment. Transoms obviously defeat that purpose if door is closed but they are not.

You can still find transoms in some of the older buildings here in NYC (and we have plenty). Some have been painted over and or sealed, others still work as intended. These would be above interior doors only. IIRC all such devices above doors that lead into apartments or offices have long since been sealed or removed (see above).

Post# 999872 , Reply# 14   7/9/2018 at 21:21 by Xraytech (S.W. Pennsylvania, near Pittsb)        

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My central air has 1 supply vent in each of 3 main floor bedrooms, the bathroom, kitchen, and 2 in the living room.
I have 2 return air vents, 1 in living room and 1 in hallway.

All my doors are left open, except for door 2 second floor where there are no air vents. I close the bedroom door while sleeping, and the other bedroom gets closed when receiving company as it’s the catch all room.

Post# 999891 , Reply# 15   7/10/2018 at 06:47 by mark_wpduet (Lexington KY)        
My house

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isn't very large. It's a single story 1375 sq ft 3 bedroom 2 baths. In the middle hall, there are two (I guess they're called intakes?) One on the wall and a smaller one on the ceiling. I keep the filters super clean. That's the only intakes in the entire house. I've never lived anywhere where there were intakes in each room of the house. But closing the master bedroom door definitely is less efficient, at least during the worst parts of the day, especially if it's full sun out. It doesn't seem to matter during the night where there's no sun at all.

On very hot/humid full sun days, my AC will maintain 71, possibly jumping up to 73 if it gets past the mid-90s F. But let me close that master bedroom door during that part of the day and you can feel the house slowly warming and the Tstat will jump up as well.

Post# 999972 , Reply# 16   7/11/2018 at 00:24 by tolivac (greenville nc)        

My house has two intakes in the hallway-no intakes in the rooms.Never seen that in a house-do see it in commercial office buildings.My old Lennox still chugs along!I leave all the doors open-gives best efficiency with a central system.

Post# 1000166 , Reply# 17   7/13/2018 at 07:57 by askolover (South of Nash Vegas, TN)        

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My house, MIL's house, parents' house, best friends house all only have one air return in the hallway.

Post# 1000174 , Reply# 18   7/13/2018 at 13:25 by RevvinKevin (So. Cal.)        

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I had never heard of having an air "return" in each room, at least not in a residential setting anyway.


I did see equalizer vents between rooms in a few homes some years ago, thinking that was odd back then because I didn't get the purpose.  Now I get it.


My house is just under 2200 sq ft, all on one level.  When I had the central HVAC installed, I had them install two supply vents in the master bedroom rather than one, being it's a larger room with a 12 foot vaulted ceiling.   For the air returns, they wanted to put one really large one in the hallway near the bedrooms, but I asked them to split it into two and put another one towards the front of the house as well.  The idea being the HVAC would draw in return air from each end of the house. 


I have always slept with interior doors open, but my other half isn't comfortable with that, so now they're all closed at night.   Being there is so much air flow to the bedroom, with the running the A/C at night, I'll prop the door open 5-6 inches, with something on each side of the door so it won't move.  If I don't do that, will slam the door shut when the A/C comes on.  Obviously this can be unnerving if you're sleeping or nearly asleep.   


Otherwise I keep the registers and doors closed for rooms that are rarely used in an effort to reduce cooling load and costs. 

Post# 1000176 , Reply# 19   7/13/2018 at 13:27 by washman (Butler, PA)        
I'll post some pics

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of the air returns when I get a chance.   The airflow in my abode is quite robust and now that I have kicked myself to the garage to light up, smells a whole LOT better.

Post# 1000200 , Reply# 20   7/13/2018 at 16:50 by superocd (PNW)        

My home has air returns in all three bedrooms, the living room, the upstairs hallway and the kitchen. Only the bathrooms and the laundry (which contains the furnace) lacks return air. Ironically, the very HVAC company I now work for installed my HVAC when my house was built in 2004, nine years before I bought it and eight years before I started working for the company.

When my company does a new install, we insist on having multiple return-air inlets throughout the home, ideally in each bedroom in addition to the living room, dining room, etc. It really helps with efficiency, equalizing indoor temps, proper dehumidification when running the AC and much better indoor air quality.

We actually take the time to calculate for the optimal balance of supply and return. You want to have about the same CFM for supply and return. We factor in the blower CFM of the furnace or AHU, and even factor in frictional losses that system components impose (everything from registers to dampers to the air cleaner to the linear run of the system, including bends) to get the proper size of the trunks (the main run for supply and return).

Based on what I've seen in existing installs when doing a repair or replacement, a lot of HVAC contractors seem to only size the equipment, sometimes you're lucky if they even do that properly. The distribution seems to be an afterthought in a lot of cases.

Post# 1000201 , Reply# 21   7/13/2018 at 16:55 by vacerator (Macomb, Michigan)        
air returns

in each room are most common in colder climates and houses with basements.
In the 80's, houses began being "prepped" for central a/c with a return near the ceiling in the main living space, and master bedroom.

Hot weather tip for basement houses; In the morning, open the air filter cover on the furnace for just a minute or so with the blower only on, and blow the cooler air upstairs. I also open my humidifier air damper slightly to recirculate some conditioned air into the blower plenum beneath the evaporator coil. Helps cool the blower motor too when it's running on high speed for a longer time.

Post# 1000202 , Reply# 22   7/13/2018 at 17:02 by IowaBear (Cedar Rapids, IA)        

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My 3 bedroom 1400 square foot ranch (plus basement) has air return ducts in every room but the kitchen and bathroom.


For all that, one side of house is still a lot warmer than the other in the winter.  I suppose I could adjust the airflow to even it out with enough effort and experimentation.


What the house really needs is more insulation in the walls.

Post# 1000209 , Reply# 23   7/13/2018 at 17:57 by DADoES (TX, U.S. of A.)        

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Returns in each room surely improves performance (when doors are closed) but is not a common thing in this area.

I have two supply registers in the master BR, one in the master bath main area and another in the toilet "cubicle, one each in the split walk-in MBR closet.  Two in the living room (or three), one in the kitchen (or two ... depends on where one considers the split between LR and K).  One each in the dining area (which is almost part of the kitchen) and the laundry room and office room.  One in each of the other two BRs, one of which has a larger walk-in closet with a register.  One in the half-bath.  Three (one in each section) of the jack-and-jill bath for the two spare BRs.  Lacking registers are the kitchen pantry and the smaller walk-in closet for one of the spare BRs.

So that's 20 supply registers.

Returns in the small hallway between the LR and MBR, and in the longer hallway outside the two spare BRs.  Both take 25" x 20" filters.

The spare BR wing is 2°F to 3°F cooler (or warmer) than the MBR end.  The master bath is warmest (and coldest) due to three large glass-block windows and being the farthest airflow run.

Post# 1000215 , Reply# 24   7/13/2018 at 18:26 by mark_wpduet (Lexington KY)        

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why have I never seen this? Maybe I just haven't paid attention. I just never remember being in a home that had multiple returns in every room like that. Then again, if I visit that's not really something I'm paying attention to. I'm imagining that's a pain too to change all of those filters. Hopefully, they are all the same size filters if there are that many intake or return or whatever they are called. I know in my hall where the 2 returns are, they are both differently sized returns so I have to buy 2 different sized filters. I'm trying to imagine that same scenario all over the house in each room. What a pain that must be.

Post# 1000222 , Reply# 25   7/13/2018 at 19:16 by appnut (TX)        

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My house is 1565 or so sq. foot rancher.  One air register per room.   I have two air return "grills"--a larger one in the den next to the door into the entrance hall and that air return also butts up to the utility closet in the garage that houses the air handler and water heater.  Then there's a smaller air return grill in the entrance hall perpendicular to the one in the den. 

Post# 1000224 , Reply# 26   7/13/2018 at 19:48 by IowaBear (Cedar Rapids, IA)        

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No air filters on all these return grills.  Just a single "Aprilaire Space-Gard" filter that sits between the air return duct work and the furnace.


It takes one large 25" x 20" x 4" $30 filter that I change twice per year.  These are fairly common around here.



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Post# 1000229 , Reply# 27   7/13/2018 at 20:19 by Yogitunes (New Jersey)        

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for me, there is only one filter, in the heater itself.....

there are little filters you can buy that fit behind the grill for even more filtering, I guess it would help keep the duct work cleaner...

theres also return air grill covers, their magnetic, never thought that I could close off return lines, and make the unit pull air from warmer rooms needing more cooled air...I wonder if that would put the system into havoc like when I closed off regular vents....

Post# 1000298 , Reply# 28   7/14/2018 at 17:05 by jerrod6 (United States of America)        

I have a three story house with all of the bedrooms on the second and third floors but only one HVAC system. There are returns in each hall way on each floor. There is one return and two supply vents in the living room.

Every bedroom has a return high up over the door, and the master bedroom has two supply vents and two return vents. The return vents in the master bedroom are placed so that one is near the floor and the other is near the ceiling.

In the summer I have tried leaving everything open and also closing the bedroom doors. What happens is that if I close the bedroom doors, the bedrooms get very cool, but they end up the same temperature as the rooms on the first floor so this works out very well.

If I leave all of the doors open the entire house will level off to a temperature but because the the bedrooms are on the upper floors they become warm because the cold air is escaping into the hallways.

If you are in a single level house with few returns it is probably best to leave everything wide open to help with circulation.

I did another thing by accident but it turned out well. In the fall I opened all of the return vents as far as they would go to clean them, then I forgot about it. A few months later I turned the heater on and found that there is much more supply air coming out of the vents so it seems like if you have adjustable return vents it might be better to leave them wide open to improve the flow of supply air.

Post# 1000329 , Reply# 29   7/14/2018 at 21:38 by fan-of-fans (Florida)        

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My house is right at 1400 sq ft. Have one vent in each bedroom, bathroom, two in the kitchen (one over the main kitchen and one over the dining area), two on the wall in the living room and one in the laundry room. The laundry room one is closed off all the time and the air handler is in there. The return grille is in the hallway, funny thing is at night, you can see a funny colored light through it because of the UV lights in the air handler. I always thought it was the LED night light we got reflecting off the vent louvers but it's actually those UV lights.

I haven't seen houses with a return in each room either around here.

Post# 1000417 , Reply# 30   7/16/2018 at 12:29 by CircleW (NE Cincinnati OH area)        

I think the placement of air returns depends on the individual HVAC contractor, and what they are used to doing if something else is not specified by the owner or architect. The house my cousins lived in (that I mentioned above) was custom designed and built, so every detail was specified as to how it was to be done. I know the place was very expensive when they built it in the mid 80's - over $500,000. I wouldn't expect houses built for the market to include anything that would add to the cost.

Post# 1000463 , Reply# 31   7/16/2018 at 19:37 by Streakers (Columbus OHIO!)        
My home - built in 2004

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two storey with a full basement - 4 bedrooms, has return air vents in all four bedrooms upstairs and two large return air vents in the living room and and the study on the ground floor.

Only one large filter which is in the basement on the return duct just before the blower fan itself. It's a Trane Unit both inside and out and keeps the house (over 2200 square feet not including the basement) comfortable both in heat and cool modes...

The return air vents upstairs in the bedrooms are however located up high, the returns downstairs are located at floor level. Upstairs, up high, I'm assuming to help draw the high, warmer air down back into the unit during the summer months to help improve airflow with cooling mode etc. - and I know that when in Air Con mode the blower does run at a higher speed. (Must be a two stage unit?) There are air vents in the basement as well - and has enough power cool the basement comfortably - but not necessarily heat it as the vents are at ceiling level only.

I have installed a NEST thermostat so I can have some more flexibility when I'm not at home and for scheduling etc.

But larger rooms have more than one vent - master bedroom has three in total for example, living room has multiple etc...

Does the trick! I just figured most newer build homes would be all like this? Seems logical to me with convection from heating and and cooling modes - hot air rising and cold air sinking etc??

Those that don't have return air vents in those rooms - do you have trouble with hot/cold rooms - and if you do - how do you combat that?

Post# 1000465 , Reply# 32   7/16/2018 at 19:54 by GusHerb (Chicago/NWI)        

It’s standard practice around here in the Midwest to install a return in each room. Down south it’s standard practice to have one central return in the hallway, primarily to cut costs, reduce amount of ductwork in the hot attic and I suppose a return in each room isn’t as crucial for cooling as it is for heating, though I find that arguable. We have two systems here, one for upstairs and one for downstairs. Downstairs system has sheet metal ductwork in the basement and upstairs system has flex duct in the attic. Both levels have high/low returns in the walls, plus I had a return added to the ceiling in each room when the upstairs system was replaced because the return side of the system was starved for air.

Post# 1000467 , Reply# 33   7/16/2018 at 20:23 by washman (Butler, PA)        
Photos of my return vents

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1047 SQ slab-on-grade home with 2 Ton Goodman AC and 60,000 BTU Goodman furnace.


In living room photo with TV, the bottom return air vent is to the left of the fan.


Attached vid of the Goodman running in August of 2015


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Post# 1000491 , Reply# 34   7/17/2018 at 06:19 by vacerator (Macomb, Michigan)        
I guess apples

and oranges for heating with the air returns near the ceiling. Heat rises, so the furnace gets warmer air rather than colder off the floors. Reaches heat exchange temp. faster?
You can tell when a guy is single when a wire or cable is in plain sight on a wall. Not that it's second class or anything. A friend once strung Christmas lights on his Nordic Track. He's not the best house keeper though. Says no one see's his mess. But after remodeling with nice Kitchen Aid appliances, and antique brass light fixtures and all?

Post# 1000493 , Reply# 35   7/17/2018 at 06:29 by tolivac (greenville nc)        

If the single person is living in a rental place-than the wires in sight are really OK-he or she doesn't want to damage building walls that don't belong to them.The habit carries to this day with me!

Post# 1000503 , Reply# 36   7/17/2018 at 10:25 by washman (Butler, PA)        
Just haven't

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got around to cleaning up the cable.  Someday.........I will get something lined up where it is a tad more presentable.


Until then, I am digging OTA and Netflix and not missing the exorbitant cable TV bill.

Post# 1000508 , Reply# 37   7/17/2018 at 11:34 by iej (Ireland)        

I would assume it very much depends on how your system is designed. A proper system should be able to function with the doors closed by having air inflow and outflow in every room.

I remember working in a university where a room had been divided up with partition walls to create lab spaces, without any reference to the air conditioning design. It ended up with one room barely getting any flow and the other two were often freezing as it screwed up the system's ability to pick up temperature readings. So it was opening dampers and flooding one partition with very cool air all the time.

After a lot of complaints to facilities they eventually added the necessary ducts and stats.

Post# 1000556 , Reply# 38   7/17/2018 at 17:15 by appnut (TX)        

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Steve, is your heat source natural gas and not electric or heatpump?  All 3 houses I've owned (gas & heat pump systems) the blower was specifically set to run slower when heating vs. higher speed in AC mode.  It's probably not a 2-stage system.  If it were, the blower would be more variable in speeds than just the 2 you've noticed. 

Post# 1000641 , Reply# 39   7/18/2018 at 08:26 by chachp (Conway, AR)        
Only one return in my house

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My mom’s house was built in 1969 and it had a vent on the floor in every room that supplied the cool air and returns up by the ceiling in every room.  I remember my Dad used to play with the dampers in the basement when seasons changed.  He eventually took a marker and indicated where each should be for Cooling and then for Heating.

I’m not sure if any of those dampers controlled the returns in the rooms.  I just remember he had an HVAC guy there a couple of times to help him work through it all.  We switched those twice a year religiously and it seemed to keep the house comfortable. They had a large ranch (about 3,500 sq. ft) with two units.

Our new house is a 2,500 sq. ft. ranch.  We have only one return towards one end of the house.  We have a zoned system in this house and I still don’t quite understand how it is supposed to work.  My office is on one side of the house and the Master on the other.  When I switch on the thermostat in the Office it reduces the air to the Master.  I had the guy here a couple of weeks ago and he talked a lot about pressure and returns and quite frankly it went over my head.  We agreed he would come back when it’s not so warm upstairs (our unit is in the attic) and investigate.  I guess all the runs have dampers in them and he has to observe how they change as the system calls for different things.

I work from home, so I switch it on during the day and in the afternoon I switch it off.  The house is pretty well insulated, so it stays very comfortable.

We’ll see what he says. Does anyone have experience with a zoned system like this?

Post# 1000736 , Reply# 40   7/19/2018 at 10:29 by drhardee ( Columbia, SC)        
Transom windows

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Ahh, transom windows. They're very common in older homes in the south, where they provide an important source of air movement from room to room. Our home, built in 1947, has four or five of them, including the hall bathroom.

We keep them open year around; but if we have guests, we'll advise them to close the guest room transom if they're going to be "noisy" in the night...

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Post# 1000757 , Reply# 41   7/19/2018 at 16:30 by CircleW (NE Cincinnati OH area)        

I'm very surprised to see transom's in a house built as late as 1947. Around here you don't usually see them in buildings constructed after the teens. They add a nice touch to your attractive home.

Post# 1000769 , Reply# 42   7/19/2018 at 18:38 by Streakers (Columbus OHIO!)        

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My heat source is natural gas. And from when I had the HVAC serviced last - the bloke tells me that it's only got two speeds - and I've only noticed it ever run at two speeds...

I could be wrong...?

Aaaaaaaand - those speeds are not adjustable through the Nest either - they're preset through either Heating or Cooling mode... Kind of strange...

If/when I ever have to upgrade it - I will be getting a unit with far more flexibility with fan speed options - if there is such a thing though...

Hope that helps...


Post# 1000775 , Reply# 43   7/19/2018 at 19:15 by appnut (TX)        

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Steve, yes it helps.  As I believe I've stated, I do have  variable speed air handler.  I also have a multi-stage compressor for both the AC function as well as the Heat Pump (heat portion--which is actually one-in-the-same).  I remember from all the previous years with central air, the fan motor speed was controlled by dip switches set at the time of installation according to guidelines.  Combo52 is the individual responsible for providing me the information at a wash-in in 2002 resulting in me selecting the system I have currently. 

Post# 1000777 , Reply# 44   7/19/2018 at 19:33 by DADoES (TX, U.S. of A.)        

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Most interior HVAC blowers have multiple speeds.  Non-variable speed units are hard-wired to a specific speed, usually higher for cooling and lower for heating.  Changing the speed can be done by switching the appropriate wire connection(s) .... the installer selects the correct speeds for the required cu ft/min airflow rate.  My system runs the same speed for both cooling and heating (heat pump).

Post# 1000897 , Reply# 45   7/21/2018 at 01:35 by tolivac (greenville nc)        

One guy here at work had the variable speed blower motor--had it replaced with a two speed one when the variable speed motor died.The new variable speed fan motor was going to cost almost $600-the two speed one cost less than $300 from Grainger.The circuitry in the variable speed motor was sealed in epoxy-you couldn't repair it.

Post# 1000907 , Reply# 46   7/21/2018 at 06:23 by DADoES (TX, U.S. of A.)        

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Variable-speed (ECM) blower motors are very expensive.  My understanding is that they vary the speed to maintain a specific (set) cu ft/min airflow rate for low, med, high, whatever recirculation speed is called, to compensate for variations in ductwork design and 'obstructions' such as filters.  Is that right or am I misunderstanding?

Post# 1000909 , Reply# 47   7/21/2018 at 06:39 by tolivac (greenville nc)        

The variable speed fan motors were for energy saving-if the cooling or heating conditions don't require a full airflow the motor would be cut back in speed saving power.In theory this sounds good but really doesn't work out as we see these variable speed motors replaced with fixed speed versions.The cost doesn't pay off for the little energy saving you may get.Thecircuits in those motors fail often-unless they have been improved.And it seems like any other piece of HVAC equipment it fails when its scorching hot outside or blustering cold.Also some HVAC systems have variable speed compressors.Don't know the failure rates on those.Imagine it would be steep in cost!!

Post# 1000910 , Reply# 48   7/21/2018 at 08:01 by DADoES (TX, U.S. of A.)        

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I had a Lennox 2-speed heat pump system with variable/ECM blower at my previous house.  The blower motor failed (during warranty!) in a way that caused it to run backwards.  This was in the early 2000s.  I was told it would been $600-something (or maybe it was $800-something) if not in warranty.

On the other hand, my current house has a single-speed heat pump with what I assume is a non-ECM/non-variable blower (it runs at the same full speed for both heating and cooling).  Blower motor failed on it at 7 years.  The cost was $664.  Flat-rate, non-itemized invoice so I don't know what was the breakdown for part vs. labor vs. diagnostic, blah-blah-blah.  I told the HVAC servicer in no uncertain terms that the charge was outrageous.

Post# 1000919 , Reply# 49   7/21/2018 at 11:29 by washman (Butler, PA)        

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Which causes me to question why the love affair with these so-called energy efficient HVAC systems when a simple motor replacement often wipes out whatever savings you may have obtained energy wise.  And if you really want to take it in the shorts, try replacing a control board or defroster board.


Even more absurd is the fact most if not all of these motors are sourced from China or Mexico. Neither is a haven for expensive labor so what gives?

Post# 1000939 , Reply# 50   7/21/2018 at 17:32 by vacerator (Macomb, Michigan)        
It's all about the economy of scale

in profit, and investor market dividend.
Cheaper labor, higher profit, higher dividends. So investors are fine with the risk of repair or replacement because they make incremental dividend's on their portfolio, pension plan, or 401k.
Yes, the repairs are expensive, but with a 2 stage variable speed Lenox for example, at least includes a ten year parts warranty. A non heat pump 2 stage variable speed furnace costs at least $3,500.00. No doubt, one repair wipes out any energy savings.
Inducer motors are also frequent repairs.
Fasco was among the worst some time ago. Now I don't know.

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