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  1. #1
    Join Date
    Sep 2004
    Location
    Round Rock, TX
    Posts
    25

    Master Bedroom Always Colder

    Hello,

    I'm trying to diagnose a problem, but don't know where to go from here.

    Situation:
    Master Bedroom is always 5 degrees colder than rest of house. We've only been here two years, but it seems to hold true in both heating and cooling season. I run the system in continous fan mode, if I turn this to "auto" the temperature difference is usually 8 degrees.

    I have a 1.5 story house, (Two separate HVAC systems, one for each floor) the room in question has attic space above (insulated). The master bedroom has a large window on it's exterior wall, which gets moderate shade from trees, and faces NE (Austin, TX)
    The original duct plan had a large return in the master bedroom and another bigger one in the hallway outside of it. I had dedicated returns added to most doored rooms in the house (excepting bathrooms, closets, and the utility room). So the Study, and 2 other bedrooms have dedicated returns).
    I have this feeling that they didn't balance it right, but if that were the problem wouldn't I notice something along the lines of that room being too hot in one season and too cold in the other? I have this thought that too much air is being "sucked out from this room, both from the return in this room and the one just outside of the door (originally designed to service the whole downstairs except for the master). There is a 3/4" to 1" undercut on the door.

    Random Data:
    I bought from a semi-custom builder. So the system was modified from the stock plan. This was not a retrofit. well, at least it was all installed at once
    The utility room for example when in heating mode gets noticeably warmer than the rest of the house. (no return in this room, door shut, it makes sense), but not the master bedroom.
    Attached is a scan of this part of the house. I drew in the returns (not to scale)

    Ductwork are flexible insulated (R6) ducts.
    Any thoughts?
    Attached Images Attached Images  
    Last edited by mettius; 04-07-2007 at 01:56 AM.

  2. #2
    Join Date
    May 2006
    Location
    east central indiana
    Posts
    1,117

    A few questions

    >How many supply registers in this room, and what size pipe to each?
    >Manual (or even automatic) volume dampers present at the take-offs from the duct?
    >Length from furnace, and length of run-outs to these registers in the room?
    Flex or metal pipe? Extreme bends?

    I see from your other post that you have a CVA. My suspicion is that this has something to do with how the variable speed motor calculates duct static and rpm's. I think it's just not pushing enough air to that room in heating mode. But with cooling speed being a higher rpm, it does not have this problem then.

    If you could some pictures of the ductwork and the run-out(s) that supply that room, it might be helpful.

    I think your return situation in that area is probably okay.

    But according to one guy on here, I don't know squat about duct. So maybe you oughtn't listen to me.
    This space for rent.

  3. #3
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    5 cooler ,heating and cooling,makes me think the required cfm for cooling is much less then need for heating.

    However as 41530 pointed out,your system likely has differnttotal cfms for heating then cooling.

    Posting model numbers would help.


    You have a Thermidistat,which is a great control,however there's a lot to do with air flow ,in the dip swith settings,19 or more steps to configure it ,and jumpers to be removed or left in place.I'd suspect something is wrong there.

    Info. may be available on settings at www.commercial.carrier.com

  4. #4
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,086
    Some general thoughts/questions:

    Any recessed (can) lights in the master bedroom?

    Utility room is warmest due to having no outside wall exposure. Master bedroom is coldest due to having what appears to be the largest outside wall and window surface area among all bedrooms (master bath is included since it adjoins master bedroom) and either not enough supply air, or an imbalance between supply and ducted return, causing room air pressure to go negative when door is closed, creating infiltration of cold, outdoor air into master bedroom through any gaps in construction.

    Does supply register blow its air toward the wall with the large window (known as "washing" a wall)?

    Three things I'd be looking at in your case...duct leaks, air balance, reduction of infiltration (leaky house). You are bound to see an improvement by addressing all three of these concerns. Having a Manual J heat load calculation done for your house so from that a cfm requirement per room can be obtained for air balancing would also be a good approach.

    Regardless, the overall problem is that you are not getting enough conditioned air to the master bedroom to replace heat that is lost in winter, or to offset heat gain in summer. In the process of resolving this, the best approach, again, is to address leakage along with air balance.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  5. #5
    Join Date
    Sep 2004
    Location
    Round Rock, TX
    Posts
    25
    Quote Originally Posted by dash View Post
    Posting model numbers would help.
    Hello, thanks. Model info follows:

    HVAC Equipment

    Upstairs
    Furnace 58CVA070---10112 66,000 Btuh Input Capacity
    Evaporator Coil CK3BXA024017AAAA
    Condenser 38EZG024---301-- 2 Ton
    38EZG024300
    Filter EACA (not sure of model, 120v though)
    Thermostat Carrier Thermidistat

    Downstairs
    Furnace 58CVA070---10112 66,000 Btuh Input Capacity
    Evaporator Coil CK3BXA036017AAAA
    Condenser 38EZG036---311-- 3 Ton
    38EZG036310
    Filter EACA (not sure of model, 120v though)
    Thermostat Carrier Thermidistat

  6. #6
    Join Date
    Sep 2004
    Location
    Round Rock, TX
    Posts
    25
    Quote Originally Posted by 4l530 View Post
    >How many supply registers in this room, and what size pipe to each?
    >Manual (or even automatic) volume dampers present at the take-offs from the duct?
    >Length from furnace, and length of run-outs to these registers in the room?
    Flex or metal pipe? Extreme bends?

    If you could some pictures of the ductwork and the run-out(s) that supply that room, it might be helpful.
    Pictures attached.
    1) Hallway outside of Master Bedroom
    2) Master Bedroom (master bath door visible) (Note ceiling fan visible in all photos for orientation purposes)
    3) Return (and input #1)
    4) Input #1 and #2
    Attached Images Attached Images     
    Last edited by mettius; 04-07-2007 at 01:16 PM.

  7. #7
    Join Date
    Sep 2004
    Location
    Round Rock, TX
    Posts
    25

    More Pictures, (From the Attic)

    Here are more pictures, this time from the attic.

    1) Return Branches
    2) Alt. View Return Branches
    3) Alt. Alt. View Return Branches
    4) Hallway Return Box
    5) Conditioned Air Ducts 5 of 'em (all appear to be of equal diameter)
    Attached Images Attached Images      
    Last edited by mettius; 04-07-2007 at 01:32 PM.

  8. #8
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,086
    More thoughts since seeing your pics:

    • Any other rooms have temperature imbalance problems, such as other bedrooms, etc? Particularly in comparison to the master, are any other rooms too warm in winter or too cool in summer?

    • Supply registers in master appear to be stamped steel six way registers with dampers. I don't know why round ceiling diffusers aren't used more in residential ceiling supplies...appearance objections, I suppose. As it is the stamped steel grills are considerably more restrictive than a curved blade register. Also, with room of that size and height of ceiling I'd like to see the air moving out along the ceiling in all directions and then dropping down vs. those existing registers that tend to throw the air more down than out. You want to get as much air in the room moving and mixed as possible to minimize a temperature gradient between floor and ceiling. The adjustable curved blade register is better suited for moving air for this purpose.

    • Are the dampers in each of these registers fully open?

    • Was the master bedroom too cold or hot prior to you having additional returns added? Has the addition of a return in the master made it worse? With the largest return immediately outside the master bedroom door, plus the one in the room itself, it is possible too much return is occurring for the amount of supply going into the room. Kind of rare...most time residential returns for bedrooms are not enough.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  9. #9
    Join Date
    Sep 2004
    Location
    Round Rock, TX
    Posts
    25
    Additional Reterns:
    This was new construction, so the additional returns were added to modify the default design, supposedly everything was rebalanced by the HVAC contractor.
    So, I've only ever experienced it like this.

    Other Rooms:
    I've not noticed a perceptible difference (except for the Utility room with the door closed (no return there) in the other rooms vs. the main open areas of the house. Note: The master bathroom and closet (which is located off of the master bath (you walk into master bath, then have two doors one to the toilet room, and the other to the walk in closet) is always warmer than is the master bedroom (again, no returns in the bathroom/closet)

    I'll go check the dampers... Yup fully open. BTW, the little fins on it actually send air out in four directions (each quadrant is oriented a different way, dunno if that is of any consequence).

  10. #10
    Join Date
    Sep 2004
    Location
    Round Rock, TX
    Posts
    25
    I don't know why I didn't think of this before...
    Ever since we moved in we sometimes notice a "fresh" smell in this room.
    I don't know how to really describe it, of any rhyme or reason as to why, but this room definitely seems to feature a different oder sometimes.

    When I finished (polyurethane) some woodworking furnature in one of the spare bedrooms, I think I noticed the oder seemed to collect in the master bedroom as well. I don' know if it is related...

  11. #11
    Join Date
    Feb 2004
    Posts
    2,597
    What kind of wine is that in pic #2?

  12. #12
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,086
    Quote Originally Posted by mettius View Post
    I don't know why I didn't think of this before...
    Ever since we moved in we sometimes notice a "fresh" smell in this room.
    I don't know how to really describe it, of any rhyme or reason as to why, but this room definitely seems to feature a different oder sometimes.

    When I finished (polyurethane) some woodworking furnature in one of the spare bedrooms, I think I noticed the oder seemed to collect in the master bedroom as well. I don' know if it is related...
    The "fresh" smell in the master bedroom very well could be air from outdoors being sucked into the house because the bedroom has too much return compared to supply. Have you noticed overall your house air becoming dry in winter? That's a sure sign you're pulling in too much outside air through cracks, gaps, etc, in the outer walls.

    The polyurethane smell likely spread to others rooms when the blower ran.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  13. #13
    Join Date
    May 2006
    Location
    east central indiana
    Posts
    1,117

    Cool

    Originally posted by mettius
    Master Bedroom is always 5 degrees colder than rest of house. We've only been here two years, but it seems to hold true in both heating and cooling season.
    Just to clarify. Do you actually mean the Master Bedroom is 5* colder in the winter and in the summer?
    Or is it 5* colder in winter, and 5* warmer in summer?
    This space for rent.

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