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  1. #1
    Join Date
    Apr 2005
    Posts
    83
    This is my 1st July here in Orlando and have a question about my AC unit. It痴 a Traine Multi Stage Heat Pump. Never had cental air befor only window units living in NY.

    1st let me say I had the unit serviced a month ago and all came back ok so this is just for my sanity.

    Is this normal for a FL House with central air (I知 guessing so but what to be sure):

    House is 1700 sq ft cathedral ceilings, 8 ft on the low end 12 ft or so in the middle. House is 60 ft long and 40 ft wide.
    Sun beats on the roof all afternoon (Not the morning), no shade at all, attic is like 140 degrees (Guessing not actual)!
    Ductwork runs trough attic.
    55% humidity or so at all time in the house.
    78 degrees at the return, 62 degrees at the ceiling vents (I知 guessing there is some heating from tracking through the attic as I understand normal is closer to 20 degrees)).

    So here is my question, I値l use Friday as an example.
    92 degrees outside, with about 55% humidity, no clouds at all sun beating on my roof, heat index of 104. House stayed at the set temperature of 76 all morning until about 2PM when the temperature began to rise to about 78 and never came down again until about 8PM. My unit ran the whole time never shutting off till about 8pm. Is this normal or could there be a problem? I知 guessing it痴 normal due the Sun and excessive heat but just want to be sure.

    TIA,
    Felix

  2. #2
    Join Date
    May 2003
    Location
    Sarasota. Fl
    Posts
    1,240
    My house does the same thing during June, July and August.

    My problem is old leaky windows. But Im not willing too part with 6 K to change them just yet.

    Your problem is most likely something along the same lines...attic insulation....windows ...etc.

    That is assuming that your maintenance was done right and your system is delivering full capacity and thats a big assumption.
    It is the job of thinking people not to be on the side of the executioners.

    ~Albert Camus

  3. #3
    Join Date
    Jul 2005
    Posts
    6
    Clean condensor coils add attic venyilator

  4. #4
    Join Date
    Sep 2001
    Location
    Vancouver Canada
    Posts
    996
    Yes it is normal in a lot of cases for a system to rise a couple of degrees during the hottest part of the day. Some shade on the roof would certainly help. Also make sure you have adequate ventilation in the attic. Also if possible check the insulation on the ductwork and make sure that it is well sealed. About all you can do with temperatures in that range. Delta T may be a little low 16 degrees but there is sure to be some heat gain in the attic ductwork, I suggest you try taking the temp. right at the airhandler and see what that is in comparison to at the registers. It will certainly tell you how much heat gain there is in the attic ductwork.
    "Go big or Go Home"

  5. #5
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    92 outside and 78 is the best it wil do inside,design or mormal outdoor temps more like 95 ,somethig is wrong.


    Should be able to maintain 78 or "indoor design" on a 95ー day.

  6. #6
    Join Date
    Apr 2005
    Posts
    83
    Originally posted by Black Adder
    Yes it is normal in a lot of cases for a system to rise a couple of degrees during the hottest part of the day. Some shade on the roof would certainly help. Also make sure you have adequate ventilation in the attic. Also if possible check the insulation on the ductwork and make sure that it is well sealed. About all you can do with temperatures in that range. Delta T may be a little low 16 degrees but there is sure to be some heat gain in the attic ductwork, I suggest you try taking the temp. right at the airhandler and see what that is in comparison to at the registers. It will certainly tell you how much heat gain there is in the attic ductwork.
    Tested the air at the handler, was 55.9, return was 78, closest register was 62.5.

    My themostat registered 137 in the attic yesterday.

    Question: My return is between my from door and the door to the laundry room which leads to my garage, can this be an issue at all?

    I know there is not way to change that, just wondering?

    Felix

    [Edited by nyrfan on 07-12-2005 at 10:30 AM]

  7. #7
    Join Date
    Jan 2005
    Posts
    340
    Originally posted by nyrfan
    Tested the air at the handler, was 55.9, return was 78, closest register was 62.5.

    My themostat registered 137 in the attic yesterday.

    Question: My return is between my from door and the door to the laundry room which leads to my garage, can this be an issue at all?
    You are getting quite a bit of heat gain in the supply duct work. It sounds like you could use some better attic ventilation -- 137 is high for a properly vented attic even here in central Florida. Another option would be to better insulate the ducts.

    OTOH, if you are measuring 78 degrees at the plenum with 78 degree return air, then you don't have any leakage in your return ducts and they must be very well insulated.


  8. #8
    Join Date
    Apr 2005
    Posts
    83
    Originally posted by travisfl
    Originally posted by nyrfan
    Tested the air at the handler, was 55.9, return was 78, closest register was 62.5.

    My themostat registered 137 in the attic yesterday.

    Question: My return is between my from door and the door to the laundry room which leads to my garage, can this be an issue at all?
    You are getting quite a bit of heat gain in the supply duct work. It sounds like you could use some better attic ventilation -- 137 is high for a properly vented attic even here in central Florida. Another option would be to better insulate the ducts.

    OTOH, if you are measuring 78 degrees at the plenum with 78 degree return air, then you don't have any leakage in your return ducts and they must be very well insulated.

    I actually meant to say 113, not 137. Would that be considered high still with 6 hours of directly sunlight? I have 4 roof vents on the west side of the house each measure appox. 5ft long by 2 ft wide (going by sight). Should I have more? House is 60 x 40.

    Also I'm a bit confused by your 2nd comment. I only measured 78 at the return, that is the other 78 you are mentioning?

    [Edited by nyrfan on 07-12-2005 at 10:52 AM]

  9. #9
    Join Date
    Jan 2005
    Posts
    340
    Originally posted by nyrfan
    I actually meant to say 113, not 137. Would that be considered high still with 6 hours of directly sunlight? I have 4 roof vents on the west side of the house each measure appox. 5ft long by 2 ft wide (going by sight). Should I have more? House is 60 x 40.
    113 this time of year sounds OK if you have a dark roof, so I think your ventilation is all right. But you are getting more heat gain in your duct work than I would expect - about three degrees for a 25' run of R-6 duct would be more typical in your circumstances.
    Originally posted by nyrfan
    Also I'm a bit confused by your 2nd comment. I only measured 78 at the return, that is the other 78 you are mentioning?
    Because I thought you said so, but maybe I misunderstood what you meant <grin>.
    Originally posted by nyrfan
    Tested the air at the handler, was 55.9, return was 78, closest register was 62.5.
    If you didn't measure the temperature at the return plenum, then let's look at that just to see how much heat gain is in the return.

  10. #10
    Join Date
    Apr 2005
    Posts
    83
    Originally posted by travisfl
    Originally posted by nyrfan
    I actually meant to say 113, not 137. Would that be considered high still with 6 hours of directly sunlight? I have 4 roof vents on the west side of the house each measure appox. 5ft long by 2 ft wide (going by sight). Should I have more? House is 60 x 40.
    113 this time of year sounds OK if you have a dark roof, so I think your ventilation is all right. But you are getting more heat gain in your duct work than I would expect - about three degrees for a 25' run of R-6 duct would be more typical in your circumstances.
    Originally posted by nyrfan
    Also I'm a bit confused by your 2nd comment. I only measured 78 at the return, that is the other 78 you are mentioning?
    Because I thought you said so, but maybe I misunderstood what you meant <grin>.
    Originally posted by nyrfan
    Tested the air at the handler, was 55.9, return was 78, closest register was 62.5.
    If you didn't measure the temperature at the return plenum, then let's look at that just to see how much heat gain is in the return.
    OK so let me be sure we are on the same page:
    Return = Where the air gets sucked into the unit (78)
    Air Handler: Unit inside my garage (Where I change the air filter (55.9). BTW: I tested this by sticking a thermostat into the unit where the serviceman put his in.
    Register: Ceiling duct providing the air: 62.5

    Now if that's correct can I just assume it's the high heat and lack of attic insulation and?

    Thank you "VERY MUCH" for all of your help.

    Felix

  11. #11
    Join Date
    Jan 2005
    Posts
    340
    [QUOTE]Originally posted by nyrfan
    OK so let me be sure we are on the same page:
    Return = Where the air gets sucked into the unit (78)
    Air Handler: Unit inside my garage (Where I change the air filter (55.9). BTW: I tested this by sticking a thermostat into the unit where the serviceman put his in.
    Register: Ceiling duct providing the air: 62.5

    Now if that's correct can I just assume it's the high heat and lack of attic insulation and?
    The return register is the grille where the air gets sucked into the return duct work, which is routed through your attic and connects to the return plenum (the metal or duct board box connected to your air handler / furnace) in the garage. The supply plenum is connected to the air handler / furnace and thence to the supply duct work, and the supply registers.

    You have a 6.6 degree drop in your supply duct work. If you measure at the return plenum we can see how much heat gain we have in the return duct work. The heat gain can be caused by poor insulation or even leaks in the ducting.

  12. #12
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Since you are already getting 78 to 55.9 temp. drop,I doubt you'll see much Gain in the return.

    Didn't you say ,the return was ,Just thru the adjacent wall?

  13. #13
    Join Date
    Apr 2005
    Posts
    83
    [QUOTE]Originally posted by travisfl
    Originally posted by nyrfan
    OK so let me be sure we are on the same page:
    Return = Where the air gets sucked into the unit (78)
    Air Handler: Unit inside my garage (Where I change the air filter (55.9). BTW: I tested this by sticking a thermostat into the unit where the serviceman put his in.
    Register: Ceiling duct providing the air: 62.5

    Now if that's correct can I just assume it's the high heat and lack of attic insulation and?
    The return register is the grille where the air gets sucked into the return duct work, which is routed through your attic and connects to the return plenum (the metal or duct board box connected to your air handler / furnace) in the garage. The supply plenum is connected to the air handler / furnace and thence to the supply duct work, and the supply registers.

    You have a 6.6 degree drop in your supply duct work. If you measure at the return plenum we can see how much heat gain we have in the return duct work. The heat gain can be caused by poor insulation or even leaks in the ducting.
    My return vent is actually near to the floor; the air that is getting sucked immediately passes through the filter and into the air handler into the garage and up into the attic to the ductwork. I知 sorry if I知 confusing matter but I知 trying to understand it the best I can and find it very interesting.

    Hallway contains register vent near floor.
    Garage (Direct opposite of hallway) contains handler, which goes up to attic.
    Attic (Above air handler) breaks off into ductwork

    Now the 55.9 I measured was between the air handler the the garage ceiling, is that the supply plenum?

    Hope that makes sense..

    Felix

    [Edited by nyrfan on 07-12-2005 at 12:27 PM]

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