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  1. #1
    Join Date
    Jun 2005
    Posts
    11
    I know, there are variables, but approximately what should be the difference in temperature between return air and register air? I have a brand new system and it is running almost constantly on hot days. The installer came back and checked the charge but that was in late January at it was barely 70 degrees outside. Should I insist they come back again? My difference in temp from return to register is 15 degrees. I measured the register air at a register halfway down the trunk line in order to get the average when taking heat gain from the attic into account. Thanks in advance.


  2. #2
    Join Date
    Jun 2005
    Posts
    178

    temp difference

    the temp diff sounds right it is usally about 10 to 15 degrees difference.it sounds to me like you have a problem with your insulation or something letting your air escape or allowing the heat get in and also where is your thermostat located. it should be in a central spot or close to the return air to get atrue reading and make sure its not in a spot where the sun is on it.also do you have a return at the highest point in the house that would make a difference.

  3. #3
    Join Date
    Jun 2005
    Posts
    11
    Thanks for the reply coolcray, I actually have two ceiling returns, one is directly above the thermostat. My house very old and I'm in the process of restoring it. Currently the only insulation is in the attic. I know more insulation will help, but the heat worked very well. If the problem is purely the lack of insulation I'll just have to grin and bear the utility bill unitl I get around to adding more. I have added an attic fan to help reduce heat transfer to the ductwork. Someone in another forum suggested addin additional insulation to the ducts. My main concern is that if something is wrong with the unit I want to get it right before too much time passes. I'm just about to the point of hanging blankets over the windows when I think of the electric meter spinning away!

  4. #4
    Join Date
    Jun 2005
    Posts
    178

    air temp

    if all the ducts are insulated with duct wrap and the house is old thats all you can do the heat from out side is radiating right through the walls and any air gaps it can get through. the unit is right on with the temp of the air. sometimes the attic fan will cause a air pull through the house and pull the heat in as well as venting the attic space. you want to make sure your attic is sealed from the house and not pulling out the ac and pulling in the heat at the same time

  5. #5
    Join Date
    Feb 2003
    Location
    Huntsville,AL
    Posts
    4,125
    white blinds, reflective film &solar screening will prevent considerable heat gain -- awnings will even more.

    insulation in attic will decrease energy needs both for cooling & heating.

  6. #6
    Join Date
    Jun 2005
    Posts
    11
    Thanks again coolcray. I guess I'll get some cans of spray foam and go to work plugging any gaps in the attic. I have two windows up there open, but I guess there could still be some air pulling through around ceiling fixtures and stuff.

  7. #7
    Join Date
    Jun 2005
    Posts
    11
    Cem, I have white plantation blinds on most of the windows, but there is one room with BIG windows that don't have blinds yet. I might have to improvise something to cover those windows with for the time being. Thanks for the input.

  8. #8
    Join Date
    Jun 2005
    Posts
    178

    air temp

    if you have open windows up there that should be plenty of intake air for the fan to pull from. i think i would consentrate on making sure that your attic opening to the house is sealed and try some window coverings that will deflect the sun and heat

  9. #9
    Join Date
    Jun 2005
    Posts
    11
    Thanks to both of you for being so helpful with my first participation in this forum!

  10. #10
    Join Date
    Jul 2001
    Location
    Gold Coast of Connecticut
    Posts
    4,543
    A properly sized cooling system will run 100% of the time at design temperature. Has it been hot?
    Aire Serv of SW Connecticut- Gas heat, dual fuel and central a/c systems installed and serviced

  11. #11
    Join Date
    Apr 2004
    Location
    Niantic, Illinois
    Posts
    545
    look at the hole in the wall where the thermostat wires come out behind the stat. Is the hole sealed, filled with caulk or something? If not it should be, hot air can be cruising through your wall like an chimney and right into your thermostat.

  12. #12
    Join Date
    Jun 2005
    Posts
    11
    The high temperature has approached 95 for the last week, unusually hot for the area. I plugged up th ehole behind the thermostat when I changed it to a programable one (which cut the natural gas bill in half)

  13. #13
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    5,989

    Exclamation Delta T

    Originally posted by coolcray3
    the temp diff sounds right it is usally about 10 to 15 degrees difference.
    TEMPERATURE DIFFERENCE as stated SHOULD BE > 17'F.
    For Example,
    77'F Room Temperature
    60'F Diffuser

    That should provide R.H. of << 58%.

    AND that's just for an average system without Variable Speed air handler.

    Did you try Medium air flow setting on air handler instead of High?
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

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