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  1. #1
    Join Date
    Apr 2005
    Posts
    83
    I have a 2 stage heat pump with AC Traine unit. Yesterday here in Orlando we had a 92-degree day and I noticed my house was not cooling as well as usual. Mind you we were doing a lot of housework and having the carpets cleaned.


    My question: What should be the temperature coming out of my ceiling registers if I have the AC set to 70 and it's a very hot, sunny, humid 90 degrees outside?

    I was getting between 64.5- 65.5.

    Thanks,

    Felix

  2. #2
    Join Date
    Jun 2003
    Location
    Hell Hole Swamp
    Posts
    4,180
    Lots of variables affect the supply air temperature, the thermostat setting is not one of them, what was the air temp at the return?

  3. #3
    Join Date
    Nov 2002
    Location
    VA
    Posts
    296

    More Data Please and Thank you...

    Need more data: What is the temperature of the air going in to and coming out of the evaporator (indoor coil)? What is the indoor dry bulb and wet bulb temperature? What is the outdoor ambient temperature? What is the temperature of the air coming out of the condenser (outdoor coil)? What is the temperature of the Suction Line going into the compressor? What is the temperature of the Liquid Line coming out of the compressor? What is the temperature of the Liquid Line going into the Evaporator (delta loss from compressor to evaporator)? What is the Liquid Line Pressure coming out of the compressor? What is the Suction Line Pressure going into the compressor? What refrigerant does your system use?

    Given the above parameters a skilled HVAC tech can give you an authoritative professional answer. Note: This assumes the tech is familiar with your particular equipment vendor’s product. Various manufactures deploy deferent solutions to the refrigeration cycle to differentiate themselves in the market place. I am continuously awed at the innovation that goes into today’s residential equipment. The balance between cost and function is a dynamic that is in constant motion.

    Now you understand why there is a fee involved in giving you an estimate for service. When you call your physician do you expect him to diagnosis over the phone? Of course not, therefore please have patience with the replies on this forum if they ask you for more information. While many naïve homeowners believe that there are obviously easy answers to their questions, they are not aware of the complexities of the equation. Hope this helps...

  4. #4
    Join Date
    Apr 2005
    Posts
    83

    Re: More Data Please and Thank you...

    Originally posted by faith
    Need more data: What is the temperature of the air going in to and coming out of the evaporator (indoor coil)? What is the indoor dry bulb and wet bulb temperature? What is the outdoor ambient temperature? What is the temperature of the air coming out of the condenser (outdoor coil)? What is the temperature of the Suction Line going into the compressor? What is the temperature of the Liquid Line coming out of the compressor? What is the temperature of the Liquid Line going into the Evaporator (delta loss from compressor to evaporator)? What is the Liquid Line Pressure coming out of the compressor? What is the Suction Line Pressure going into the compressor? What refrigerant does your system use?

    Given the above parameters a skilled HVAC tech can give you an authoritative professional answer. Note: This assumes the tech is familiar with your particular equipment vendor’s product. Various manufactures deploy deferent solutions to the refrigeration cycle to differentiate themselves in the market place. I am continuously awed at the innovation that goes into today’s residential equipment. The balance between cost and function is a dynamic that is in constant motion.

    Now you understand why there is a fee involved in giving you an estimate for service. When you call your physician do you expect him to diagnosis over the phone? Of course not, therefore please have patience with the replies on this forum if they ask you for more information. While many naïve homeowners believe that there are obviously easy answers to their questions, they are not aware of the complexities of the equation. Hope this helps...
    Holy crap! I'm not trying to be naive, just trying to determine if I need to get an HVAC mechanic in! No reason to call an HVAC mechanic in if nothings wrong, correct? Or should I just throw money away because some people are just to good or to valuable to answer a question.

    Felix

  5. #5
    Join Date
    Apr 2005
    Posts
    83
    Originally posted by swampfox
    Lots of variables affect the supply air temperature, the thermostat setting is not one of them, what was the air temp at the return?
    Swampfox, to answer your question the return had a temp of around 79 degrees due to the rug steamer running and the dryer running with the door open to the laundry room which is around 5 feet away.


    Thanks,
    Felix

    [Edited by nyrfan on 05-16-2005 at 09:17 AM]

  6. #6
    Join Date
    Apr 2005
    Posts
    83
    dup post sorry

    [Edited by nyrfan on 05-16-2005 at 09:18 AM]

  7. #7
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,346
    Originally posted by nyrfan
    [BSwampfox, to answer your question the return had a temp of around 79 degrees due to the rug steamer running and the dryer running with the door open to the laundry room which is around 5 feet away.

    [/B]

    There's your answer, most likely. In addition to the high latent heat load from a humid day outdoors, you were adding moisture to the air by running a rug steamer and sensible heat via the dryer (though the dryer does not add a great deal of heat to the house unless for some odd reason it is venting to the house rather than outdoors).

    An air conditioner works much harder to remove moisture from the air than it does sensible temperature. To remove moisture from the air, the cooling coil must first pull enough heat from the moisture in the air to cause it to condense on the coil, where the condensed moisture then drains off and out of your house. This heat that must be removed to cause water vapor to condense into liquid water is called latent heat of condensation. It is a heat load your a/c system sees as well as the more familiar air temperature heat load most of us are familiar with.

    Once you've put your carpet steamer away, the carpets have dried, and your housekeeping activities have ceased for a time, you will likely find your a/c system's operation returning to normal due to a lower amount of moisture being added to the air from these activities.
    • 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.

  8. #8
    Join Date
    Apr 2005
    Posts
    83
    Thank you shophound! I had a feeling it had to do with the steamer because it seemed to have started this weekend when we stated to clean the rugs (Then again I got concerned as this was our 1st day over 90 this year with lots of humidity). I just wanted to be sure this might be the case as I have a dog at home that loves the cold (spoiled dog!)and if there might be a probelm I would want to get someone in there ASAP. I will monitor it over the next day or two and see if it get back to normal.

    Thanks again,
    Felix

    [Edited by nyrfan on 05-16-2005 at 10:16 AM]

  9. #9
    Join Date
    Sep 2004
    Posts
    172
    nyfran once the extra humidity from the carpet cleaning activities is over you can do a couple of simple tests that can determine if you might have a problem. Take a outside ambient air temp and try to do this test when the outside air is between 80f and 85f degrees. Check humidity levels inside the house try to do this test when the humidity is between 45% and 55% also need between 70f and 75f interior house temp. Now go to your thermostat and crank it down to around 60 so the 2nd stage kicks in for max cooling go to the return air opening, check the filter to be sure it is clean and take a good temperature reading at the face of the return grille, then go to the supply outlet that is close to the unit and take a temp reading. Under the above noted conditions you should have a temperature differential of approx. 20f degrees if it varies by more than 5f degrees one way or the other I would have a tech in to evaluate the system. As noted above systems are very different the general rule of thumb may not apply to your particular setup. I would probably have a tech look at it anyway word on the street is that 75% of residential units are either undercharged or overcharged the installers rarely check and adjust charge level to compenstae for duct work static/ flow across coils etc. all affect proper charge level. Ask your tech for a checklist of values taken for your unit there should be a baseline taken before adjustment and a sheet filled out for after any adjustments (if needed) are done, this sheet should list system pressures/temps/airflow/amp readings etc. A lot of techs skip this part LOL I like the ones that chew backer spit a bit and then say awh shes fixed up, you owe 150 bucks! will that be cash/check or credit card.
    When you give a lesson in meanness to a critter or a person, don't be surprised if they learn their lesson.

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