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  1. #1
    Join Date
    Apr 2007
    Location
    Canton, MI
    Posts
    7

    Air Cond temp difference

    For some background, when I moved into my current home about 7 years ago, I've had to have the A/C charged every year for the first four years until someone finally found a leak. It was at the king valve outside the house. I was told that if the valve was heated too much when it was installed it could have been damaged. The tech sealed the caps on the king valve and the charge lasted until now, about three years. It got warm here in Michigan a few weeks back and the house got warm so I figured, I'd try to fire it up. I'm always scared that I'll have another problem so I start it as early as I can to prepare myself for the recharge bill that may be coming. It was 81 degrees in the shade outside and the temp coming out of my vents was 62 degrees. The house was at 75 and I wanted to cool it to 72. I let the system run for about a 1/2 hour and it only brought it down one degree. Am I looking at another recharge or do these numbers seem OK and I'm just getting more and more paranoid each year? The house is 11 years old, two story and 2200 sqft with alot of windows.

    Thanks!

    Brian

  2. #2
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,376
    You have to measure temp difference over the coil. Measure air going into the furnace and then out of the furnace maybe in the main supply duct. Should be 15-20° diff. Dropping 1° in 1/2 hour doesn't sound out of line.

  3. #3
    Join Date
    May 2004
    Location
    Los Angeles, CA
    Posts
    1,560
    Dear Bchetrick

    First, and foremost let me welcome you to our forum. Second of all, I’m sure you’re only repeating what the service technician called it, but you more than likely do not have a “king valve”. A king valve is the outlet isolation, and sometimes access valve, that is found directly downstream of a liquid line receiver, usually found only in an older commercial refrigeration system. You more than likely are referring to the suction (larger copper insulated tubing entering the condensing unit) isolation/access valve, or the liquid (smaller un-insulated copper tubing leaving the condensing unit) isolation/access valve.

    Based on the information you posted the last service technician either terminated the leak completely, or at least reduced the leakage rate with his, or her, repairs (last three years operating satisfactory).

    Either this same area is still leaking, another area or areas are leaking, or the system is charged correctly, and no measurable leaks are present at this time, but without a professional completing a comprehensive diagnostic operational run test on your system, it would be impossible for anyone here at this thread, or at this forum in fact, to accurately determine if your system is operating correctly, and with the correct refrigerant charge.

    With the extremely limited operational temperatures and time you have already posted, like BaldLoonie has already posted, they don’t seem “out of line”. My suggestion would be for you to let the system operate for a longer period of time, measure both the return and supply air, as BaldLoonie has posted, check for any ice that may be forming at the condensing unit outside, or at the evaporative coil assembly inside, and then if no ice is found, and the system can cool the house down, then you jusy might be good to go.

    On the other hand, if you see any ice anywhere on your system, and your air filter is clean, or the system cannot cool the house down, then it just might be time to call in a professional.

    Hope this helps…………

    Respectfully Submitted,
    John J. Dalton CM

  4. #4
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,750
    Some Carriers from that era did have king valves.
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  5. #5
    Join Date
    Apr 2007
    Location
    Canton, MI
    Posts
    7
    Thanks for the response guys....

    When we get warm again, I'll let it run longer and see what happens. As for the "king valve" the tech told me that this is the point where the connection is made to the lines from the unit in the house. From what I understood, the outside compressor unit is pre-charged with refrigerant and the lines coming out of the compressor unit terminate at this "king valve." When the pipes from the inside unit are sweated to this valve is when I think he meant the valve could get damaged.

    I change the filter every three months, which brings up another question. I was told by one of the techs that recharged the system that these washable, reuseable filters are very restrictive and not to use them. He recommended using the old fiberglass type. I just can't get myself to buy a 2.00 filter. I have this idea that if I can see through it, it can't be getting all the dirt. So, I use one of these corrugated paper filters and threw out the reuseable one. Do you have any opinions on the different types of filters out there?

    Thanks,

    Brian

  6. #6
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,086
    Pleated filters are better than fiberglass. A two inch thick pleat is better than a one inch thick pleat, and will take a little longer to load up with dirt, due to more surface area.

    The "hog's hair" type washable filters are worthless.

    Proper name for nit picky purposes for the valve in question is "base valve" or "suction or liquid service valve", unless it really is a king valve.
    • 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.

  7. #7
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    16,995
    Quote Originally Posted by bchetrick View Post
    Thanks for the response guys....

    When we get warm again, I'll let it run longer and see what happens. As for the "king valve" the tech told me that this is the point where the connection is made to the lines from the unit in the house. From what I understood, the outside compressor unit is pre-charged with refrigerant and the lines coming out of the compressor unit terminate at this "king valve." When the pipes from the inside unit are sweated to this valve is when I think he meant the valve could get damaged.

    I change the filter every three months, which brings up another question. I was told by one of the techs that recharged the system that these washable, reuseable filters are very restrictive and not to use them. He recommended using the old fiberglass type. I just can't get myself to buy a 2.00 filter. I have this idea that if I can see through it, it can't be getting all the dirt. So, I use one of these corrugated paper filters and threw out the reuseable one. Do you have any opinions on the different types of filters out there?

    Thanks,

    Brian
    Generally, the more expensive the filter (comparing similar sizes) the more particulate matter it will catch. Not every filter can be used with every system. It has to be able to pass enough air for the system to work properly.

    Your system paperwork should give you the filter options.
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  8. #8
    Join Date
    Apr 2007
    Location
    Canton, MI
    Posts
    7
    It's me again....

    I started up the A/C the other day, it was 82 outside and 76 inside. I turned it on in the late afternoon and I don't know if it ever shut off but I put my foot over the register a few hours later and didn't feel any air coming out. I looked outside at the compressor and the lines coming into the side of the unit had a block of white frosty ice all over it. I went to the basement and saw that the insulated line coming out of the unit was frozen over as well.

    I just turned it on again a few minutes and right now it is 88 outside, 76 inside and the temp coming out of the register is 65.4.

    I'm going to have the HVAC guy come and take a look but can anyone tell me why it froze up? Is that an indication of being low on R22? Any ideas? I would like to have an idea of what is happening so I can follow the conversation I'll be having with the technician.

    Thanks,

    Brian

  9. #9
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,086
    Changed your filter recently?
    • 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.

  10. #10
    Join Date
    Apr 2007
    Posts
    6,285
    Could be your inside fan not coming on or low on charge. Or outside unit staying on all thew time....even when its not suppose to....filter....outside fan motor not working...clogged coil....

  11. #11
    Join Date
    Apr 2007
    Location
    Canton, MI
    Posts
    7
    Definitely not the filter. I replace it every three months religiously. I even write the date on it when I replace it.

    Both fans are running now.

    Brian

  12. #12
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,086
    All supply vent dampers open?

    All return grills unobstructed?
    • 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
    Apr 2007
    Location
    Canton, MI
    Posts
    7
    the only dampers closed are the ones for the basement ducts. all return registers are high on the walls and unobstructed...

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