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  1. #14
    Join Date
    Jul 2005
    Posts
    40
    Demand that it be fixed even if it meant to install a newer system to maintain that temp? Assuming that it is undersized.

    To me 75 isn't liveable. But it will do. I'll set the thermostat at 75 tomorrow and see what happens. I know it won't go above 93 outside. And I know it will go above 75 inside.

    So if my unit is just the right size. It won't go lower than 75 on a 93 degree day?

    And if it was oversized that is how I maintained my 68 degree conditions?

    Thanks for the valuable info.



  2. #15
    Join Date
    Mar 2002
    Location
    Concord, CA
    Posts
    2,633
    We can't assume that it's undersized yet. There's still every chance in the world that there's something to be fixed. But if not... IF the system is working perfectly and can't maintain 75 degrees inside on a 93 degree or less day then yes, you have every right to an upgraded system in my opinion. Yeah... like that will hold up in court. (Your honor: Some online guy said so!) :^)

    "So if my unit is just the right size. It won't go lower than 75 on a 93 degree day?"
    Yep. At least that would be the case for Springfield according to HVAC-Calc.

    "And if it was oversized that is how I maintained my 68 degree conditions?"
    If you maintained 68 before on hot days, yes. Even an undersized unit could get to 68 if it's not hot. But if it was maintaining 68 at design conditions then that's definitely an oversized unit. Well... oversized according to the social architects that live in ivory towers. Obviously some of us would disagree.

  3. #16
    Join Date
    Jul 2005
    Posts
    40
    ok. just a few more questions, then I'll leave you alone.

    This is what I'm going to request, because after all, I'm still sweating and it is MY electric bill:

    Make the landlord make the techie:

    1. Find out the CFM x TD x 1.08

    2. Find out why the closest supply vent isn't producing any air. (as this is the hottest room in the Apt)

    3. Check the ducts for leaks.

    4. If then all is fine find out why the A/C still can't maintain design conditions.


    Now the questions:

    1. Is this reasonable?
    2. What does the equation CFM x TD x 1.08 add up to?
    3. Why am I not getting any air from that one vent?
    4. If an undersized unit can still produce cold air during the day (just not enough of it) then why is my supply air warm during the day?
    5. Should all vents blow the same amount of air at the same temperature. Or is it normal for all of them to have different temps at different air force?
    5. Why are P-Traps installed in A/C drains?
    7. If the system was low on R-22 wouldn't it freeze up?


    Again thank you so much for your time.




    [Edited by ablib on 07-04-2005 at 06:09 AM]

  4. #17
    Join Date
    Mar 2002
    Location
    Concord, CA
    Posts
    2,633
    1) Is what reasonable? Finding out the delivered capacity? IF they insist that nothing is wrong but it still can't maintain 75 inside when it's 93 or below outside then yes it's reasonable. But that doesn't mean that the tech is equipped or even knows how to do so. And even if he is and can, that doesn’t mean that the owner will want to pay for it. Plus, if the tech comes up with other "fix the box stuff" then you of course have to be reasonable and let that play out. And I almost certainly expect that the tech will want to do more troubleshooting of his own before he’ll entertain any of the stuff we’re talking about. So expect that and let it happen.
    2) The equation adds up to sensible capacity. Sensible capacity is that which you sense. It's temperature reduction. Latent capacity is humidity removal, which is determined with a different formula. Since you’ve focused primarily on the actual temperature and haven’t mentioned humidity, I’ve focused on sensible capacity.
    3) Dunno. It's broke?
    4) Dunno. It's broke? :^) Keep in mind that it's all relative. The warmer it is inside and out, the warmer the air that the system will produce. But even so the temp drop should be around 17 to 20 degrees, as you were discussing with the other forum member. So if it's 80 in the house the air coming out should be around 60, give or take. If it's 85 in the house then the air should be around 65, give or take. That's assuming that everything else is kosher.
    5) To keep conditioned air from escaping through the drain. And in some cases to keep water from overflowing the drain pan. (Don't make me explain that one.)
    6) Maybe. Maybe not. There are too many variables to know what would happen exactly.

    FYI: There's checking for duct leaks and then there's checking for duct leaks. Just looking around at the outside of the ducts can sometimes reveal major leaks. But often times there are leaks hidden from view. A Duct Blaster test can reveal those leaks. But that's a pipe dream so forget about it. You'll never get them to pay for such a thing. Just getting them to measure delivered capacity with our formula is tough enough. But at least that would take only a half hour or so if the tech is equipped to do it.

    Somewhere in all this a Manual J heat load calc might be needed. But I'm more in favor measuring output. A Manual J can be fudged to deliver any result. They could do the calc and have it say that the unit is big enough and that you need to clam up. But if they measure the output and it is actually delivering two tons and if it can't maintain 75 inside when it's 93 outside then that's irrefutable evidence that it is undersized. Though we still have the niggling little issue of your downstairs neighbor's heat rising to your space.

  5. #18
    Join Date
    Aug 2003
    Location
    Central Kentucky
    Posts
    6,247
    Originally posted by Irascible
    Just getting them to measure delivered capacity with our formula is tough enough. But at least that would take only a half hour or so if the tech is equipped to do it.
    Wouldn't you love to see the look on the contractors face when he is asked for this.

    Have you set up a Google alert for Carbon Monoxide yet?
    Click here to find out how.

  6. #19
    Join Date
    Jul 2004
    Posts
    47
    Originally posted by ablib
    Demand that it be fixed even if it meant to install a newer system to maintain that temp? Assuming that it is undersized.

    To me 75 isn't liveable. But it will do. I'll set the thermostat at 75 tomorrow and see what happens. I know it won't go above 93 outside. And I know it will go above 75 inside.

    So if my unit is just the right size. It won't go lower than 75 on a 93 degree day?

    And if it was oversized that is how I maintained my 68 degree conditions?

    Thanks for the valuable info.


    ROFL! 75 isnt livable! Thats too funny. I would love to have my house at 75 in the summer time here in lame ass california. If u want to pay 600 a month for electric u can.
    Its absoultely retarded the amount of money we pay for electrcitiy here. I cant wait to move to washington/oregon.

  7. #20
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,086
    All right. I can only imagine what I'd find if I were to work on this guy's apartment system. All this discussion about CFM's and such and nobody yet has mentioned that there's a 99% likelihood this Goodman system uses a piston metering device and it is OVERCHARGED. Not grossly overcharged, just enough to drive the occupant batty.

    Fixed orifice systems are critical charge, period. And yet the HVAC industry is full of attic monkeys who couldn't define superheat or subcooling or know how to apply those two VERY useful tools if their life depended on it.

    I also live in an apartment. It's a piston system. It's downstairs so I don't have any attic heat load. The system was cooling but not like I know it could. I didn't even notify the landlord. I took my gauges and Fieldpiece and recovery bottle out to the condenser and pulled out just a smidgen of gas. Checked superheat, subcool, delta T...the system now rocks and keeps humidity at times below 50%. The condenser was replaced before I rented the apartment and I know the in-house staff must've done it, and just gassed it until "pressures looked good". That's the "checking the box" mentality that Irascible referred to.

    Your a/c guy may have checked the system pressures, but if he didn't clamp a thermometer onto the suction line to measure superheat, he missed the boat. You're likely overcharged and your system won't cool worth squat until somebody with competence nails the charge.

    [Edited by shophound on 07-05-2005 at 08:26 AM]
    • 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. #21
    Join Date
    Jul 2005
    Posts
    40
    He did tell me that it was undercharged at 57lb on the low pressure. Don't know the high. He said he filled it to 70-75 on the low and that's where these systems need to be. Keep in mind this was the owner of the outfit.

    He wasn't outside at the compressor long enough to check it, I don't think I just figured he was giving me BS again to make me happy and shut up. He said "you were a little low on freon, I put some in to 70-75 lbs. You should be fine now it's blowing ice cold air."

    Well it wasn't blowing ice cold air. I'm serious this guy was a jerk off.

    What should the charge be on this unit? Could the thermostat be wired for heat pump? If so how do I see if it is. I know at work we had a bunch of thermostats wired for heat pump and when we kicked the air on it would turn the A/C and the heat on at the same time. Just curious.

    [Edited by ablib on 07-05-2005 at 05:38 PM]

  9. #22
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,086
    Bump my 99% up to 100% that you're now OVERCHARGED. This alleged fix-it guy sounds like a prime example of what I call a "manifold jockey"; i.e. someone who slaps a set of gauges onto a system and, no matter what the operating conditions may be, proceeds to charge the system to a preset number in his head that he heard from God knows where.

    You have more than likely given us a prime example at what I was alluding to in my last reply. Prior to this man's intrusion into your system's performance, it was being hampered by an undercharge. Now it's overcharged. You've been either side of the line and you end up with the same result...POOR COOLING PERFORMANCE.

    Where I am right now, it's 95 degrees out and a bit muggy. My apartment's a/c is maintaining 72 degrees and it's cycling. Indoor relative humidity is 52%. It's quite comfy in here. All because I removed about half a pound of refrigerant from the system. That's it! It does NOT take much with a piston orifice system to kill its performance!

    Which, on a closing note, leads me to inform you that if someone with competence could ever get your system performing top notch, you likely would find 68 degrees borderline chilly. Why? Because most people are comfortable at higher temperatures when humidity is lower. With your system being overcharged, it isn't dehumidifying worth squat in addition to the sensible heat removal penalty you're suffering under at the moment.

    Did you sign a lease? If not, I'd bail on this place. The owner and maintenance "help" sound like jerks.
    • 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. #23
    Join Date
    Jul 2005
    Posts
    40
    The "owner of the outfit" was the owner of the A/C contractor that installed the system. I'm thinking he is being resistant because the work is all under warranty.

    By giving the model# of the unit do you know where the numbers should be?

    And what about the heat pump question.

  11. #24
    Join Date
    Nov 2000
    Location
    Upstate, SC
    Posts
    2,914
    Wow...great info guys and patience too, but the one thing that stands out to me from the info given is that all the units in the apartments are the same size. I did apartment work for a while long ago and the one thing that I never saw was all the units the same size. The upstairs unit was almost always larger than the downstairs unit for the reasons already explained. The number of bedrooms made a difference too. We had 1, 2 and 3 bedroom apartments with 1.5, 2.0 and 2.5 ton units respectively. If they were upstairs units, the size was usually increased a half ton. So, if this is a 2 bedroom upstairs apartment, the least it would have had at the places I worked was 2.5 tons and I guarantee you it wouldn't have been oversized...he he. They'd have put smaller if they could have gotten by with it. Anyway, I agree with the others that the unit is most likely undersized and probably not properly charged either. Very few are when you get right down to it. Unfortunately, there might not be a lot the original poster can do about it other than try to get out of the lease and move. It might be worth having a independent contractor take a look at it, but if they choose that path be prepared for a long battle. In the long run, only they can decide if it is worth it. Another thing, ask around and talk to other tenants. How is everyone else's unit doing? It would be interesting to know...

    Bobby

  12. #25
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,086
    Originally posted by ablib
    The "owner of the outfit" was the owner of the A/C contractor that installed the system. I'm thinking he is being resistant because the work is all under warranty.

    By giving the model# of the unit do you know where the numbers should be?

    And what about the heat pump question.
    The model number of the unit tells me it's likely a two ton system. If this apartment was built tightly with good insulation and double pane windows, two tons might be enough capacity. Hmmm...lots of ifs, considering the average construction quality of not only apartments, but just about anything residential built these days.

    If this system is a heat pump, the first thing to look for is if the electric assist heat strips are coming online when there's a call for cooling. Very often a heat pump with electric heat assist will have a separate breaker for the heat strips. If you flip these off and the indoor blower will no longer run, that won't help. But if you flip these breakers off and the cooling performance improves dramatically as the indoor blower continues running, then you're onto something.

    Other heat pump problems require someone who would be willing to be far more investigative than the guy you've had look at the system so far. Check flowrater not seating properly when refrigerant flow is reversed, reversing valve leaking by, a non-biflow liquid line drier installed (which is incorrect), etc.

    You'll know if you have a heat pump if either the thermostat has a functioning "emergency heat" option or when you cycle the unit between heating and cooling, you hear a loud SWOOSH from the outdoor unit.

    But I still lean toward the idea your system is simply overcharged. It's just far too common for this to happen to fixed orifice systems.
    • 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. #26
    Join Date
    Jul 2005
    Posts
    40
    It's a 3 bedroom upstairs apartment. They are all 3 bedroom apartments, 2 levels. 2 ton.

    After talking to the guy next to me in the upstairs, Apt. it seems he is also having this problem.

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