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Thread: evap coil

  1. #1

    Angry

    I have a commercial building 5000 square feet with 18 ft cielings. No insulation just heavy layer black tar on roof.
    Question. What happens to the evaporator if the system is to small to handle the heat load.
    I told the customer he needed two 48,000 btu systems to handle one large area and one 4 ton system to handle the office area.
    I insisted he was going to have problems.
    He was having water filling up in the return air box and complained to me that I installed the system wrong and the systems run constantly. Then he told me that he was going to get someone else to finish the job.
    I told him the water was forming because the Evap's were overloaded
    Was I right or wrong!!

  2. #2
    Join Date
    Sep 2004
    Location
    Memphis
    Posts
    2,502
    I'm not sure why the water is collecting in the return air like that but I dont think its because the unit is undersized. Any moisture should hit the coil & drain right out. Seems to me if the evaporator is too small to handle the building, it'll just run all day & not bring the temp down to the desired setting.
    Life is like a jar of jalapenos. What you do today might burn your ass tomorrow.

  3. #3
    Join Date
    Jul 2006
    Posts
    13

    I'd say wrong

    The having too little tonnage doesn't affect the drain. Have you went back and inspected the system?

  4. #4
    Join Date
    Jul 2006
    Location
    tri state
    Posts
    295
    If the evap too small, delta temp across the coil would be very low.high load.super heat should be very high.with little or no condensation.basic's
    life is at its best when u learn something new.

  5. #5
    What method of sizing equipment did you use for this application.Is the area with 18 ft ceilings a warehouse with a office space in the same building

  6. #6

    High temps

    Temps have been high 99+ 60% humidity and alot of traffic has been in and out of this building. Both systems are belived to be tasked out and as you stated the evaps are to small and they are running constanly. I have checked air flow in the systems and Dt is out of balance untill the building is ready at a certain level adjusting can be perfromed. As of now the customer has told me he was going to get someone else to finish. i will be unable to determine whether the two 4ton air handlers could handle the high heat load of a 5,000 square foot 18 foot high very weak insulated 120 year old brick building. Yes I did use the correct formula and a third system would be needed. I told the customer that we would try and then put another in later.

  7. #7
    Join Date
    Jul 2006
    Location
    Arizona
    Posts
    58
    There are a few problems here.

    If you have a 5000 sq ft building that you are trying to cool, as a rule of thumb you need 20 tons of cooling and more importantly, the building needs heat load calcs to factor ALL of the conditions.

    If the cooling is undersized and working properly of which both appear to be true... the machines will act as a dehumidifier, trying to take out the moisture in the air and probably causing an overload on the condensate drain and spilling over to the return.

    Residential or commercial, they BOTH need load calcs, those rules of thumbs will generaly get you in some deep poop.
    Still Crazy after all these years.

  8. #8
    Join Date
    Dec 2003
    Location
    Northern VA
    Posts
    619

    evap. coil

    Sounds as if you have a condensate drain problem.
    You will want to be sure that a trap has been installed-(usually in the install instructions) and also proper sized condensate piping.
    If you think that drainage is going to be an ongoing problem, (long horizontal runs sagging, algae buildup, etc.) put in a pump and be done with it.
    Business-wise, it sounds as if you have a credibility problem that you have to address. Get yourself back to being the ONLY AC expert on YOUR job.
    "Iron sharpeneth iron..."

  9. #9
    Join Date
    Sep 2004
    Location
    Memphis
    Posts
    2,502
    Originally posted by koolaid747

    the machines will act as a dehumidifier, trying to take out the moisture in the air and probably causing an overload on the condensate drain and spilling over to the return.
    I have a hard time believing that the drains are all installed correct & that a unit is pulling so much water out of it that a 3/4 pvc drain isnt capable of draining it. That would be a LOT of water.
    Life is like a jar of jalapenos. What you do today might burn your ass tomorrow.

  10. #10

    Angry Evaps

    If the unit is too small to handle such a high heat load would the unit flood and act as rainfall into the return air box. I was unable to get readings since he let me go but seeing that the evaps are just really sweating on both sides of the A coil would we need another system or larger one to help with the problem at such high heat and humidity. And yes the drains are properly run with traps and cleanouts and the are draining out of them. Both systems are having this problem.
    I just want to go back and tell him that the systems would cause problems if we went to small, and he suggested we wait till the building was complete before adding another system. But he was pissed off and fired me and told me he was getting someone else to finish.
    So now what?

  11. #11
    Join Date
    Dec 2003
    Location
    Northern VA
    Posts
    619

    evaporated contract

    I've had this happen when during construction especially with drywall sanding, the coil fins clog with very fine dust, but the coil faces look clean (from the condensate running down it).
    I know this sounds very basic- but is it possible that someone removed a dirty filter and took a little too long to replace it?
    These days there can be a real communication problem among the trades, especially where drywall artists are concerned.
    Sometimes the superintendent will change the filters, and sometimes simply remove it altogether, and alot of dust gets in in a little time.
    Sorry to hear of your termination- but be assured that a diligent mechanic will always land on his feet in this trade.
    Good luck.
    "Iron sharpeneth iron..."

  12. #12

    Thank You

    Thank You "Atmosphere" for you encouragement.
    Since i started my small business I prided myself on excellant service and installation.
    I have not had a complaint yet.
    But like they say there is always a first.
    I do not advertise but by word of mouth. My sales have trippled in the last three years.
    Now this
    I will try not to let this get me down.

    Stay Cool all


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