Humidity???
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Thread: Humidity???

  1. #1
    Join Date
    Aug 2003
    Posts
    27

    Hmm

    I need some of your thoughts. Ive been reading what people having been writing and trying to figure out if my situation matches.

    I have a 725 square foot brick and concrete block house on a cement slab in Southwest Lower Michigan, a mile from Lake Michigan. The duct work runs overhead with a centrally located return. I use the house as a second home all year long.

    In March I had the furnace replaced with a Lennox G60OUHV-36A-070 and XC13-018-230 A/C added.

    The company said they would come out and check the A/C on the first hot day to make sure there was enough of refrigerant in the unit. The tech that helped with the install added some gas and lower the fan speed to one from the factory setting of four. After two hours of running no condensation came out of the drain tube. The house could be cooled to 71 degrees with six adults, but too much humidity. I called for service.

    The supervisor tech came out said it was over charged and fan speed too low, after he checked temperatures in the ducts before and after coil and the gas in A/C. The same thing happened again.

    So I raised the fan speed to three. Now water always runs out of the condensation tube. When the tech called me and asked how things were working after his changes, I told him what I did. He said sometimes, you must do that in your situation. The house feels better now.

    What does that mean, my situation? Is the house too small for central A/C? Too much concrete? 4 inch duct was changed to 6 inch flex duct, but the opening in the ceiling stayed the same.

    I had a 14,000 Btu window unit that did fine after a day of running. On the third day humidity would drop to 45% in the living room. Now it wont go lower than 60%. They wanted to sell me a 2 ton unit, I insisted on the 18,000 Btus because 14,000 did the job. I know that A/C must run in order to remove humidity and I said that to the salesman.

    I have the Honeywell t-stat that you can call and check inside and outside temperatures. Its a great t-state for second home owners. Most of the time the house didnt get above 80 degrees, with shades down. I have lots of trees on the West side of the house. I give the house at least 12 hours of cooling before arriving.

    Last question, what was the reasoning behind letting the fan run at 50% for 30 seconds after the A/C shut off? Default setting.

  2. #2
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,817
    From what I can see of the blower tables, you want the lowest possible setting and even that is too much for your 1.5 ton unit. Set at tap 1 with - airflow adjust, you'll be a bit over 900 CFM where 600 is the max for good dehumidification on the 1.5 ton unit. Now, if your dealer wants to solve the problem, he'll ignore Y2 which is 2nd stage heat and use only Y1 which is low speed for a 2 speed outdoor unit. If he uses tap 1 and the - air adjust, he'll be just a hair over the desired airflow. I'd use profile A on the cooling ramp up for max dehumidification. Running the blower after for 30 seconds gets about .1 SEER point more from the A/C.

    Have your dealer look at the blower chart and try my idea, bet that will decrease your humidity!

  3. #3
    Join Date
    Dec 2005
    Posts
    1,899
    Chorusppp,

    What balonie said is true.

    My recommend to you is this.

    Set your dip switches (cooling side) as a three tons cooling CFM. But you don't connect any wire on the Y or Y2 terminal. That makes the furnace thinks you only run fan, which will produce 1/2 the total CFM of the cooling, which is 600 CFM to match with you system. If you want to reduce further, then set the dip switch for fan only at a lower CFM. Window unit runs with very low CFM per ton comparing to the central air. I run my central air at 520 CFM for a 2.5 tons to remove moisture in the SE texas

    Hope it helps

  4. #4
    Join Date
    Aug 2003
    Posts
    27
    That's the reason why the first tech lower it to speed one. He said the furnace was set for a 2 ton unit. Is that why they wanted to sell me a 2 ton unit? Was I wrong for wanting a 1.5 ton unit?

    Was my coil freezing? No ice formed on the tubing. It didn't seem like the air flow was restricted.

    I don't have the books in front of me, they are at the second home. Sounds like your suggesting a constant fan speed, not the 82% for 7.5 minutes, than 100%. It's still set to the default setting.

  5. #5
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,817
    The furnace is capable of 1200 CFM (3 tons) on high. Nothing wrong with that other than an installer realizing that and using the blower table to determine what airflow you need. The idea of using Y1 only will still let you use the ramp profile for extra dehumdification. ppp's idea will achieve the same airflow.

  6. #6
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,231
    Do your best to slow the fan to get a real cold coil to max moisture removal. After your are do your best to improve humidity control with your a/c, add a high eff. dehumidifier for provide absolute humidity control without over-cooling. You can turn off the a/c and maintain <50%RH for fraction of the cost of trying with a/c. Dehu TB

  7. #7
    Join Date
    Aug 2003
    Posts
    27
    At fans speeds one and two after two hours of running, no condensation was coming out of the tube. The house was getting clamy. The A/C ran for 5 hours straight. When it stopped and started up again water came out for a while and than stopped, but the A/C was cycling because it was evening. The same thing happend the next day. Both days were over 90 degrees, high humidiy.

    That's why I raised the speed to three. Because condensation will come out all afternoon and the A/C would cycle. The house fells better, but I think it could do more.

    When condensation stopped, doesn't mean the coil is starting to freeze, causing the humidity to go up? There was no ice forming on the return tube by the A/C unit. Or does that happen only when there is s shortage of gas? Could there be something wrong with the A coil? I hope not. The furnace is on its side in the attic, with the coil designed for that operation.

    I realized that this would require a lot of fine tuning and monitoring, but I'm running out of hot summer days.

  8. #8
    Join Date
    Aug 2003
    Posts
    27

    Hmm Why doesn't mind work like that?

    Originally posted by just_opinion
    Chorusppp,

    What balonie said is true.

    My recommend to you is this.

    Set your dip switches (cooling side) as a three tons cooling CFM. But you don't connect any wire on the Y or Y2 terminal. That makes the furnace thinks you only run fan, which will produce 1/2 the total CFM of the cooling, which is 600 CFM to match with you system. If you want to reduce further, then set the dip switch for fan only at a lower CFM. Window unit runs with very low CFM per ton comparing to the central air. I run my central air at 520 CFM for a 2.5 tons to remove moisture in the SE texas

    Hope it helps
    The furnace was set to speed one, but condensation stopped coming out of the drain tube. The same thing happend on speed two. It's not like the A/C run 10 minutes and stops for a 20 minutes and then runs 5 minutes and stops. I should have no problem on speed one, but I do. I'm puzzled??


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