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Humidity Problem

of information to go on.It would be nice to know what your
pressure and temps were at the condenser and evaporator.

Also would be nice to know what your wetbulb temp were as well.

Oh well being we're just guessing here.I would have to say it possible you have an oversize metering device or the orfice is not seating properly.

Happy hunting.


  • Jesse Markeveys
    Jesse Markeveys Member Posts: 9
    Humidity Problem

    I recieved a service call today for a problem about a cooling system that was not removing any humidity. The customer had a hygrometer which told them the humidity level in the house (It was at about 61% RH) I checked the system out to make sure that the evap. coil was below the dew point temp. of the air; it was. I then hooked up my guages to get an accurate representation of the system proformance. The system was equipped with an orafice. My superheat was next to nothing but all of my other measurements checked out (Such as subcooling, proper condensing temp, and proper evap boiling temp). The only other measurement that stuck out was my temperature drop across my coil; it was 10 deg. With no superheat and a low delta t I figured that it was a safe bet to check out the evap. coil for blockages. The coil checked out fine. My next try was to slow down the air flow and see if I could get a better temperature difference plus remove more humidity. I slowed the airflow down to the lowest fan speed and noticed a slight increase. I also did an air side equation and noticed that the system was removing around 18,000 Btu/h when it was reated for 24,000 btu/h. I know that with out knowing exactlly how much cfm I am moving that equation is a little useless. When I left the residence the humidity level was down to about 54%. I know that most systems are designed to runaround 50%. But the customer swears that he used to get his humidity level down to 40%. Is it true? I don't know! My question is; did I look past anything. Any sugestions on how to solve this problem more thoroughlly?
    THank you
  • Empire_2
    Empire_2 Member Posts: 2,343
    Just a thought....

    Make sure the evap matches the condenser and check out what orifice is installed. There should be some king of S/H on the outlet of the evap. If not, the ref. has not boiled off and thus total capacity is not being utilized. As don stated, some actual measurements would be nice and while your at it give us some equipment models and manufacturer. One more note,...since you tried slowing down the blower when you in fact had 0 S/H it would have made the problem worse as far as S/H readings. Assuming you had a 90* day at 64* wet bulb temp inside, you should have roughly a 9* S/H @67 psi. and a suction line temp of about 48*. I am very curious what the suction pressure was.....

    Mike T.
  • Techman
    Techman Member Posts: 2,144
    Hardly any superheat!

    Jesse, I agree with don and Mike T , more info is needed. Superheat is a good thing and you don't have much,so lets figure this one out!By the way Mike T. no more ripples on my bends ,Thanks to you!
  • Empire_2
    Empire_2 Member Posts: 2,343

    Glad I could help. I have the same Yellow Jacket bender as you have and I ran into the same problem.........I tried EVERYTHING and the luckily came across the secrete to no ripple bends..;-)

    BTW/...Spit will still usually work.........:-0

    Mike T.
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    Slowing the Blower?!


    Hold on there buddy, and let's a step or two back from the system!

    Hear me out on this one... PLEASE!

    A liquid/refrigerant (saturated) mix is present in the evaporator...

    As heat from the conditioned space passes through the evaporator coil, heat is transferred to the refrigerant...

    This causes more of the liquid refrigerant to boil off into a vapor...

    If the amount of air moving through the coil is reduced, the amount of heat being added to the refrigerant will also decrease...

    Less heat being added to the refrigerant will make it take longer for the liqdui refrigerant to boil...

    This will case the superheat in the evaporator to drop.

    If there is already no evaporator superheat, this means that the quality of the refrigerant is going to be more and more liquid and less and less vapor...

    More liquid (any liquid for that matter) leaving the evaporator and entering the compressor is a VERY VERY VERY VERY bad thing.

    Now, as far as the piston goes... The piston is determined by the condensing unit, not the air handler. So, you should give the manufacturer a call and ask them what the correct piston should be for the condensing unit you have. If the piston is not correct... change it out.

    Keep us posted.
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