Heating, Air Conditioning, Fridge, HVAC/AC condensate


Hi Craig,

If I understand correctly, avg AC condensate is 0.3 - 0.5 gal/hr/ton.  I'm on the low side at 0.3 and I'd like to know if and how I can get more toward the 0.5.

I have a 3-bedroom rambler on a slab stick-built in 1953. The 1997 Carrier AC/furnace unit is in the middle of the house and the air vents run under the slab.  The compressor is on the side of the house with a 45 foot run for the 3/8 HP and 3/4 LP tubing.  The compressor is 2.5 ton and the evap coil is 3.0 ton.

Ever since the AC was installed it has cooled very well set on 72 deg F, but the inside RH is almost always around 60 in the summer.

Yesterday and today I tried changing the blower speed but only with modest results.  Outside temp was 94 deg F with RH about 50.  Thermostat was set to 72 deg F but it didn't get much below 75 and inside RH hovered around 62 percent. The low and med hi speeds both resulted in about 0.3 gal/hr/ton and hi speed about 0.27 gal/hr/ton.  On all speeds the pre coil dry temp was about 75 deg F and the post coil temp was about 55 on low speed, 57.5 on med hi speed, and 58.5 on hi speed as read about 6 - 8 inches from the coil.  The air filter was clean and everything seemed to be functioning normally -- except for the low condensate.

I've read that units after the early 90's are more energy efficient and, by default, are less condensate-efficient, but, gee wiz, I'd like to think I could get more than 0.3.

I also thought of low Freon, but post coil temps seem to be in line and, besides, it's been no different since it was new.

Is there any hope other than a new unit?

Thank you so much for your help.  I really appreciate folks like you who take the time to help others!


I am going to start this way...I can not tell, though it appears to be working ok, if the unit is properly charged from what you have told me.  There are more measurements required to do so.

Now, to understand the humidity and moisture is called Psychrometrics.  There is also a Psychrometric chart we use to determine moisture removal from the air, along with other conditions.  The chart will allow one to determine how much moisture is being removed when properly calculated.   

The amount of moisture removed has several factors.  The RH level is not the lone factor.  You have to keep in mind that RH% goes up as temp goes down.  The amount of water (weight) in the air does not change as the temp changes. Once the coil reaches dew point, the moisture will start to leave the air and attach to the cold surface The water then leaves the unit out the drain.  There can be more "gallons" of water removed from the air at at 78*F @ 60% RH vs. 72*F @ 60% RH.

The last thing is this, the human body will feel a difference in humidity quicker then temp.  It is possible to feel hot and sticky at 72*F 60% RH and feel cold at 76*F and 40% RH.

Here is a link where you can D/L an electronic version of the chart free.



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Craig HVAC Expert


I have been in the HVAC field for the past 18 years. I can help with most HVAC questions. I work on commerical buildings for the most part, and have yet to find anything I could not troubleshoot and repair, when repairable. I work on small 1 ton units to a 2500 ton chiller. Troubleshoot air flow, elect, and control problems. I attend regular classes to keep up with the latest and greatest.


I work on commerical sites, hospitals, gov't buildings. I can troubleshoot just about anything in the HVAC business.

5 years trade school, VFD training classes, Liebert factory training, some York and Trane factory training.

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