Heating, Air Conditioning, Fridge, HVAC/AC condensate
QUESTION: Hi John,
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!
The thing you have to look at for the Freon level, as far as a quick check if it is close, is the temperature drop from the return air to the supply air which yours is under 20 degrees and we like to see 20 to 24 degrees on an R-22 system.
As far as humidity control, that is not a function of the Freon charge ( since it is close ) as much as the sizing of the equipment for what you want it to do. A swimming pool de-humidifier is really just an undersized air conditioner with a little bit of a mis-matched coil indoors.
The way it works is the longer the AC runs on each cycle the more humidity it removes. What is the model and serial number on the outdoor unit and the indoor coil? I will give you a list of data points that you can have a service company record and I will be able to tell you the state of your equipment and if it needs the Freon level adjusted. These all need to be taken at the same time and after the equipment has been running at least 10 to 15 minutes.
1)high and low pressure
2)ambient (outside) temperature
3)suction line temperature
4) liquid line temperature
5) return air temperature
6) supply air temperature.
Keep in mind that if and when you replace your equipment that R-22 is phased out and the new equipment will be using R-410a. Which although it is more temperamental and harder to work with, has much higher values when it comes to efficiency in change of state from liquid to gas and visa versa. R-22 maximum split from return air to supply will be about 24 degree's, R410a will be 30 degrees or more.
If you want to follow up with my help on the charge, I will be happy to, just let me know.
---------- FOLLOW-UP ----------
QUESTION: Hi John,
Thank you so much for your help!
Info you requested:
The furnace, compressor and evap coil is a Carrier "matched" system, except that the coil is not Carrier since the HVAC folks said Carrier was having quality issues with theirs at the time.
Furnace: Carrier Model 58ZAV-096-1-12 Weathermaker 8000 Delux High-Efficiency Downflow/Horizontal Gas Furnace (1200 CFM, 4 blower speeds)
2.5 Ton Carrier Outdoor Unit:
Serial: 0497E04298, Model 38TRA030320
R-22 charge, 6.25 LBS, 2,83 Kg, Piston ID 67, 00 N/A,
Pressure 300 PSI Hi, 150 PSI Lo
3 Ton Inside Coil:
ADP Stone Mountain GA, HA03236C175B16057
With reference to more than a 20 deg temp difference and more condensate, could you please comment on a couple of references I've seen. I'd just like to understand more about the available info:
I found a chart on one of the HVAC sites that gives the appropriate temp difference based on the return air dry bulb and return air wet bulb. I think it came from CA Title 24 or something like that. For example, 75 deg dry and 65 deg wet equals 17.1 deg difference between return dry and supply dry, or in this example, 57.9 deg supply temp (post coil). It's been right on with all my readings at various times of the day and at various blower speeds.
BuildingGreen.com has an on-line condensate calculator that seems to match my results pretty close. You plug in outside temp and RH, inside temp and RH, AC tons, outside air makeup percent, and it gives you Gal per hour/day condensate.
Other sites suggest 5-10 gal/day or 0.3-0.5 gal/hr/ton. I seem to be in the middle and low end of those, respectively.
Relative to sizing, run time, and Freon: The HVAC folks who "designed" the system determined that the 2.5 ton compressor and 3 tom coil was the best match for my house and seems to be typical for my size and style house. When outside is upper eighties and above, it runs constantly and when above 90-95 outside, it can't quite keep up and inside starts to climb, usually hovering about 20 deg less inside than out, and I understand this to be about the norm and sized about right since anything above the upper eighties in the DC area is a heat wave.
I don't quite understand how freon charge is not a factor for condensate, since condensate depends on low coil temp and low coil temp depends on freon charge - all else being equal. Could you explain that in a bit more detail.
Meanwhile, I seem to get the best and same condensation rate with the blower speed at low or med-hi, although low gets the post coil plenum icy cold (with a bit of condensation forming on it, while med-hi gets it a bit less cold. On the HI settings, I get about 10 percent less condensate and the plenum is a bit less cold yet. Which setting would you suggest as the best all around with the system operating as it is now.
If I get the HVAC folks to come out, what type of tech should I ask for to be sure I don't end up with the average Joe who just checks the pressure and adds a bit of Freon "just to be sure" and says "good to go".
Thanks so much for your help!
You need to read the sentence as a whole as far as the Freon charge reply I sent you. I stated "As far as humidity control, that is not a function of the Freon charge ( since it is close )as much as the sizing of the equipment".
Meaning that from the data you sent I deduced that the amount of refrigerant in your equipment must be very close to the correct amount, therefor the sizing is more of an issue in so much as my answer was concerned.
Ask for the "senior" or lead tech and always make sure when using an HVAC company that the tech(s) are N.A.T.E certified. Also contact your utility company and ask them what programs they have or arrangements with the local companies for recommended contractors and or certifications they promote and/or require in your area.
When you call ask for the lead tech or owner or manager and explain to them what you need them to return for, why and make sure they know the list of data you want collected (with you over their shoulder) and why. They should not have an issue with you being helped by a Teacher/Expert type person that is unbiased and is only interested in helping you communicate and work with their company to resolve the issue you called them out and paid for them to resolve. That also should insure that you get the more/most senior tech so that they look their best in the eyes of some one who would actually be at or above the level of any teachers or Proctors they might encounter in their line of work.
Also ask them if the senior tech would write a small summation at the bottom of the work order with their findings and any recommendations and why.
Hope that helps. And don't forget to rate any and all answers that you get from any and all categories of All Experts.com as that is our only reward for the countless hours we help out. I will say that I have had one questioner that used our donation option and threw me a few bucks for what we charge pretty good money for during the business hours, I got lucky today and just got home with only a 10 hour day before I got on here.