mlparham Posted June 11, 2016 Report Share Posted June 11, 2016 . . . From the Florida Power and Light website: Another reason to keep it on ?auto? Setting your A/C fan to auto also helps provide better dehumidification. Have you noticed how moisture from the air condenses on the outside of a cold drink on a humid day? Your A/C unit captures moisture the same way, helping your home feel more comfortable. When the fan cycles off using the auto mode, moisture has a chance to drip from the cold cooling coils into the condensation pan and then drain outside. However, when the fan runs all the time in the ?on? setting, less moisture has a chance to drip and drain outside. Instead, some gets blown back into the air again. FL power & light wins the award for the most stupid paragraph I've read all week, and it's been a week full of stupid paragraphs. I will agree that it is a simpleton paragraph but the facts are correct. We likely all know the owner of an HVAC company. Just ask him or her. The answer will be do not run the ac fan in the on mode during the cooling months. Link to comment Share on other sites More sharing options...
Jim Katen Posted June 11, 2016 Report Share Posted June 11, 2016 . . . From the Florida Power and Light website: Another reason to keep it on ?auto? Setting your A/C fan to auto also helps provide better dehumidification. Have you noticed how moisture from the air condenses on the outside of a cold drink on a humid day? Your A/C unit captures moisture the same way, helping your home feel more comfortable. When the fan cycles off using the auto mode, moisture has a chance to drip from the cold cooling coils into the condensation pan and then drain outside. However, when the fan runs all the time in the ?on? setting, less moisture has a chance to drip and drain outside. Instead, some gets blown back into the air again. FL power & light wins the award for the most stupid paragraph I've read all week, and it's been a week full of stupid paragraphs. I will agree that it is a simpleton paragraph but the facts are correct. We likely all know the owner of an HVAC company. Just ask him or her. The answer will be do not run the ac fan in the on mode during the cooling months. It's incorrect for all of the reasons that Marc & Jim L already explained. HVAC techs are as susceptible to myth and folklore as anyone else. How much water clings to the coil at the end of a cycle? Two ounces? Three? Even if all of the clinging water were to evaporate back into the house (where it came from in the first place), that added volume of water pales in comparison to the pint or more of water that's removed in a cycle. Even if there were no purge cycle and you stopped the blower as soon as the cooling cycle stopped, that water would still sit there, clinging to the coil and waiting for the next cycle to start, whereupon it would evaporate into the air anyway, until it got cold enough to start condensing again. Link to comment Share on other sites More sharing options...
kurt Posted June 11, 2016 Author Report Share Posted June 11, 2016 I'm curious what "some" means......"Some gets blown back into the air again". Some? "Some" would seem to be substantially less what I put in the air when I cook rice for dinner, and way less than a human respirates in a day. I'm going to measure "some" and see if there's any measurable difference between auto and continuous. Link to comment Share on other sites More sharing options...
Marc Posted June 12, 2016 Report Share Posted June 12, 2016 . . . From the Florida Power and Light website: Another reason to keep it on ?auto? Setting your A/C fan to auto also helps provide better dehumidification. Have you noticed how moisture from the air condenses on the outside of a cold drink on a humid day? Your A/C unit captures moisture the same way, helping your home feel more comfortable. When the fan cycles off using the auto mode, moisture has a chance to drip from the cold cooling coils into the condensation pan and then drain outside. However, when the fan runs all the time in the ?on? setting, less moisture has a chance to drip and drain outside. Instead, some gets blown back into the air again. FL power & light wins the award for the most stupid paragraph I've read all week, and it's been a week full of stupid paragraphs. I will agree that it is a simpleton paragraph but the facts are correct. We likely all know the owner of an HVAC company. Just ask him or her. The answer will be do not run the ac fan in the on mode during the cooling months. Humph, I guess I should indeed ask an HVAC company owner. Let's see....Oh!...Yes, I do know one: Plumb Service Company. Founded in the early 90's by some deaf guy that works alone. Licensed in both AC and electric. Does just about everything but plumbing. I'll ask him. End of rant. Marc Link to comment Share on other sites More sharing options...
kurt Posted June 12, 2016 Author Report Share Posted June 12, 2016 Why not plumbing? Link to comment Share on other sites More sharing options...
Marc Posted June 12, 2016 Report Share Posted June 12, 2016 I considered it, but in Louisiana you must work for Master Plumber full time for several years (I forgot how many) before you can take the test. I didn't want to give up my other trades for that. Besides, I knew full well that no one would have hired me with my profound deafness. It was an in-law that took me on for electric and AC for a number of years and the framing job came to me through a good friend who had pull with his boss. For decades, I relied mostly on good friends, family, affirmative action (once) and luck to get jobs until I could become my own boss. Once I got on my own in the early 90's, I picked up whatever other trades I could. Marc Link to comment Share on other sites More sharing options...
tim5055 Posted June 12, 2016 Report Share Posted June 12, 2016 I'm thinking programming and modulating temps by cycling equipment differently than we've been doing is the next experiment. Get some Nest stats and go from there. Have you looked at Ecobee stats? It allows up to 32 wireless remote sensors. https://www.ecobee.com/ Link to comment Share on other sites More sharing options...
kurt Posted June 12, 2016 Author Report Share Posted June 12, 2016 Not in any detail, no. I think they're brilliant. Thnx. I checked and they're in all the big boxes. Readily available. This is what I'm thinking. Multiple sensors, maybe some zone baffles, and programming is how this is solved. Link to comment Share on other sites More sharing options...
Marc Posted June 13, 2016 Report Share Posted June 13, 2016 FTR, this is the only group of Hi's I can accommodate. Thanx for the input. Here's a different kind of fan. Very high volume but at low speeds. The smallest one is 100,000 CFM! Marc Link to comment Share on other sites More sharing options...
mlparham Posted June 13, 2016 Report Share Posted June 13, 2016 Methinks Florida Power and Light understands resid AC far less than the average AC tech. Very little water remains on the coil at any point in time. It drains away long before it becomes a substantial amount of water. Marc I did a short little test on my ac system today just to measure moisture output from the system fan running versus not running. The results were very interesting. Do you want 55% moisture air pumped into your for over an hour? Link to comment Share on other sites More sharing options...
rjbrown2 Posted June 13, 2016 Report Share Posted June 13, 2016 I haven't done this in a long time and I'm sure there are easier ways to crank it out on the internet, but I got out my Psychrometric Chart E-7 that came with my Thermal Environmental Engineering text by Threlkeld (1960s era) Assume upfront that 2 ounces of water (about 0.125 lb H2O ) remain available after the cooling cycle to go back into the air continuously passing over the coil. Assume at the end of the cooling cycle the air is sea level atmospheric pressure, 78F and an R.H. of 45%. I locate that point on the Chart and that the W (lbs water/lb dry air ) is about 0.0096. If we assume an 1800 sq ft home the the air volume is about 1800 x 8 ft = 14400 ft^3 with 8 ft ceilings and no furniture. So let's guess that we have about 10,000 ft^3. Using the specific volume on the chart at our point and inverting it, we get about 0.073 lbs air/ft^3. This results in about 730 lbs of air in our house. The increase in W is then about 0.125 lb/730 lb = 0.0002 lbs H2O/lb air. That bumps the number from 0.0096 to 0.0098. I have to estimate on the Chart, but it looks like about a 1% increase in the RH depending how long it takes to evaporate and assuming we don't start another cooling cycle before that is accomplished. The biggest error possibility I immediately see is the air volume estimate in the house. If I'm low the effect is significantly lower than 1% and if I'm high it could come closer to 2% I don't know how sensitive we are to 1 or 2% differences in R.H. Link to comment Share on other sites More sharing options...
mlparham Posted June 13, 2016 Report Share Posted June 13, 2016 Methinks Florida Power and Light understands resid AC far less than the average AC tech. Very little water remains on the coil at any point in time. It drains away long before it becomes a substantial amount of water. Marc I did a short little test on my ac system today just to measure moisture output from the system fan running versus not running. The results were very interesting. Do you want 55% moisture air pumped into your for over an hour? Link to comment Share on other sites More sharing options...
mlparham Posted June 13, 2016 Report Share Posted June 13, 2016 Methinks Florida Power and Light understands resid AC far less than the average AC tech. Very little water remains on the coil at any point in time. It drains away long before it becomes a substantial amount of water. Marc I did a short little test on my ac system today just to measure moisture output from the system fan running versus not running. The results were very interesting. Do you want 55% moisture air pumped into your for home over an hour? Link to comment Share on other sites More sharing options...
Marc Posted June 13, 2016 Report Share Posted June 13, 2016 Methinks Florida Power and Light understands resid AC far less than the average AC tech. Very little water remains on the coil at any point in time. It drains away long before it becomes a substantial amount of water. Marc I did a short little test on my ac system today just to measure moisture output from the system fan running versus not running. The results were very interesting. Do you want 55% moisture air pumped into your for home over an hour? Where is it being pumped from? Let me guess...the inside of the house? Marc Link to comment Share on other sites More sharing options...
Erby Posted June 13, 2016 Report Share Posted June 13, 2016 rjbrown just made my head hurt! Link to comment Share on other sites More sharing options...
kurt Posted June 13, 2016 Author Report Share Posted June 13, 2016 I'm kinda thinking along the lines of rjbrown. IOW, I don't think it matters. Link to comment Share on other sites More sharing options...
Jim Katen Posted June 14, 2016 Report Share Posted June 14, 2016 Methinks Florida Power and Light understands resid AC far less than the average AC tech. Very little water remains on the coil at any point in time. It drains away long before it becomes a substantial amount of water. Marc I did a short little test on my ac system today just to measure moisture output from the system fan running versus not running. The results were very interesting. Do you want 55% moisture air pumped into your for over an hour? More info. What kind of tool did you use and what, exactly, did you do? What were the moisture levels when the AC was running? What were they when it stopped running? Could you plot both the temperatures and the RH on a chart? I find it difficult to believe that you'd get moisture evaporating off of a coil for a solid hour. Link to comment Share on other sites More sharing options...
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