Another way to demonstrate this would be to fill a balloon and then put in a refrigerator and watch it shrink. The air becomes more dense which decrases its ability to hold water. When supply air mixes with warmer indoor air it quickly expands Which immediately increases its ability to hold more water.
For Florida, even, your CFM must be very low for that supply air and the temp drop from return to supply. holy cow. Absolute humidity if falling of course (buy a better tool please); but get your psychrometric chart out and graph this, there is no miracle here; also, error on 90% RH measurement is very high for this tool, be careful, please understand that.
Cool air is more dense, which has less ability or "room" to hold moisture, relative to it's volumn, volumn being affected by temp. Wait...what? Let me replay this a 9th time..
Great visual in explaining! Our company had a boss who would try to explain psychrometrics to the crew. Most of the crew would roll their eyes and ignore him. After he left we came across a few jobs with humidity and bio growth problems. There were a couple of guys who paid attention and were able to correct these problems. Every hvac company needs a guy like Bryan but many companies don’t deserve them.
If u want distance U could buy --- Fieldpiece Probes. They have greater distance. Like 1 city block unobstructed .See Norcals videos on fielpiece probe distances. Or a Air Probe from imanifold and a 900c Repeater Box for Mega Distance Like a 1/4 Mile with iconnect box. See my video on iconnect distance.
Little confused.....I took some measurement today with the alnor 6200d ...and 605is....1284 cfm with 52,437 btu/h...??? I took the measurements twice roughly same numbers......does this sound right to you...If not sure can you ask Bergman....thanks
Thank you for the explanation. I was wonder why my supply air at home is at like 99% RH at 56% at the air vent. I would thought the cold air coming out would be very dry with low RH.
What is great, you rob others, and present it and give credit to the original source. TY for being youtube robber video guy. Better would be to describe the compression of the sponge as pressure, which is related to temperature (increase pressure, you increase temperatures). Problem is that most watching aren't into thermodynamics, or care.
So, am I understanding this correctly? Air has water holding potential, the warmer the air, the more potential and visa versa; the colder the air, less potential. As warm moist air is pushed through and cooled across the coil, the less potential it has to hold moisture and this is reduced through each running cycle of the areas volume. Now the higher humidity in the duct is the blower blowing across a cold saturated coil and putting some of that moisture in the duct but the cooler air won’t necessarily absorb it. The hygrometer is picking up that extra moisture showing a higher humidity( almost a false reading) If you take the hygrometer to a supply vent it should show a lower humidity as it definitely will in the larger open area of the room. Of coarse these humidity readings will continue to drop as the air cools, losing its moisture holding potential. Btw: great videos!
Very enlightening, thank you for posting this video. I downloaded a copy of the psychometric chart from hvacrschool.com and when I opened the PDF using Windows 10, I got a notice saying, "Can not find or create the font "arial narrow". Some characters may not display or print correctly." Unfortunately, I can't read most of the chart. Anyone have any suggestions how I can get this chart to display correctly?
I would add the fact that the heat gain of the motor and friction of the fan blade will change your air properties. Rise in temperatures and lower RH% content value.
thanks man you saved my harvest from rotting while drying....I had a portable ac unit right up against my drying room to keep the temp down but I could not keep my humidity to an acceptable limit. I backed off my portable ac . made a duct system to my room and like magic or science the humidity dropped by 20 thanks for the knowledge. if you are ever in Toronto I got a nice bud for you to smoke
..and now for the guy who boosts fan speeds for airflow at the furthest supply and screws up all the great calculations we do .. Do another vid on airflow/ velocity and static pressure for a basic residential system and branch flow.
Really good visual and knowledgeable explanation. On a side note I have two new life goals.. one is to have 100% humility.. the other is for my supply duct to always have 100% humidity.
So, warmer air coming in through the return can hold more moisture, & the colder air can hold less. As the air passes through the coil it becomes colder and thus shrinking the air molecules and wringing out the water( condensation)making the relative humidity on the supply side high, because of lack of molecular space to contain water?
The air molecules stay the same size, and so do the water molecules. To understand why air has a capacity to "hold" water vapor, you need to look at it in terms of Dalton's law of partial pressure. For a nice round number, consider air at 100 kPa of pressure. Suppose we have a given air mass that is 1% water vapor, by molecule population, which corresponds to a humidity mass ratio of 0.0063. Per Dalton's law of partial pressure, the partial pressure of each flavor of gas is proportional to the molecule population fractions (i.e. mole fractions). This means our sample's water vapor partial pressure is 1 kPa. Look up water's boiling point at 1 kPa, which is 6.97 Celsius. Any hotter than this, and the water vapor is perfectly at home in vapor form, being mixed with the air. Any colder than this, and water will condense until the partial pressure is low enough to support the remaining water vapor in vapor form. 6.97 Celsius is the dew point of this air mass that is 1% water vapor by molecule population. If you increase the mole fraction of water vapor, you'll increase the dew point. The water will be at a higher partial pressure, and if it were contained in a vessel separate from the air, it will boil at a higher temperature at that pressure. This therefore increases the minimum temperature that can support that composition of air. At 2% mole fraction, the dew point will be 17.5 C. At 3%, it will be 24.1C.
Informative video. i need someone's help. i am facing a problem in laminar air flow system of operation theater, that there is too much moisture in laminar air flow while HVAC system works in summer. moisture levels is too high like water droplets fall from the Laminar air flow. plz guide me how can i control this. thank you
Here is some Joe-isms that I've seen in the field taking these measurement. 1) the higher the cfm/ton the higher the supply rh which seems to contradict the bypass factor theory. Case in point your mini split 605i video 2) the more supply %RH the lower the capacity. I guess because you aren't pulling as much latent out. Basically because you aren't stripping the air going across the coil below its saturation point because your coil is warmer and larger with today's high seer coils. 3) obviously the lower the supply air RH the more your capacity will be I don't pretend to know all of the exact reasons for this but would love to see some videos more in depth I think Supply RH can give a lot of info about the system if we understood it more.
Joe Shearer I think Case #1 in the ductless video was just a factor of runtime. I have experienced the opposite, but admittedly I have not used it on a daily basis. We are starting to do delivered capacity commissioning on new installs so we will have a much larger sample size to analyze soon.
To answer your scenario #1 by where an increased airflow creates a higher %rh in the supply air. What you are seeing is a function of the reduced amount of time in which the moisture in the air is allowed to contact the coil surface. The ratio of sensible capacity is always higher than latent capacity and will therefore continue to increase the air density, thereby resulting in a higher rh. If you are truly attempting to de- humidify, it is most helpful to have a source of re-heat, ie hot gas bypass or a hot water coil. This allows you reduce your LAT to a lower temp thereby removing even more moisture. Then the air passes over the re- heat coil and is brought up to the 55 degree neighboorhood and you now have dry, cool, and dense air.
The dew point is the minimum possible temperature for an air/water mixture with a fixed mass ratio between the air and water vapor to exist without condensing. If you cool it without mass transfer, it will cool to the dew point. By contrast, if you cool it with mass transfer, but without heat transfer, it will cool to the wet bulb temperature, or adiabatic saturation temperature.
Excellent explanation.
Great video as always. Is there anyway you can add this to your podcast.
Good not to hear Goodman bashing and cuss words once in a while.
Another way to demonstrate this would be to fill a balloon and then put in a refrigerator and watch it shrink. The air becomes more dense which decrases its ability to hold water. When supply air mixes with warmer indoor air it quickly expands Which immediately increases its ability to hold more water.
For Florida, even, your CFM must be very low for that supply air and the temp drop from return to supply. holy cow. Absolute humidity if falling of course (buy a better tool please); but get your psychrometric chart out and graph this, there is no miracle here; also, error on 90% RH measurement is very high for this tool, be careful, please understand that.
QL ... latent heat. QL=GD*CFM*0.68
Cool air is more dense, which has less ability or "room" to hold moisture, relative to it's volumn, volumn being affected by temp. Wait...what? Let me replay this a 9th time..
Great visual in explaining! Our company had a boss who would try to explain psychrometrics to the crew. Most of the crew would roll their eyes and ignore him. After he left we came across a few jobs with humidity and bio growth problems. There were a couple of guys who paid attention and were able to correct these problems. Every hvac company needs a guy like Bryan but many companies don’t deserve them.
What would be the ok relative humidity inside the closet where the handler is?
So say that was a fridge then the moisture would continue dropping?
Cut the sponge in half as temp drops
RELATIVE HUMILITY -- every relative is as humble as you are,,,,,, relatively.
I was racking my head over this ever scene I tried out my testo too.
Great explanation Thank You.
Curious how much the positive pressure on supply side/negative pressure on return also contribute to the phenomena?
your question is noted and i will answer it soon in my Q/A video
can anything be done for the Testo 605i to be able to pick up at a longer distance? thank you for making videos !
THE GENIUS REPAIRS not that I am aware of at this time
THE GENIUS REPAIRS can you do a live share via wifi?
If u want distance U could buy --- Fieldpiece Probes. They have greater distance. Like 1 city block unobstructed .See Norcals videos on fielpiece probe distances. Or a Air Probe from imanifold and a 900c Repeater Box for Mega Distance Like a 1/4 Mile with iconnect box. See my video on iconnect distance.
like it like always
good video
Ps. funny guys
Nice video! I always wondered that.
Little confused.....I took some measurement today with the alnor 6200d ...and 605is....1284 cfm with 52,437 btu/h...???
I took the measurements twice roughly same numbers......does this sound right to you...If not sure can you ask Bergman....thanks
Can you explain how blower speed impacts humidity? When you increase blower speed, do you have to add more R-410A?
Thank you for the explanation. I was wonder why my supply air at home is at like 99% RH at 56% at the air vent. I would thought the cold air coming out would be very dry with low RH.
What is great, you rob others, and present it and give credit to the original source. TY for being youtube robber video guy. Better would be to describe the compression of the sponge as pressure, which is related to temperature (increase pressure, you increase temperatures). Problem is that most watching aren't into thermodynamics, or care.
So, am I understanding this correctly?
Air has water holding potential, the warmer the air, the more potential and visa versa; the colder the air, less potential.
As warm moist air is pushed through and cooled across the coil, the less potential it has to hold moisture and this is reduced through each running cycle of the areas volume. Now the higher humidity in the duct is the blower blowing across a cold saturated coil and putting some of that moisture in the duct but the cooler air won’t necessarily absorb it. The hygrometer is picking up that extra moisture showing a higher humidity( almost a false reading) If you take the hygrometer to a supply vent it should show a lower humidity as it definitely will in the larger open area of the room. Of coarse these humidity readings will continue to drop as the air cools, losing its moisture holding potential. Btw: great videos!
I understand the sponge example and in or near the coil. How does this apply to a home? 88% dehumidifing is happening?
Very enlightening, thank you for posting this video. I downloaded a copy of the psychometric chart from hvacrschool.com and when I opened the PDF using Windows 10, I got a notice saying, "Can not find or create the font "arial narrow". Some characters may not display or print correctly." Unfortunately, I can't read most of the chart. Anyone have any suggestions how I can get this chart to display correctly?
I would add the fact that the heat gain of the motor and friction of the fan blade will change your air properties. Rise in temperatures and lower RH% content value.
thanks man you saved my harvest from rotting while drying....I had a portable ac unit right up against my drying room to keep the temp down but I could not keep my humidity to an acceptable limit. I backed off my portable ac . made a duct system to my room and like magic or science the humidity dropped by 20 thanks for the knowledge. if you are ever in Toronto I got a nice bud for you to smoke
..and now for the guy who boosts fan speeds for airflow at the furthest supply and screws up all the great calculations we do ..
Do another vid on airflow/ velocity and static pressure for a basic residential system and branch flow.
Really good visual and knowledgeable explanation.
On a side note I have two new life goals.. one is to have 100% humility.. the other is for my supply duct to always have 100% humidity.
So, warmer air coming in through the return can hold more moisture, & the colder air can hold less. As the air passes through the coil it becomes colder and thus shrinking the air molecules and wringing out the water( condensation)making the relative humidity on the supply side high, because of lack of molecular space to contain water?
The air molecules stay the same size, and so do the water molecules. To understand why air has a capacity to "hold" water vapor, you need to look at it in terms of Dalton's law of partial pressure. For a nice round number, consider air at 100 kPa of pressure. Suppose we have a given air mass that is 1% water vapor, by molecule population, which corresponds to a humidity mass ratio of 0.0063. Per Dalton's law of partial pressure, the partial pressure of each flavor of gas is proportional to the molecule population fractions (i.e. mole fractions). This means our sample's water vapor partial pressure is 1 kPa.
Look up water's boiling point at 1 kPa, which is 6.97 Celsius. Any hotter than this, and the water vapor is perfectly at home in vapor form, being mixed with the air. Any colder than this, and water will condense until the partial pressure is low enough to support the remaining water vapor in vapor form. 6.97 Celsius is the dew point of this air mass that is 1% water vapor by molecule population.
If you increase the mole fraction of water vapor, you'll increase the dew point. The water will be at a higher partial pressure, and if it were contained in a vessel separate from the air, it will boil at a higher temperature at that pressure. This therefore increases the minimum temperature that can support that composition of air. At 2% mole fraction, the dew point will be 17.5 C. At 3%, it will be 24.1C.
Thanks for the amazing content Sir!You help me a lot.Please dont stop making new videos
Thanks for the amazing content Sir!You help me a lot.Please dont stop making new videos
What I need to do to reduce supply air humidity, or room humidity.
I’m in school for HVAC and this video made a lot more sense than in the book. Thanks 👍
Wow! Great explanation! I was wondering why that was so high. Thanks.
Wow great job explaining! Thank you!
Key word is "relative".
As in relative to current temp.
Thank you for being so thorough...and for the comedic breaks. Keep it up!
Ever use enthalpy change to verify moisture removal across the evap?
Thank you for making these videos. You guys are great.
Best way ever to explain relative humidity: a simple sponge.
Cool concept Bryan, thanks for sharing.
Informative video. i need someone's help. i am facing a problem in laminar air flow system of operation theater, that there is too much moisture in laminar air flow while HVAC system works in summer. moisture levels is too high like water droplets fall from the Laminar air flow. plz guide me how can i control this. thank you
Aprilaire dehumidifier.
Here is some Joe-isms that I've seen in the field taking these measurement.
1) the higher the cfm/ton the higher the supply rh which seems to contradict the bypass factor theory. Case in point your mini split 605i video
2) the more supply %RH the lower the capacity. I guess because you aren't pulling as much latent out. Basically because you aren't stripping the air going across the coil below its saturation point because your coil is warmer and larger with today's high seer coils.
3) obviously the lower the supply air RH the more your capacity will be
I don't pretend to know all of the exact reasons for this but would love to see some videos more in depth I think Supply RH can give a lot of info about the system if we understood it more.
Joe Shearer I think Case #1 in the ductless video was just a factor of runtime. I have experienced the opposite, but admittedly I have not used it on a daily basis. We are starting to do delivered capacity commissioning on new installs so we will have a much larger sample size to analyze soon.
HVAC School please keep us posted on your findings I was speaking more on the newer high seer equipment with oversized evap coils.
To answer your scenario #1 by where an increased airflow creates a higher %rh in the supply air. What you are seeing is a function of the reduced amount of time in which the moisture in the air is allowed to contact the coil surface. The ratio of sensible capacity is always higher than latent capacity and will therefore continue to increase the air density, thereby resulting in a higher rh.
If you are truly attempting to de- humidify, it is most helpful to have a source of re-heat, ie hot gas bypass or a hot water coil. This allows you reduce your LAT to a lower temp thereby removing even more moisture. Then the air passes over the re- heat coil and is brought up to the 55 degree neighboorhood and you now have dry, cool, and dense air.
Relative humility! LOL
Great video!
Good video.
return rh at 58%
Great video
what is the dew point
The dew point is the minimum possible temperature for an air/water mixture with a fixed mass ratio between the air and water vapor to exist without condensing. If you cool it without mass transfer, it will cool to the dew point. By contrast, if you cool it with mass transfer, but without heat transfer, it will cool to the wet bulb temperature, or adiabatic saturation temperature.