Hi, i'm brian with hvac school hvac, school podcast, hvac, our school comm. That's a mouthful making this video in conjunction with true tech tools, comm because they have really great tools like the tesco pixel by smart probe, thermo hygrometers that I'm demonstrating here. This video is going to be about something that I noticed with the 605 eye and it just kind of struck me as something that probably a lot of you are going to notice and think this is really weird and actually initially when I first started kind of Wrestling with this, I sort of understood what was going on, but not really, and I reached out to Jim Bergman and we had a conversation, and he gave me this description of how he explained it to his students, and I thought it was a really good description. So I thought I'd Rob it and make a video of it.

Of course, it's you know, what's what's a little robbery between friends right when you're, using the test fit of 605 eyes with the smart probes app like I happened to be right now, verifying delivered capacity. What you're going to notice is that this supplier, relative humidity, is really high and you can see the return. Air relative immunity is actually pretty low. Strangely enough, it's actually kind of dry here in Florida, probably because the state's on fire right now, but you can see this - is where my probe is here and my supplying.

And then I've got my other probe hanging down here below the return. And so the question is: why is my relative humidity so high and the supply? Doesn't that seem like a problem, in fact, in previous testing, that I've done, I've actually seen it significantly higher than that almost at 100 % relative humidity? So what gives so this right now is. Reading 55 degree drive volt supply air with 88 percent relative humidity, and the question is: why is that? Because the typical thinking would be well, we've got this air mass clinging over the evaporator coil, it's reaching dew point and it's dropping moisture. So the moisture is draining out the drink right now we're draining water outside.

So if we're draining water outside, why is the relative humidity going up it's coming in at 40 percent relative humidity and going out at 88 percent relative humidity? So why is that so we're going to do a demonstration that Jim Bergman suggested that easy to do in his class, but he hasn't done a video of it yet and I'm going to we're going to say this. Sponge represents air. It doesn't really look like air, but and we'll say that the size of the sponge or how much it's compressed represents the temperature of it and then the water represents the relative humidity or the moisture of the air okay. So the water is the moisture the sponges.

The air, how big it is, is the temperature so right now, this sponge is at 81 degrees, we're going to say that. Essentially, this is a dry sponge. It's not dry, but it's mostly dry doesn't have much moisture relative to the overall capacity that sponge can hold. Ok, so relative humidity, 100 % relative humidity for this sized sponge would be it completely saturated.

So this would be 100 % relative humidity. Totally saturated sponge to sponge is at a hundred percent relative humidity, based on its size. So I'm going to squeeze out 60 % of its water. Now we're going to say that's forty percent relative humidity, so it's forty percent of the water that this air can hold and it's coming in full-size it's coming in at 80 degrees.

Seventy nine point: seven degrees dry bulb right now. Some limbs of the coil hits the coil and, as I hit that coil the air gets colder and that temperature drop is represented by making the sponge smaller. So by squeezing it so now the air. Now the sponge, which is the air in hold less moisture, I dropped a bunch of moisture, but now it's at about a hundred percent relative humidity.

It had to be at 100 % relative humidity in order to drop moisture the Odom's an and had to be at 100 % relative humidity in order for it to drop moisture, because if it wasn't that it wouldn't have dropped moisture. So when it's touching that coil it's at a hundred percent relative humidity now the trick is that not a hundred percent of that air actually made good contact with the coil, so it didn't go to one hundred percent relative humidity. It only went to eighty eight point. Eight, and so, instead of squeezing it all the way, I'm going to let off it a little bit right now, and so this represents eighty eight point: seven percent relative humidity, because it's eighty eight point, seven percent saturated it goes out into the air stream and as It comes out and as soon as it into the dots as soon as it goes out, the duct into the rest of the space okay back over here.

As soon as it goes out the duct and back into the rest of space. Then it's allowed to warm up again and now it's lower than it was before. If you remember, I started with it at forty percent relative humidity, I went and I squeezed some out and then it was. It remained at eighty eight percent relative moving in the duct and then when it got AlphaDog, then it expanded and the question that my cameraman asked me when I first proposed this was well.

Why doesn't wiesen the inside of a duct mold great? Well, the reason is is because the inside of a dock, when you're in cooling mode is going if anything is going to pick up heat, not lose heat. So if the temperature outside of the duct was colder than what was in the duct, then it could condensate inside the duct but doesn't happen because obviously we're including those that's the point. So that's the reason why your supply air temperatures will be near 100 % relative humidity, in fact, any differential between 100 % and what you actually have displays, how much what we call bypass factor or bypass air is making it into the supply air stream. So if we had no bypass factor, if all of the air was reaching 100 % relative humidity, that it would still be a hundred percent relative humidity when it hit the duct, the fact that it's not all 100 % relative humidity either means that the coils, not A dew point, which we know that it is a dew point.

So that means that we have that percentage of air bypassing. So it doesn't mean that it's like bypassing like it's going around the coil. It just means that that percentage of air isn't making full contact with the coil, isn't reaching you point or 100 % relative humidity, which those are the same thing. You point hundred percent relative humidity or the exact same thing.

In fact, when you're dry bulb, temperature wet bulb, temperature and dew point are all the same. Is 100 percent relative humidity, 100 percent relative humidity, a lot less than 100 percent relative humidity, see what I did. There see still one percent relative humidity here when the air gets colder, so it's still totally saturated as long as water is coming out, 100 % relative humidity air, but as soon as it heats up and expands boom can hold a lot more again now. This is like 10 percent relative humidity, just to be a little more detailed in the description for those of you who want that sort of thing.

I wanted to plot this on the second metric charge and actually show it in action. So if the air coming in is 81 degrees, so the return air is 81 degrees. Dry bulb at 40 point five percent relative humidity, which is what we were showing early on when we were looking at the smart probes app. So we plot up to the 40 % line from 81 degrees and then go right to see the grains of moisture and you can also, if you go further, you can see the dew point, but the grains of moisture here are 64 and the dew point is Approximately 54 point five degrees, so this means that the air touching the coil must get to at least 54 point five degrees Fahrenheit for any condensation to a court curtain.

That means demystification. So if you don't have condensation, then you don't have demystification and vice versa. This also means that the evaporator coil itself has to be colder than 54 point five. If it's not colder than 54 point five, then the air can't get to that temperature.

So we're talking about dew point we're actually talking about the temperature of the air. Achieving dew point now, when we go into the supply, we're measuring a 55 degree, drive all the supply air temperature in the doct above the unit and we're reading it about two three feet above the unit and it's now reading 88 % relative humidity and the point Of this whole, video is kind of to demonstrate that that 88 percent relative humidity isn't a problem, because when you look at that, a lot of texts are going to. Thank. Oh, my gosh.

That's an issue, but if we plot that over to the right, we can see that the air now contains 56 grains of moisture per pound instead of 64, like it did before. So that proves that dehumidification is in fact occurring and the reason that the supply is at 88 percent relative humidity and not a hundred percent relative humidity is due to oil bypass factors. So not all of the air is actually coming in in solid contact with the coil duct gains, meaning that there is some dry bulb temperature added, even in that short piece of duct and blower gains, because the blower actually adds heat so based on what we know. Because we see a change in the grains per pound of dry air, we know that it's dehumidifier.

We also know that we have some bypass factor. We have some gains, because our relative humidity is 88 % and not 100 percent, which is what you would expect. I said that really animatedly like so what gives why do you think that is, let's say your tribal temperature is 80 degrees. If your wet bulb temperature was also 80, then that would mean that you're at 100 % relative humidity or if you're at 100 % visibility humidity.

That would mean that your wet bulb and dry bulb would be all the same. Isn't that interesting? What would it be if you were at a hundred percent humility, which is what you said several times? Is that what I said yeah they need to be like me, oh, I think. Then you just feel like everything I do is so bad, I'm the worst one hundred percent relative humidity, which means that whenever you go to a family reunion, all you do is talk about about yourself, but it's only a hundred percent. If everybody else talks really good about themselves, because it is relative right if you're in a bunch of other to humble team, now you're doing reflection twice so allative relative, humidity, humility, oh right yeah, I think we just lost the entire audience.

In addition to enjoying squeezing sponges, I would also suggest that you subscribe to the YouTube channel here up there. No, no, no! You can't so don't you just move the camera. Is it in shape? Hey how this works? Is it stays in one place on the screen? So you subscribe over there, no no now you're not supposed to move the camera. That's not how the sports.