HVAC Master Class in Chemistry: Atila Novoselac on Ozone, CO2, Particle Filtration and Black Goo
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- čas přidán 21. 04. 2024
- Atila Novoselac is an awesome mentor of mine, and a treasure trove of building science secrets. He operates test homes at University of Texas at Austin, and knows WAY TOO MUCH about what happens when you run an HVAC system fan on vs. fan auto. For super nerds, this is going to be an all-time mind blower.
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This is great. Love these deep dives.
My eyes glazed over a few times during the video, but I got the gist that AC has a number of inherent issues that are challenging to solve. Thanks for attempting to make the presentation understandable to us non-scientists. So glad I’m building my new house in a moderate climate that does not require any mechanical cooling!
I can't say much about Mitsubishi, but the Trane variable speed air handler/compressor will reduce the fan speed and compressor speed if the humidity is above the setpoint. I know Trane and Mitsubishi work together, but I'm not clear how much they with together. But, I don't know how long the air handler will run after the compressor runs. But, the Trane variable speed compressor can run at lower speed than the Carrier which operates the other half of the house. The Trane is definitely more efficient at reducing humidity, but e can't say which is better at removing other chemicals.
ramping down, inverter heat pumps (at least the ones i know) do that. for eg mine here start ramping down once they get within 2c of target temp. also with the fan (if on auto). obviously they will run constantly at the lower speed if the don't hit the set point. a lot of these units use DC motors (for efficiency) and they tend to struggle with torque outputs at low rpm. so they don't go to very low rpm which you can do with an ac vfd/vsd.
Hi Corbett! I have a few questions about the video:
1. By what approximate percentage would the indoor particulate matter concentrations have fallen if the range hood fan would have been running during the toaster and cooking tests?
2. How much further would the particulate matter concentrations have fallen if a make-up air system had also been present in the kitchen and turned on when the range hood was on?
3. Where in the shown plan would you have placed the make-up air supply grills and how much air would each one of them supply (I’m guessing there would be more than one supply duct)?
Are these questions answered in a later video?
Hey Ryan-
1. Most of them, if not all
2. Zero effect on particles, all about pressure (if there’s a nasty pathway for make up air instead of a filtered one then yes it would get dirtier)
3. No wrong answers, but I’d put it close and make it big enough to drop the velocity to 300 fpm.
Corbett, this was fantastic! Your explanations made it do much more applicable
Great to hear, thanks buddy
Very useful commentary, Corbett. Thanks!
Hey thanks Lew my man
Great video! 14:00 - also, ductwork especially flex ducts, positively charge those particles which may help this issue.
It’ll certainly grab more stuff, which I’m not sure is helping or hurting.
seems like best,
for controlling both humidity and contaminates,
would be running both FAN and COIL at 100% duty cycle,
with cooling capacity control by variable refrigerant flow.
Agreed
@@HomePerformanceWhat about the evaporator coil redepositing its collected water vapor back into the home if the thermostat is set on fan? My buddy says he’ll get clients who complain about how humid their homes are. He said all he does is show up, and he’ll just turn their thermostat to auto, and problem fixed. It makes sense, with the fan constantly running, it pushes moisture back into the home because that air crosses over the wet coils. Then there is also the issue of dirtying your ducts way faster because the fan is constantly running too… Sounds like both have their pros and cons. Great video btw!
@sneakypete1200 sounds like your friend is forgetting to install a good filter (which makes the ducts dirty) and a dehumidifier (which solves the reuptake problem). Sounds like he works on conventional homes, where you can forget those things and no one would notice.
@@HomePerformance absolutely, and these conventional homes outnumber high performance homes by the millions. And most of these homes just have a furnace media filter, and no filters on the cold air returns. Or vice versa. I’ve never seen both. Plus, the majority of people do not add on whole home dehumidifiers to their HVAC’s. So for these regular homes, it would probably be best that they don’t use fan mode then…?
@sneakypete1200 correct, but why would they think of it in the first place?
Municipal wastewater systems need an extra set of pipes for high chemical pollution wastewater - the stuff coming off HVAC systems shouldn't be going into the general wastewater with ordinary domestic greywater and blackwater. It needs specialty processing for the high concentration of PFAS and other exotic toxins.
3:58 I think you meant to link to the thanksgiving day video
Thanks for the series and deep dives
You’re welcome and yes it’s linked at that mark
No clue what I’m talking about here. Is this an argument for separating ventilation from heating and cooling or adding dehumidification after the coil? Proper filtration always seems a good idea. I think we still rely on gravity to remove moisture from the coil, which seems a bit archaic; is there a more rapid and efficient approach to removing moisture from the coil? Is there a coating that can be applied to the interior of ducts that would make them less able to hold moisture?
I just emailed my Mitsubishi rep to find out if we can program the system or thermostat to shut off the fan motor for a few minutes to let the indoor coil drain. I'll let you know what I find out.
Nice KP
so fan on or auto?
If you have a insulated roof could you use a mini split in the attic to stop the vapor drive problem?
Mini Splits do not dehumidify well at all.
You are better off adding a small supply or return near the top of the roof.
@@ZergZfTw or adding a dehumidifier with the split. A conventional one, depending on the cubic feet.
@@sp1200M3D that can work just as well, but it's another expense to buy and maintain. A few feet of duct is basically free.
@@ZergZfTw no doubt, just gotta know what you’re doing. I wouldn’t advise it be a DIY with no HVAC knowledge lol
What about a UV light for water filtration?
I believe the side effects for human health are a lot different there, since tapwater won’t have thousands of chemicals in it waiting to be reacted into something else.
@@HomePerformance Thank you for your reply. However, when you say "the side effects for human health are a lot different there"... do you know of any harmful side effects, or that it just isn't a good idea to have a UV light for a water filtration system because we don't have enough info or study on it?
@gilbertsolis8539 there are already chemical disinfection methods at work in your water, so it’s probably just more of the same.