The Danger of High Airflow in HVAC
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- Опубліковано 4 вер 2024
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I have a two stage single compressor that runs 70% in first stage and 100% in second. For these systems you wire Y 1 to Y and Y 2 to the BK terminal which runs the fan at 80% in first stage. This means you have more CFM per ton in first stage than second. My humidity was staying around 52% and then when it went into second stage it would go down to like 45%. It just wasn't consistently comfortable. So I wired it where the fan runs at 50% in first stage by using the Y low terminal. I then turned the fan speed up to 450 CFM per ton. It works great now keeping the humidity below 50% most of the time in both stages.
This is unbelievably valuable information. Thank you for sharing it. I (as a nonprofessional layman) have been running off of intuition and thought this might be correct but having it spelled out to me step by step makes this so much easier to conceptualize. Thanks dude seriously, its something I've been struggling with for a while.
He's not just blowing air! Listen & Learn! Nice job Zack! 👍
I learned this as a teen when I tried to run a car with no thermostat which also served as a flow restriction. It was always overheating. It is all about matching the heat transfer capacity to the mass available for transfer (simplified college level thermodynamics). If the available mass moves to fast, it is difficult for the heat to be transferred efficiently because it needs more saturation time. Moving air slower is also cheaper.
Great video. I had a new unit installed with 18 speed fan. it was blowing WAY TOO HARD to the extent it was blowing water out of the pan. I brought the pro back out. He slowed the down and now it works very well, and the humidity is lower according to a gauge in my room.
Tech says i dont know what the CFM should be... then do the calc for CFM. IF YOU DONT KNOW THE CALCULATION........LEARN IT ! !
You can tell he knows what he’s talking bout! That’s one sage beard!
Don’t forget to email me about your prize
Sizing the equipment properly is the first and most important step. If the size is incorrect, everything else will be a compromise when it comes to cooling with moderate to high latent loads.
You can also set most electronic thermostats for a greater 'swing' which will cause the unit to run for a longer time then rest for a longer time. This gives the unit more time to dehumidify the air as well as cool the air.
too bad the smart guys on youtube are rarely reflected in the field and it's nearly impossible to find someone that will act like this without significant effort
All good things in life require effort. Most homeowners want ro take the path of least resistance, so they end up using the companies that are running commercials 24-7. Those companies tend to hire any warm body that can act as a technician.
Capitalism is all about profit and doing quality work takes time, which reduces profit. More than half of America's wealth is held by three men. Quality is of no real concern in this system.
@@ProleDaddygot to leave Babylon. COOHMP
Especially important on multi stage compressors. Lennox units almost always need to be dialed back.
If you have a matched system, the ahri rating should have a cfm associated with it. Also, it's critical that the system isn't oversized to begin with so it can run longer for better dehumidification.
I am turning down my fan speed to try to get more humidity out of the air. Thanks for the tip!
We live in Central Florida. Lately we have had 95+ degree days. Our humidity in the house has been throughout the day between 35-45% and dry. We recently changed from Merv 8 filters to Merv 11 filters. We just cleaned both coils with a coil cleaner and just changed our filter like we do once a month. We keep our thermostat at 82 and sometimes to 84 during the day and at night we put it down to 77. So far so good but the electric bill will be higher obviously. Great video on this subject. We are looking into Mr Cool or EG4 Mini Splits to put in in the near future in each bedroom and in our living room to help supplement the Central Air Conditioner or keep it completely OFF. That way we can just cook the rooms we want without keeping on the entire system.
Jeff -Sunny Central Florida ☀️
we are installing a EG4 hybrid with solar panels to be able to run it during the entire day using solar, supplementing the use of the central AC.
@@CL-en8nx Yes those are awesome 👍. We are looking into that one too. Awesome job. We would install their biggest one with panels in our living room
I live in C. Florida as well. How are you getting between 35% - 45% inside humidity?? I have a variable speed that runs constantly (as designed) and I can’t get below 50%. So I’m just wondering how are you getting it down to 35 - 45.
@@Steven_Falcon Depends a lot on your housing envelope. We've had 2 houses in Bradenton, FL.
The first one had a poor building envelope, and was generally 48-58% humidity downstairs and 50% to 68% upstairs. This was after upgrading to a multi-speed zoned system, as the stock single system couldn't even keep it cool upstairs on a hot FL day.
The current house is single story with far better attic ventilation and roof insulation, keeping the attic cooler, better windows, etc., even though they're not perfect. This home stays between 40% and 52% humidity. We recently added a multi-zone mini split to a couple rooms to supplement, and the humidity is even lower. Even when we had the rainy spell a few days ago, I never saw over 43% humidity on the central thermostat.
@@onecrazywheel Ha, ha, ha! Solar panels in the living room! :) (I really do know what you mean even though the sentence is structured incorrectly.)
Thanks Zac. Keep on keepin on 🤘🏼
CFM's drop when the homeowner installs a far more restrictive (aka allergen) air filter.
And when filters clog up over time, CFM's drop too.
And then there are homeowners that never change their air filters.
Of course people want that AC on the 2nd floor which most installations never get it to do properly.
Upstairs hot, downstairs cold scenario.
Those coils will dehumidify regardless of speed.
At coil temps increase the TXV also senses that and allow in more refrigerant.
If coil is still too hot after that then you have too small of a system.
Not the case at all with a vs ecm blower motor.
Man, That's True Talk and educational 👍
Almost missed this video. It's almost the end of the month!
I'm still puzzled that the HVAC gods decided CFM could mean either cubic feet/min or condenser fan motor. What happens when you order 1000 CFMs ?
you get crappy frigin more
Sad how many companies reward call backs, and eventually sales because the systems they touched become messed up especially when they are pushy Salesman with big muscle and clean white shirts
Hi Zack . Thank you for addressing this. My mother freaked out 2 winters ago when our 25 year old Trane furnace control module failed. I was not here and she had a Carrier infinity furnace installed. She had the evaporator coil and condensing unit replaced 5 years ago with American standard. It worked great and was very efficient. Since they are pretty much the same. After the carrier furnace was installed it is not as efficient. I believe its too much cfm for the coil. Only 15 degree differential . Should be 20 degree or better. I know there are several dip switches to change cfm. The guys who installed it said it's fine you have 10 degree subcooling. I have seen how to lower fan speed. Should I give it a try? I can't find any techs who know how to dial in a system. I'm pretty knowledgeable . What do you think. Thanks.
Give it a try. You can always put it back to current settings. I played around with my American Standard (Trane) 5 ton heat pump dip switches after reading the manual that explains the positions. I tried 350, 400 and 450 CFM settings. Filters also play a big role. I'm using low merv cheap filters for maximum air flow. My system is also designed for 10 degree subcooling.
Wow! What an eye-opener! I never thought about the air flow through the evap. You make total sense. Now, does this mainly apply to humid regions? Would the air flow make a big difference in an arid region like the southwest? Thanks!!!
Yes, in a dry environment, it is much less critical. In fact, in desert or arid environments CFM can be pushed up.
@@HVACShopTalk Thanks for the quick response! I was thinking the same for an arid region. But probably there is an optimum airflow in every situation. God Bless!!!!
would you say 50 degree coil can cause mold and bacterial growth?
depending on the seer rating
coils of 40-45 degrees are perfect 🥴
Tuning the CFM air flow can make a big difference in comfort and electrical consumption of HVAC.
Temp & humidity monitors are inexpensive these days. You can not only get the temp and relative humidity reading but the logging also shows the AC cycling time periods versus time of day. Verify humidity at several locations in house as it varies depending on any nearby heating sources like a TV or other equipment that puts out a little local heating. The localized heating will drive the nearby relative humidity lower and temp higher than house average.
During AC cycling periods in inactive state, the return grill area will likely dump some humid air back into room from wet evaporator coil in standby mode since evaporator coil is usually a bit higher than return grill.
On a single speed system, I always set minimum ON cycle setting in thermostat to at least 5 minutes of running time. Prefer to have a thermostat with adjustable temperature hysteresis control. You can better manage temp vs humidity and ON/OFF cycle time tradeoff by adjusting temp hysteresis setting in thermostat.
Excellent information to know! Thanks
I liked that.
Keep up the good work, Zack.
That's the upside mini split systems from known brands. It is already set up by the manufacturer.
I like to choose my ac mini split slightly too small as I still have a unit with ancient one stage technology. Doesn't cycle the compressor and gets more dehumidification done
Newer systems adjust airflow in real time based on humidity sensors.
It's a matter of perception. Personally I have lived with swamp coolers that saturate the air with moisture while providing high air flow at low temperatures and it feels great. Heat and humidity feel miserable. Cool and humid feels great. I would rather have high air flow with humidity and colder temperatures than to have lower air flow that is less humid with warmer temperatures. To each his own.
So you’re charging that 410 Bosch unit with R22?
Yes. I am bringing it back
@@HVACShopTalk
How do you find affordable R22?
Zach’s my brotha that’s a Bosch 2.0 why r u putting r22 on it 🤦🏽♂️
My ac runs about 15 min and off 7 min in the hottest part of the day (85 degrees, dewpoint 68). Does that seem right for a properly sized unit? (Thermostat set at 73, never sticky inside.)
I live in the desert so no humidity to start with
Great video
my brand new trane system coil compresor failed at 1 yr had changed but before it would turn of if i set it 76 it would turn on n off every 15 min running then 10 min off , know o set at 77 n never stops its cold n reaches but never stops i have to move the temp to 80 in order for it to turn on n off or else its would go on for hrs. Why could this be happening
Many reasons but something is obviously not right , call your installer and voice your complaint with them. An improper install, wrong condenser tonnage, or failure to insure correct blower speeds, incorrect operating pressures, super-heat or sub-cooling can all be issues. Have them send out their most experienced tech. Tranes are good units as long as they are setup and dialed in properly.
airflow, Airflow, AIRFLOW!
What if you increase condensor airflow?
Not good. the condenser air flow is typically specific to the size of the coil\system to remove the right amount of heat while keeping the head pressure correct for proper expansion valve operation. Keeping the condenser clean to reject the heat correctly is key. The temperature of the coil needs to be hot enough above ambient to properly reject the heat. Increasing airflow will decrease that temperature difference and not put you any further ahead.
ABC airflow before charge
The issue is he ran out of shaving razors😂
Enthalpy
How can you control the speed of the fan?
❤
This guy looks like he hasn't had a shower in 3 months
I take regular showers every week.