Duct Design Tips and Replacing Furnaces with Heat Pumps with Alex Meaney
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- čas přidán 1. 03. 2023
- We're back again with my HVAC design calculations trainer Alex Meaney (MeanHVAC.com), to talk about ductwork and connections and filters and how to get all this right when replacing an old system in existing homes.
Watch my first two videos with Alex:
Manual J Load Calculation • Manual J Deep Dive (an...
Manual S Equipment Selection • Manual S Deep Dive: Se...
Consult or train with Corbett: BuildingPerformanceWorkshop.com
Watch the first-ever TV series about the Science of Homes: HomeDiagnosis.tv
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Alex is such a cool dude. Met him and watched his talk at the symposium and he breaks things down to where most people can easily understand.
Alex is the Yoda of the HVAC world! Always great information from him.
Corbett, keep having guys like Alex Meany and Dustin Cole on your videos! wealth of info every time! Thanks for the content.
Excellent, thanks Luke!
Keep this stuff coming please. I love just listening to people who know they know what they're taking about and don't come off like they "think" they know what they're taking about.
Thanks as always Matt
The most important part you mentioned was right at the end about High seer units come at the expense of humidity control. I have seen many well known energy efficiency "experts" get that part totally backwards.
As far as humidity control from a high-SEER AC system, I have a sample size of 2 units. I have a Trane and Carrier unit, both with variable speed compressors and air handlers. The Trane unit does a much better job of hitting both humidity and temperature targets of 50% and 75F than the Carrier unit. The Carrier unit has a thermostat setting for humidity control, which allows it to run longer and reduce the temperature by up to 3 degrees. It just makes that part of the house cold and clammy. It's a one story house in the DFW area, the Trane unit cools the bedroom/bathroom area of the house, while the Carrier does everything else. I've heard the reason is that the Trane can run its compressor at a significantly lower capacity than the Carrier can, but I'm not the expert.
I would also expect that HVAC manufacturers do not set up their units to dehumidify when testing SEER, as unless humidity control is part of the test, their results will be not as good if they are using energy to dehumidify after the temperature target is met. Whether standalone dehumidifiers would be more efficient than running a large compressor/air handler at low speed is yet another interesting question.
I’m excited for the amount of knowledge I’m going to learn from this video
I love Alex! He's my spirit animal ❤️
Great video from two Rockstars!
I read an article on existing homes that Alex wrote last year. He said for a load calculations on retrofit homes, a visual inspection could be done rather than a blower door to measure infiltration.
Do you think infiltration can be measured with a visual inspection?
(I posted the same comment with a link to the article Alex wrote, but I think CZcams removed the comment because of the link)
I'm going to do a follow up on that article soon. I would say that it's not my opinion that a visual inspection can "measure" infiltration, but rather "estimate" infiltration to sort homes into two camps: the "this house doesn't appear to be so leaky that the likely results of a blower door will impact my equipment size compared to my estimate" camp, and the "I definitely need a blower door test" camp.
Ok, I’ll jump in here as someone who’s done hundreds of blower door tests and say I’m continually surprised by test readings- homes that might look leaky are sometimes tight, and vice versa. Anyone with 1 day of training can come along with a blower door and prove the load calc wrong, so I’d never leave it to guessing.
Great info
Usually tho a high seer rating accompanies full scroll inverter and variable speed technology so while ratio of latent removal lower coil Will be able to cycle less and this more absolute humidity removal right?
With a move to higher-end filtration, does it make sense to add an axial flow fan in situations where the pressure drop on the return side becomes a challenge for an existing system?
Another great video guys. Question, I have read the ACCA low load home manual, I know super nerd here, and read the recommendations about increasing velocity by reducing duct size in the last 10 feet of a branch, as well as using nozzles versus standard registers and grilles. This is suppose to to help with air entrainment and mixing, specifically for a low load home. The problem is the manual doesn’t provide any math formulas to use in order to check the impact on a low velocity duct system, nor does it recommend or provide a listing for product manufacturers. I have reached out to a number of suppliers who look at me like I am crazy. 1. What are your thoughts on the LHH recommendations, 2. What are your thoughts on the impact to static pressure and friction loss following such recommendations, 3. Any products or manufacturers you would recommend for high throw nozzles, etc? Thanks
The Rick Ruben of HVAC
On the nose
Why does high efficiency come at the cost of dehumidification ? I purchased a 2 stage 17 seer ac thinking it would be better at dehumidifying but it basically does not make any difference. Ive actually noticed during anlong run time it goes up.
With some of these newer units, it seems the poor dehumidification has to do with using larger evap coils that take a longer time to get cold enough to start condensing moisture out, and them not getting as cold.
So , ceteris parabis, am I better off with one large return close to the blower , or two with larger overall opening surface area but this longer overall return duct runs.? If I add another branch return to current return duct, a, I always going to get improved performance ? Can you have too much return? Too many returns ?
Don’t think there’s any downside to oversized return except time and money
First! Thank you for the video!
You win and you’re welcome
Hi Corbett, I enjoyed the video! Can you pick a piece of HVAC equipment (manufacturer/brand/model) and give us an example showing the different results you’d get between using the AHRI data on the equipment label and the “hidden data” available to contractors? Also, can you tell us what to ask a contractor in order to either get the “proper” information yourself or to be sure that the contractor knows it exists and how to get it and use it in their calculations?
Stay tuned Ryan
I like knowing how many watts it takes to cool a watt (COP) (season/days), and in the case of a heat pump, how many watts to heat a watt, so i can compare that to various alterative energy sources. I think SEER sort of obviates that number. For example, NG used to be 10 to 15x cheaper than electricity (per therm of heat), now it varies widely but it is closer to 4x, so heat pumps start looking good, especially with solar.
You guys know your stuff! Please keep producing great and valuable content. I had a few questions. Can you spray foam part of a HVAC rectangular trunk (about 8' long) that is flush against a wall so it'll be difficult to insulate with traditional means. Where it's located is in the attic over a sunroom and its registers are located upstairs. They produce low air flow and do not get that hot or that cold.
Problem is that it sounds like you won’t be able to insulate the wall part of the trunk. Heat follows the path of least resistance.
The next question is, as I mentioned a few, days ago my blower door test for my old 1960's home was so bad at 15.6 ACH so we have a comfort issue in certain rooms, mainly upstairs. I'm looking at getting Aeroseal to come in 3 weeks. Do you think that's the right way to go. What I've done so far was insulate my attic and air sealed it as well as sealed the attic Hatch. Thanks
@@HomePerformance I understand. I was think maybe the wall insulation is helping on that side.
Do you mean Aerobarrier? I wouldn’t seal the ductwork until I knew how leaky it was, and what the static pressures and airflow through it was.
@@HomePerformanceyes, OK.
Hi HVAC Pro Community, hoping to get some feedback from you, I have an 18 year old home with two furnace/coil attached HVAC units in my attic, (California). The contractor did a terrible job with the ducting design so I have way too much pressure output on the two bedrooms directly below the furnace and too little pressure output on the bedrooms on the other side of the house as the supply plenum distribution box is on that side and feeds two bedrooms, 2 baths and the master bed closet, plus its suspended up in the air almost touching the ceiling 2x4s and the box gets extremely hot in the summer--my plan is to 1) shorten the supply run to this box so the box sits right in the middle of the house, and then attach all ducting for all bedrooms from this one location, and 2) I plan dropping the box to the attic ground level, ensure its sealed, then encase in additional insulation and add insulation to the attic on top, do you think this will equalize the output pressure on the registers at all 4 bedrooms? I know theres a lot more info needed to provide exact predicted results, but based on what I plan to do, does this seem like it will achieve my desired results, thanks in advance
In years past, many standard heat pump AHU's made nominal CFM at 0.4" TESP. SEER2 dictates systems get rated at 0.5" TESP. This should even the playing field so manfacturers will stop putting weanie blowers in AHU's.
Are probes absolutely necessary when using a nanometer to measure static pressure? I'm asking because most units come without probes, that are affordable for the homeowner that wants to check it out.
Yeah, if you just stick a pressure hose into an airflow you’ll be seeing TOTAL pressure, which may be higher or lower than the actual static pressure. Static pressure probes are totally necessary.
@@HomePerformance Thanks for answering my question, thing is probes seem to be 3 times the cost of a manometer, like $100 bucks each!
No way- shop at Trutech Tools, should be $20 tops:
trutechtools.com
Also, a good manometer like the DG-8 costs $600
@@HomePerformance The DG-8 isn't a good manometer. It's a GREAT manometer!
It's so frustrating that these companies aren't more transparent with there data.
If your home only has 1 return air duct and grill it's a major red flag!! Most homes will need 2 returns. Find an HVAC contractor to test the static pressure, it's so dang important!! I test every home and so many need a 2nd return air duct and grill for proper airflow.
KP, keep up the good work. My system was designed for one return and built and tested by me, video posted several years ago. Anything is possible if you plan and test correctly.
@@HomePerformance I've watched your ductwork videos and I show homeowners your static pressure video darn near every day. The problem is on a standard built home it's a 14" or 16" flex line return. That's what fits through a standard stud bay and isn't large enough for a system that is 3 ton or larger. I wish we could get builders and inspectors to test statistic pressure!! At least half of the system replacement we do need a 2nd return air duct and grill.
Nice to hear, KP! Agreed, assuming everybody knows what they’re doing AND actually do it right every time is a total joke.
Cost of heat pump/electricity in cold climates like Maine?