HVAC Fail: Mechanical Plan Red Flags, and How to Find Them in Your Man J/S/D Design
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- Опубликовано: 2 апр 2023
- It's easy to go wrong with residential HVAC designs- here are a few explorations of mechanical plans that have obvious red flags.
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Great Explanation and video as always Corbett !!!
Glad you liked it!
Gosh! I have a lot to learn about these HVAC systems.....I hope this is a good start to look at over and over again to learn. Here up here in Atlantic Canada, on Prince Edward Island, calls for ERV unit. I do not plan to have air conditioning .... because the code up here says we have to have Poly on interior on studs....the solution to prevent mold in the cavity, with R 30 exterior insulation, is to use Smart Membrain by Certaineed. Thanks for all this!☺👍💯 🙏🇨🇦
So, in my home office, there's going to be at least one 19" rack of computer equipment, plus UPS battery backup, lots of networking and computer gear, etc.... So, if that was my home office, there would be plenty of load being generated even if I'm not in the room.
Yeah my equipment all generates a lot of heat too, but nowhere near requiring 4 dedicated cooling appliances. I would be much more concerned about recycling the heat out of that room. However you can get some great over locking results by hooking up a commercial air conditioner to your CPU 😄
Great channel and info! Can you, on an upcoming video, or deeper dive on specs, share how to calculate/verify a dehumidifiers effectiveness? or a calc app / formula that indicates out put performance?
Thanks Kevin! This should make you happy:
Dehumidifiers How/What/Why: Installation and Testing of Ultra-Aire 120H and MD33
ruclips.net/video/aaiq7QzfW2g/видео.html
Hey Corbett, I love the content you have on here. I sent you an email last week about my future home design and how I plan to build my envelope for the home. I was wondering if you would be able to help me figure if the way I’m insulating the building is overkill? If the systems I’m wanting to use are right? I’m still 3 years or more away from actually building this house but I wanted to try and build it the most efficient and effective way that I can.
Sounds great, Mac, I'm sorry to say I'm drowning in emails, will hope to get to yours asap, but if you'd like to book a consult here's the link: buildingperformanceworkshop.com/video-consulting
The commercial software gave it away. There may not be any actual kickbacks going on but the commercial construction game is very you scratch my back I’ll scratch yours. All those mini splits, all that duct work. That’s somebody scratching a mechanical contractor’s back.
… & why all the mini-splits with a new build like this?
@@smitm108 mini splits are sold as giving people total control over their indoor environment. And also, that’s how commercial buildings are usually designed and built, with short duct systems to to three or four rooms. A mini split installs a lot like a hot/cold water fan coil so a commercial designer would be more familiar with laying out the floor plan that way.
Seems like the home owner was smart and is going to Corbett for a second opinion.
Yes! Normal people are starting to look at these things and recognize red flags!
10:30 oh lord you should see some of the nightmares in NYC apartments. I'd *kill* to have 49 CFM in our walk in closet. It gets so damn hot. FLIR revealed to be some kind of space in the wall that gets fairly hot - 80-90°f on the surface of the wall. I suspect it's actually a electrical chase carrying the main service wires for a few dozen apartments or at least something like it.
Hi Corbin, @ around the 16:49 mark you mention that because the dehumidifier wouldn't be able to pull 70pints per day because realistically the air doesn't contain sufficient humidity, you recommend up sizing the dehumidifier. Can you elaborate on why? If there is less humidity, wouldn't it mean that you could get away with a smaller unit? Or does this mean that a smaller unit would have to work harder than a larger, to remove the same volume of moisture? I'm in the market for a whole house dehumidifier, and am not sure what size to install. You'll have to forgive my ignorance, it's why I ask.
Happy to elaborate, watch this:
How to Size a Humidifier or Dehumidifier for Any Home (HVAC Training, Nuance Edition)
ruclips.net/video/mQTCl8c3Plw/видео.html
4:35 I mean, given the wild and absolutely uncontrolled spread of literal SARS, yeah, some of the time in those hot summers and cold winters I'm gonna have windows wide open when people are around
So Corbett what if u have a large master centrally master closet with no windows or exterior walls door code much of the time first that room need appreciable ventilation even with little thermal load?
Sorry John, not following you exactly, but I think this might help: rooms with no load but circulation need can get a small ERV exhaust, one that will at least cycle the air 1x/hour (room volume / 60)
@@HomePerformance 👍🏻
@Home Performance If you can afford a 14000+ square foot home, surely you can afford a central chiller plant and boiler. That, along with thermal storage and a modulating distribution system is about as comfortable and luxurious as it gets. Plus, the boiler gives you hot water, and accessory heat for things like snow melt, pool heating, greenhouses, etc.
I cannot afford that, I’m sorry. But my client could I suppose.
@@HomePerformance I mean, if they were planning on putting in 40 TONS of capacity?... If your client has that sized budget, and their main priority is luxury and comfort in any possible situation, you might as well do the thing properly. It would probably save them some money, over putting in 19 separate systems.
I’m just jokin around. They do not need 40 tons at all. More like 7.
@@HomePerformance They may only need 7 tons for design day conditions, but if you know it's going to be a party house, it's nice to have that boost capacity if they can afford it. There are no downsides apart from the cost if you have dedicated dehumidification and modulating or buffered capacity. It's like horsepower in a car; if you can control it, having more horsepower is always nicer than having less.
Except inverter heat pumps only disl down to 30% of max, so if they installed 40 tons, they’d have a 13 ton single stage system, basically.
Why go through all that work drawing it out? An it actually does look like wrightsoft like the way the registers and ductwork looks so just WHY? Lol
Corbett- where did your house end up on that metric between 1200-2500 sq feet per ton?
John, using my living space sq ft, it’s 1204 sf/ton, but because I have 47,000 cubic ft of volume, Man J calls what we have 5875 sq ft, in which case it’s 2350 sf/ton.
Very insightful about their lazy "manual j" and how over powered what they specified is.
I do have to disagree about not putting cooling in the home office though. A high end gaming computer can easily put out 500 watts or 1800 BTU while in use. Even triple screens can add up to 100 watts (350 BTU). It makes sense to add at least some cooling capacity to a home office. I'd be installing a mini-split if I didn't have cooling. Overheating rooms is a very common complaint by gamers. I do agree that if it's just a laptop it's not needed.
In the build I'm planning I'll have up to 3000 watts (10,000 BTU) of computer equipment heat in the basement (I'm a nerd, but hey, that's also why I'm learning about HVAC!). In the winter I can let that heat up the stairwell to help heat the house. In the summer that would cook a small high performance home (30,000 cu ft). I could try ventilating the room to outdoors, but humidity control in winter would be a major problem. I may just install another mini-split.
Hey Mark, thanks for the comment as always, but don't forget the Man J is specifically targeting the ONE HOUR that's hottest in the year. If all the cooking equipment, the laundry, AND the computer equipment will all be running at 5pm on the hottest day of the year, then OK I agree. But Man J has a lot of fat built into it already, so I'd be cautious about adding the equipment load just because it's there- the schedule of its use would also be important to consider.
@@HomePerformance The computer equipment I have is running 24/7, participating in distributed computing projects. It's a very constant 2500 to 3000 watts at the moment (it adds about 2 MWh to my monthly bill). With the snowy season coming to an end I'll be powering a lot of it down over the coming weeks as I don't have sufficient cooling in my current place (I rent). I may still do the same during heatwaves in the new place.
Cool, you know what you’re doing. A lot of people add equip load without thinking of the schedule in July/Aug, but sounds like that’s not you.
@@HomePerformance The majority of what I've learned is from this channel! It's thanks to your excellent videos.
Aw shucks man
Lower the fan speed to 1750 CFM and get rid of the dehumidifier.
What about days when it's 70 deg F and raining, but the ERV keeps on dumping outdoor air inside? That's basically what we need the dehus for- when the A/C will not turn on at all.
Houses that have humidity problem is not when it 70 degree and raining and the AC is off. It when its 82 and humid outside, AC is short cycling because it's oversized and can't remove the humidity out of the house. That's when you see register sweating and mold growing on the drywall around the registers. From experience Whole house dehumidifier are too small to remove humidity out of a house. That and they use a lot of electricity. Total waste of money in my opinion. A proper sized AC should run at a minimum 20 minutes when its 82 outdoor to maintain the house under 55% RH.
High performance homes are fundamentally different, RVB- they pipe in outdoor air continuously, so yes the problem is 70 degree rainy weather. You won’t really feel it til you live in one, but just wanted to warn in case you ever work on one.
@@HomePerformance i've designed and install hvac system for net zero house and 1 off-grid house here in Dallas, all of them are geothermal heat pump. None of them have a dehumidifier
Good luck is all I can say
Alec doesn't explicitly state it in his video posted earlier today, but I can feel him channeling Corbett in emphasizing Manual J and testing.
ruclips.net/video/DTsQjiPlksA/видео.html
More education is a great thing!
I'm sure the rest of this design is a mess, but if they have a rich-person gaming computer in that home office room (13900KS + 4090), that's easily 600-800W (peak loads up to 1200W) of heat (~2K to 2.7K BTU/hr) while playing games. and if there's anyone who's gonna sit around playing video games all day...
Haha good point but I’d want the client to have informed them of something like that, which they didn’t.
@@HomePerformance "yes, this room will be for...my dance group practice...we might get...sweaty, and also, can you make sure the registers won't be blocked by the custom daybeds for this room? The interior designer should have the layout"
Need a dehumidifier in that sweat lodge STAT
I believe it’s extremely dishonest of you to post content like this at @2:46 you are taking about no need for cooling and complaining about the side of the diffusers. The side of the diffuser is to reduce noise, the second diffuser based on what I see is the fresh air component and is brought in at a neutral temp. The return is just that necessary return. Think of 1200 watts worth of equipment put two people in that space and that fully justifies the cooling load. This is truly shameful of you to drum up work by criticizing others.
Manual J spells out how to build in default internal loads. People who just add 1200 watts to whatever room they feel like are the problem.
@@HomePerformance Manual J is not the only approved method of calculation, especially for a home this size, most jurisdictions will allow other equivalent methods of calculation. From NYS website “Calculations shall be in accordance with ACCA Standard 183-2007 for commercial, ACCA Manual J for residential, or other approved calculation methods in accordance with the Clean Heat Program Manual.” Internal equipment loads should be accounted for please refer to some ASHRAE documentation.