2024 AHR HVAC Show: Testing, Mini-Splits, and Why Manual J is Pissing Me Off 

It is so frustrating to me to after watching this channel and learning a lot to find so many design flaws in so many newer buildings I go to (it’s obvious the calcs. Are wrong) one building didn’t calculate for cold air return through the bathroom doors and there having two outside walls, the lobby has a huge cold are return so all the heat stays in the lobby and the bathrooms are freezing. And to make matters worse the registers in the bathrooms are near the door no where near the outside walls! Woman wont even use the last stall! We might have to put a heated seat in there😂

Alex Meaney brought up a wonderful comment about thermal mass and the exterior of buildings; especially in climate zones with large temp swings. Very interesting to think about brick or block vs wood or vinyl. Alex is all ways dropping little nuggets of wisdom that are simple in concept but deep. I really admire that guy. I could watch a 12hr stream of your wonderings, they're great. Also very interested in the Trueloads software. I am also struggling with the current software options and their dated calculations and difficulty with adding things like ERV's and makeup air.

My new Mitsubishi heat pump kept up with -5 degrees weather(ave.) for about 5 days here in Wisconsin also but it raised my power bill by over $150 for the month! It’s the highest power usage that my home has experienced in the 16 years that we have lived here. Also Alex Meaney made a ton of sense! I wish I had talked with him before I made my HVAC purchase.

That tool that looks for sound was pretty cool. Its crazy how useful even a reasonably priced thermal camera that plugged into my phone was when we were building out house.

I am so glad go see mini splits with proper filters rather than rock catchers 👏👏

I have a former coworker who built a "geothermal air heat pump system". He came into possession through an auction hundreds of feet of very very large black pipe and metal corrugated pipe. He has it configured with two seperate air supply pipes(winter/summer) and a switch box next to the heat pump. He has a garage/barn with a large but low attic space. He packed it full of black plastic pipe. He runs air through an external filter that is a screen and a series of dust baffles and the air flow thru the pipe and out and down to the corrugated pipe buried 7 or 8 feet down. The metal pipe zig zags and then pops up next to his heat pump into switch box where heat pump pulls its air from. During the summer he has another longer metal pipe buried a little deeper that pops up in the same swtich box. And he switches back in forth. He added a solar fan so that during the summer the winter pipe continues to pull in hit air to try and warm up the soil.

Always a treat when we get a peak inside Alex's great nerd brain!

Those acoustic imagers are amazing. As a side note: chewing when talking with someone looks really weird. :)

After tracking runtimes on projects where I did the Man J and the install, you really see how much Man J oversizes heating. There’s a bit of oversizing in cooling too but not near as bad as heating.

Great info, thanks for sharing.

Adaptive control is not AI, neither is zoned control for hydronics. We keep our bedrooms a t 67F and baths at 72F - simple with hydronics. Time to up the game

Our MultiZone Mitsubishi heat pump unit is definitely holding us down in central North Carolina. Coldest night this year was 14*F and the system didn't even blink. I did see it short cycle and freeze up once but I think it was a miscommunication with our Ecobee relays. Let the coil defrost and was back in business.

I thought houses only lasted for a couple hundred years until I stayed at the Anchor Hotel in Saalfeld, Germany. The structure was built in 1486 and is still standing today.

Hey Corbett - Good content but it raises a concern I have had for some time now. You have advocated for performing an accurate Manual J and making sure that the person doing the Manual J calculations is fully qualified. When you hire a consultant, you trust that they have the appropriate knowledge and experience in their field. That should include a full understanding of how the software acts upon the user provided input. Based on your discussion with Alex Meaney, do you believe that the Manual J software is incorrect? If so, how would you approach that discussion with a former, or even a new client? My Project is at the stage where a load calc needs to be done soon and I am wondering what to do…

I love Alex Meaney. The man is an endless well of knowledge. Did you happen to check out the METUS booth? I'm trying to figure out when their new hyper heat sumo minisplits (MUZ-FW or is it FZ?) are coming out.

Just a few thoughts on the discussion about load calculations. First, it should take into account all the types of heat transfer, conduction, convection, and radiation. That means you need to know or assume all the relevant properties like specific heat capacity, density, emissivity, etc; even material structure matters; closed cell materials like high-density spray foam or EPS/XPS will always have an advantage in regards to convection over a fibrous material like Rockwool, or fiberglass. In fact, fibrous materials can have declining convection performance as the thickness increases. Second, you should look at the system dynamically. Hour by hour, at the very least. Modern computers are more than powerful enough to simulate a full year of heat transfer in a few minutes. You might not have the budget or time to do a full 3D FEA heat transfer and airflow analysis on every building, but I think doing a dynamic 1D simulation of a full year should be the standard, not just a one-point spot calculation like manual J. In my ideal world, the heat load simulation should output a model of the building that can output the exact room-by-room load at any possible combination of indoor and outdoor conditions. That model should then be fed into the building controls so that it can modulate all the equipment as needed to meet whatever conditions exist at the moment. We have been doing this type of model-based control in other industries like aerospace or chemical processing for decades at this point; there's really no reason it couldn't be done for HVAC.

We just built a small 985 SF 2 bedroom cabin in the PNW. The building is framed, roofed and sided and we are planning on a 3 zone mini split system. One for the main part of the home and one in each bedroom. The smallest head unit available for the bedrooms seems to be 4000 BTU's. How will this affect the air conditioning side since the units are oversized for the space?

I hope that the future hold more controls like the one you showed that can adjust the system to be more flexible, then we might not have to assume so many calculations and get it wrong. The controls can take care of it and make up for human error. Well its a dream anyway

Near the end they talked about thermal mass. It made me think about the human thermal mass an heatstroke on day 3. If where you sleep is above 95 degrees then your body is gaining 0.5 to 2 degrees of extra body temperature each day that it can’t get rid of. So on day 3 when you wake up your body can be at 100 degrees still. That causes a huge risk of heatstroke on day 3 that was not there on day 1 and 2.

will be interesting to see if your parents house can cool during design temperature day. If it does then it is a msicalculation in manual J or more input than recorded. If it doesnt then it was higher latent load.

I looked up that TPI Ultravision. 25,000.00 out the door. No thanks.

Just a thought couldn’t they make the drain pans with a layer of copper in it to mitigate the bacterial growth? My wife said she has an idea that will only cost you pennies. Actually put pennies in the pan😂

I ducted my heat pump water heater from and back to the crawlspace of our home. This way we are cooling and dehumidifying the crawlspace anytime it’s running. Our crawlspace is not yet enclosed.

Awesome vid ty

what about Geo thermo

Do like to share this video please.

Appreciation for the video and insights. But getting rid of the gum in your mouth when filming so closely would make these more palatable

Non-engineers attempting to do engineering.....