HVAC Sizing. Formulas, Rule of Thumb, or Heat Load Calculations

In this video, Joshua Griffin goes over the misinformation in the HVAC industry on HVAC sizing when it comes to websites saying you can use a rule of thumb or formula. Josh goes over why these can cause issues and why you should have a professional perform a proper heat load calculation when sizing your next heating and air conditioning system. Finally, he wraps up by going through several of the things covered in a proper heat load calculation.
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---------Chapters-----------
0:00 Intro: HVAC Sizing
0:49 Get a head load calculation
1:51 Formulas or Rule of Thumbs
2:41 Home size
3:42 Location and climate
4:44 Insulation
5:04 Home types and other factors
5:23 Software and other considerations
5:38 Solar heat gain
5:54 Humans and appliances create heat
6:37 Outro
#hvac #heatload #hvactips

[@michaelcinaz]

Proper sizing of an air conditioner, gas furnace, coil box, refrigerant lines, return air ducts, air filters, and supply air ducts are critical. Have the new HVAC system tested after it’s installed. Have it checked for static pressures (return, supply, total), proper airflow per room, and proper temperature. 👍

[@robertlong7723]

All of the factors that you mention certainly contribute to heat and cooling loads. These factors combine many variables into the calculation of a single load factor. Wouldn't the best indicator for a replacement HVAC be evaluating how well your existing heating and cooling units have performed and how often each one cycles at various outdoor temperatures? Then use that information in conjunction with the size of the current units to decide if capacity of the replacement units need to be larger or smaller.

[@Ivan-qq6dj]

Thankfully for sharing

[@Garth2011]

We have never heard of any HVAC folks doing a heat load calculation prior to installing a new system or replacing an existing system. They all seem to be fine with replacing the hardware with the same capacity that is existing and for new construction they always choose the cheap "contractor" models with cheap low grade ducting, supply and return vents. In the southwest, Type of roofing material might also have some play into the heat calcs as lots of folks use "spanish tile" materials that remain hot long after the sun goes down continuing to radiate heat.

[@redsadventures5654]

I worked for a company that did the basic load calc for every install but it definitely wasn’t a “real” load calc. They advertised that it was. I no longer work for that company

[@bloomqmx]

Does it make sense to upsize the coil compared to the compressor. ie 2.5 ton compressor and a 3 ton coil. Thx

[@shericantor1031]

I’m in Richmond - can you put a link to your Load Calc Contractor?

[@NewHVACGuide]

He’s old school. No link. Call us and we will get you the info. Thanks

[@noahfigueroa3534]

Any insight on how to read/understand a heat/cool analysis? I had to pay $200 for my analysis but there is a ton of information on there. I just need to know what size mini split to install. I am a licensed general engineering contractor that installs my own mini-spits but then I hire a local licensed hvac guy to inspect and charge the system.

[@bigytv8392]

Nobody argues validity of properly sizing the HVAC system. However, in your video you throw in a lot of terms just to fill the space and mostly confuse people without offering much help. Basically, lots of words and not much advice, except do it. It's not rocket science. Plenty of online resources to figure out how to do manual J calculation accounting the factors you mentioned. Anyone with basic technical education who wants to do it should be able to get it pretty close. All useful info in your video can be easily summed up in 1 min.

[@bobboscarato1313]

Three minutes is more reasonable!

[@alberthartl8885]

This is not rocket science. Furnaces are typically 48, 60, 80 or 100 000 btu. Ac are 24, 36, 48, or 60 000 btu. If you are doing a heat pump, size to the heating load. Humidity will tweak the number up or down a 1/2 ton. Don't oversize or you will short cycle. That pretty much sums it up. (30 year general contractor)