Can anyone suggest an online manual J course please. There are so many of them and I can't tell which is good or not.
Thank you in advance

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It depends on your goal. 

If it is to start generating designs quickly using one of the Manual J softwares, then it is best to take the software manufacturers classes and read their manuals and just jump into the software with small straightforward homes.

If yiou are looking to be certified then ACCA offers 5-year certification class at

Manual J takes time to learn and real life experience is the best way to supplement any formal training.  It is important to undersatand both Manual J, S & D theory AND the HVAC design software thoroughly and this simply takes time and doing projects.

Good luck!

Thank you Tracy
I am a rater, I was hoping to learn the calculation for sizing the equipments
Thanks again

WOW what is your back ground?   I have been teaching ACCA MJ for 30 years and each class is for skill that should be used in work.   Most HVAC schools will have heat gain heat loss class.  I just did a heat loss - code class for building inspectors  over half said the HVAC contractors should do this not the code person.   I do loads each day and most just look at sqare foot of area.  

Hello Eric
I am a rater, I was hoping to learn how to size the HVAC for a house
Thank you so much

A Resnet HERS index rater will give a size and will preload ACCA MJ wright   Then will have to adjust peaple load and about 11 other things.   But a if you per load name, wall/attic size R/U window size, door size, solar input on south and west,  the hard stuff is done.   I ran a lot of loads from HERS.  

start with the base:  

Principles of Heat Transfer
• Heat energy cannot be destroyed.

• Heat always flows from high temp to low temp

Conduction through a Shaded Wall
Q = U X A X T
U – Overall heat transfer coefficient of the surface  or 1/R
A – Area of the surface
T – Dry bulb temperature difference across the surface

at this point 1/2 the class or group is asleep  and with each math assessment more start to snore.   So the keep the eyes open  we must add photo's and grafts so the non "word" learners have a way,  Give 4 ways to learn each part of the course.

Factors Affecting Human Comfort

Dry-bulb temperature
• Humidity
• Air movement
• Fresh air
• Clean air
• Noise level
• Adequate lighting
• Proper furniture and work surfaces  -  show how high mass can "suck" the heat out of skin.

So now what do you what to do?  Learn more about insulating or math to do the Heat loss and gain?

I'd recommend this one (link below). It covers the fundamentals as well as the use of software. If you scroll to the bottom of the page, you'll see a YouTube video that'll tell you a little about the course structure.
Thank you Isaac

Be sure the size that you ACCURATELY calculate actually gets installed. Often contractors pretend to do load calcs that "just happen" to come out to whatever the standard sizing is for the area. If you're getting about 500sqft per ton for every house you calculate, you're doing it wrong.

Thanks Bob

Bob, raters are typically doing new homes. You want to adjust this number?

If you're getting about 500sqft per ton for every house you calculate, you're doing it wrong.

At what number do you think he should start being concerned?

Unless the builder did a really crappy job with the house or it has an unusual load, 750sqft per ton should be the MINIMUM. Yet in our area 600sqft per ton is typical for new construction. Meanwhile houses that were built in the 1970s are getting the typical 500sqft per ton. Yeah, only 20% difference between brand new construction and 1970s house. Manj is clearly being fudged...


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