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Old 11-07-2012, 01:22 PM   #16
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Originally Posted by Technow View Post
That is correct.

Estimated a house yesterday: currently has 1.5tons up and 2.0 tons down. Load calc was 1.5tons down and 2.0 tons up. manual d showed duct going to Room over garage was too small (hence the complaints)
But your manual j NOT the final answer. The next guy will find it completely backwards. It happens all the time, no two manual j's ever come out exactly the same.

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Old 11-07-2012, 01:45 PM   #17
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But your manual j NOT the final answer. The next guy will find it completely backwards. It happens all the time, no two manual j's ever come out exactly the same.

The "next guy" is wrong.

If you don't know how to do one properly you can just replace whats there or do 500 sqft/ton and it will COOL or listen to the homeowner who wants a 4 ton instead of a 3 ton when a 2 ton will work.

humidity control takes correct sizing.... Maybe there is a reason they call it "Air Conditioning" and not "Air Temperature Control"
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Old 11-07-2012, 01:52 PM   #18
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Go read hvactalk.com. You'll see many professionals not coming up with the same answer. Be it how they perceive information may be different or what they plug in but it's never the same. I doubt you will EVER find two manual j's ever coming out the exact same.
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Old 11-07-2012, 01:56 PM   #19
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It's just that you got there first and the home owner doesn't know any better, doesn't realize there are far too many variables which people see differently so yes, if every single variable is input the exact same than it'd come out the same but that's never the case.
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Old 11-07-2012, 02:04 PM   #20
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Bull......

If you do ANY calculation correctly it is also subject to a margin of error from measurement differences and calculation rounding.

And then you have to figure in the "Idiot factor"....Never been trained how to do one and never checks insulation values, just like everything else in this industry there are guys that know what they are doing and guys that fake what they know and never learn anything and guys who are clueless.

Like the guy who learned it from him, who learned it from him, who learned it from him.....but if you go down the line the first guy was wrong.

DONT GIVE ME ANY THUMBRULE: SHOW ME WHERE ITS WRITTEN!

And YES...I am one of those guys on HVAC-Talk.
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Old 11-07-2012, 02:42 PM   #21
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I've seen it too many times, even on here, homeowners come on and have three different contractors give three completely different results and recommendations for system sizes.

I'd be willing to bet that take yourself and let's just say BT for example, to the same house and let you all perform a heat load that the result will be different. Using the same software but your own input.

I know BT knows what he's doing, yourself I'm not so sure about.

In other words take two very highly skilled professionals and it''ll come out different.
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Old 11-07-2012, 02:51 PM   #22
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I think our calcs would be very close within the margin of error. BT actually seems to know the physics.

You never hear him say "he has been doing this for xx years and I know what I am doing"
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Old 11-07-2012, 03:02 PM   #23
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It's all relative to how someone sees something, the information that's plugged in. That's it.

And since no two people are alike there always seems to be differences. RoboTec, I'd bet his are really different. He specializes in envelope applications.
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Old 11-07-2012, 03:05 PM   #24
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Anybody can do all the manual J tests etc but shade trees or lack of, house orientation, glass area, whether they close drapes, windchill values etc play a huge part of how we size equipment and actually knowing what works seperates the "real world" Pros from the theorists.
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Old 11-07-2012, 03:13 PM   #25
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Bull......

If you do ANY calculation correctly it is also subject to a margin of error from measurement differences and calculation rounding.

And then you have to figure in the "Idiot factor"..:
That is the idiot factor.
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Old 11-07-2012, 03:16 PM   #26
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Anybody can do all the manual J tests etc but shade trees or lack of, house orientation, glass area, whether they close drapes, windchill values etc play a huge part of how we size equipment and actually knowing what works seperates the "real world" Pros from the theorists.
and these are some of the variables that factor into the idiot factor factoring the last factor.
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Old 11-07-2012, 03:30 PM   #27
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That is the idiot factor.

No its basic physics and since it seems you lack any formal education and do not understand about margins of error and its affect on calculations. I guess we better end this discussion.
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Old 11-07-2012, 03:34 PM   #28
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That's it. Your word is gold. All hail Technow, the only hvac technician in the world.

I wasn't being insulting to you, I was stating a simple fact and that fact is never do you come across two manual j's being the same.
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Old 11-07-2012, 03:35 PM   #29
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I would not accept your word in my home and that's with HVAC college and 12 years in the trade. Not yours alone.
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Old 11-07-2012, 03:47 PM   #30
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I would not accept your word in my home and that's with HVAC college and 12 years in the trade. Not yours alone.

But I know more than you.....I've got 27 years in the trade ..... so.....

"I've been doin' this 27 years"........ I guess I must have learned everything from a guys who didn't know what they were doing.

I could give a crap if you think my words are lies, I am not coming for Thanksgiving

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