Commercial AC sizing


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Old 12-10-10, 10:48 AM
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Commercial AC sizing

I know this is not a real do-it-yourself question but I have to find an answer for the boss myself so I figure that would make it ok.

What is the formula for figuring AC requirement for a commerical building? The building in question is a 10,000sf "wing" attachent to the original building. The average height of the roof is 14' It is the typical metal construction with the standard wrap insulation. (I have no idea of the R value) There is one bay door that is only opened a few times per day for deliveries and the door has the weather boot around it to seal against the truck so there is not that much loss when the door is opened.
This is mainly a warehouse so there is no equipment creating or absorbing heat.
Any help on this would be greatly appreaciated.
 
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Old 12-10-10, 01:19 PM
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There are load cals that will need to be done on the building to find the heat load of the building. Just like residential u can't guess
 
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Old 12-11-10, 08:46 PM
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Thanks. Is there a place on the net to find these calculations?
 
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Old 12-11-10, 10:53 PM
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Don't think there is for commercial
 
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Old 12-12-10, 04:52 AM
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Exclamation It is grossly unfair of your boss to have given you this assignment!

I would assume that he would have you size this equipment and then attempt to act as his own contractor in purchasing and installing it.
There are charts for heat gain in commercial buildings readily available but I can not imagine someone without experience in this area being responsible for the costs of an installation this size.
The final decision on sizing has as much to do with previous knowledge as it does with calculations.

We really can't help you in a forum like this and would urge you to recommend your boss consult a mechanical engineer with expertise in this area.
 
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Old 12-12-10, 05:15 PM
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Thanks for the help guys.
The real problem is the building is now served with 4-12 ton units and one of them has bit the dust. The HVAC service company is trying to sell us an 8 ton unit he has on hand. The boss was just trying to make sure he didn't buy something that would not do the job.
I know this is not a forum for this type of question but I have always found help on here before so I figured I would not be let down this time.
Again, thanks for the help.
 
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Old 12-12-10, 05:25 PM
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I'd say no way! Over sizing equipment is not the norm! Usely they are under sized so I'd bet it will not work. But only way to no is to get a heat load done. I would be scared of a used equipment
 
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Old 12-13-10, 07:20 AM
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The unit is brand new, it is sitting in his warehouse collecting dust and he is willing to sell it a good bit cheaper than a 12 ton unit.
I found an online calculator that shows almost 250K BTU required. If that is the case then the 4-12 ton units are over kill.
 
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Old 12-13-10, 05:28 PM
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This dosent sound wright! If it had not been installed the manufacture should take it back!
 
 

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