Need of Help

[harsen]

Hello,
As i wellknown in the forum by asking repeated question on ducting now i have another one,
I am working in the ac contracting company in a gulf country , now i am quoting for the new project for the installation of ducts , normally when the consultant give the design drawing they decide the duct size accordingly we calculate the ducting squrarefoot and we quote,

In a current project they are not giving the duct size , so Is there any formula to find out the duct area by knowing the machine capacity (Ton , CFM)

May be its a silly question plz give a solution

Senthil Kumar

[Brian_UK]

You need to decide whether you want a high velocity or low velocity system and design your ductwork and fans accordingly.

[harsen]

If its a low velocity system?/////

[TRASH101]

hello Harsen

the clues are in the units

i.e. you know the volume m3/sec
then decide your velocity m/3
A quick division gives you m2 i.e the cross sectional area of your ductwork.

If it is a small system you wont have to modify the basics other than allow a percentage for losses.

Be sure that the fan is capable of the design volume against the resistance of your ductwork.

[Sridhar1312]

Senthil kumar
Better to go through CARRIER Susytem design manual, even then when you are quoting you need to estiamte based on the duct routing velocity etc.
For commercial building you may take velocity of 1500 feet per minute and decide. There is lot to it.

[glenn1340]

Hi Harsen,
Try this link:

www.vent-axia.com/knowledge/handbook/section2/simpleducted.asp (http://www.vent-axia.com/knowledge/handbook/section2/simpleducted.asp)

Hope it helps.

Glenn

[harsen]

Hi Harsen,
Try this link:

www.vent-axia.com/knowledge/handbook/section2/simpleducted.asp (http://www.vent-axia.com/knowledge/handbook/section2/simpleducted.asp)

Hope it helps.

Glenn

Glenn

Thanks for the link its really useful

[Peter_1]

It's only useful in small system.
Don't tell you weren't warned.
Brian_UK gave you the first question to start with.

[Magoo]

Spin it back to the consultant Engineer, he is not doing his job, and will roast you if it does not work. He is either lazy or incompetent. My reaction would be , don't get envolved if not confident to design the system. Or else offer a design option and charge the consultant for costs incurred.
magoo

[BobTheBull]

You got that one right, magoo. Don't even think about bidding until the ME gives you all the duct information. Trust me on this one, you do well to look suspiciously on this job from the start. Always bid on the specs you are given, and that only and make that clear in your quote. If you don't you will probably get burned. Since the ME turned very deficient plans, I suspect if you do get this job there will be nothing but trouble and you will be sorry you got into it. This is based on long experience. If you do get the information be sure to bid high so that if you get the job you will have enough money in it to deal with all the changes I'm bettin' you're goin' to see.

On the other hand, cudos to you for looking for the study material to educate yourself. By all means learn all you can. Just keep it to yourself in regards to the ME. Magoo is right, he will roast you at the first opportunity.