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Join Date: Jul 2013
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How To Calculate Motor Capacity Using Only Fan Capacity

07/10/2013 12:49 PM

Dear All

I am new to this forum. Due to some issues with my company's fan supplier, my consultant and i are unable to find the motor capacity of fan. We do not even have the datasheet of fan.

Fan has already been supplied at site and is required for cassette filter in coal handling plant in a 12 MW Thermal Power Plant based in Asansol, West Bengal.We need to place order on motor and hence require the motor capacity

We only know the fan capacity as 2500 to 3000 m3/ Hr.

Can anyone please suggest me any way to calculate the motor capacity as i have to place order accordingly.

Thanks & Regards

Rising Sun

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#1

Re: How To Calculate Motor Capacity Using Only Fan Capacity

07/10/2013 1:27 PM

Actually the "fan capacity" takes into account a lot of things which you did not include in your description. You may begin to understand the issues if you check out this calculator/conversion site where you can change things and see some of the effects.

You need to realize that there are no "standard ducts" for which a given capacity can be referenced. And you haven't mentioned anything like the RPM needed.

The volumn of air says nothing about the size of the duct, speed of the air, and other important considerations such as variable speed control or thermometer type On/Off cycling.

Lastly, it would be best to look at the label on the existing motor. If you can't easily get to it, you can approximate it closely by reading at the voltage and current measurements used to operate the existing motor. Other important considerations or parameters include things like motor cooling options and many other details that affects the cost of the motor. If you choose a cheaper motor than the one you have, you will reap the rewards of an uneducated guess. Even if you get everything else right, your replacement may not fit because it has a different (bolt hole) mounting pattern. If nothing else, get a motor vendor to pay you a visit. It pays to have good vendor contacts so you can get reasonably good answers.

And don't forget to look at the diameter of the motor shaft. Many times, the same power rating is available with different shaft sizes.

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#2

Re: How To Calculate Motor Capacity Using Only Fan Capacity

07/10/2013 1:27 PM

Did you look on the motor nameplate?

Contact the supplier of the fan for specifics on the motor? Surly they have a web site. look at it. Find your fan there and look at the specifications.

You found this site, so you know how to search.

Look at other fans on the internet and compare outputs and motor sizes.

What is your function? Do you work for the power plant, or are you a consultant, too?

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#4
In reply to #2

Re: How To Calculate Motor Capacity Using Only Fan Capacity

07/10/2013 1:45 PM

Thank you for the prompt reply.

Actually i work in the head office of a power company whic has a thermal power plant. I am not consultant.

We have no previuos installed motors at site. Cassette filter fan for the first time will be installed and commissioned.

The vendor name is Uptech India. The person from our office who has placed order has left the office and vendor is not responding us. we are not getting any details on any website.

Only cassette filter with fan capacity 3000 m3/hr has been supplied and my consultant and i are clueless about it.

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#5
In reply to #4

Re: How To Calculate Motor Capacity Using Only Fan Capacity

07/10/2013 2:06 PM

You really need brand name, model number or at least a schematic diagram with critical measurements to identify motor size and mounting frame configuration, as well as electrical requirements, and any safety requirements....

http://www.nederman.com/products/baghouse-dust-collectors/pulse-jet-cleaning/fmk-modular-cassette-dust-collector

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#6
In reply to #4

Re: How To Calculate Motor Capacity Using Only Fan Capacity

07/10/2013 2:40 PM

If you're clueless, and you can see the fan, think how clueless we are, with absolutely no information to go on.

Which Uptech India? No address? no contact information?

Sounds like you're wanting someone to spec your fan for you.

Good luck.

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#8
In reply to #4

Re: How To Calculate Motor Capacity Using Only Fan Capacity

07/10/2013 4:06 PM

seeing as how you're up Chit creek, have a paddle on me

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#13
In reply to #4

Re: How To Calculate Motor Capacity Using Only Fan Capacity

07/11/2013 4:11 AM

Contact the Managing Director of the company supplying the fan and suggest that if the technical team of that company will not respond same day to this simple request, the purchase order will be withdrawn. That usually cascades a result!

Bluff is a valuable business skill. Use it!

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#3

Re: How To Calculate Motor Capacity Using Only Fan Capacity

07/10/2013 1:42 PM
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#7

Re: How To Calculate Motor Capacity Using Only Fan Capacity

07/10/2013 2:46 PM

What's the Static Pressure the 2500 To 3000 m3/hr was spec to? Fan is also a broad term for many devices that move air. A window exhaust fan with 18" blade 1/4 hp motor at 1725 rpm will move 2500 cfm(4200m3/hr) @ 0.000 SP.

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#9

Re: How To Calculate Motor Capacity Using Only Fan Capacity

07/10/2013 5:35 PM

Choose another fan supplier.

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#10

Re: How To Calculate Motor Capacity Using Only Fan Capacity

07/10/2013 7:54 PM

Pay the fan supplier, they may be a bit more receptive then.

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#11

Re: How To Calculate Motor Capacity Using Only Fan Capacity

07/11/2013 12:31 AM

Did you contact motor manufacturer?.

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#12

Re: How To Calculate Motor Capacity Using Only Fan Capacity

07/11/2013 1:38 AM

hello,

try to look at the manual of the dust collector, so that you can find the static pressure needed for the dust collector system to perform efficiently. also, try to measure the actual diameter of the impeller, blade configuration and look for its performance curve on the internet.

in that way you can find the most possible motor capacity. it worked on me every time.

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#14

Re: How To Calculate Motor Capacity Using Only Fan Capacity

07/11/2013 6:18 AM

If unsure, don't use the product. Get another supplier that can provide you with all the necessary data, backup service and an actual proper product. Unless sufficient data can be obtained, just scrap the items and treat them as faulty parts so that accounting can properly write them off. I can't understand the rationale behind your operations. Is it company policy to save a couple of bucks and jeopardise the safety and integrity of their million or billion dollar investment. If yes, then you company is run by a bunch of cheapskates.

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#15

Re: How To Calculate Motor Capacity Using Only Fan Capacity

07/11/2013 6:21 AM

This Flowchart will help to explore idea. Knowledge is vast and it can be explained through any form in my life I had try to find some new thing because working at Mactec - electrical contractor is valuable not because he works for us but due to his or her achievements we get the point of light to throw away the darkness.

Let take the example-
Motor - 120v & I=13amps
120V X 13A = 1,560 watts
Let 20 amp circuit
20A X 120V = 2,400 watts

2,400 watts X 80% = 1,920 watts of safe capacity

Nice information is shared.

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Users who posted comments:

Danielciara (1); Fredski (1); lyn (2); NotUrOrdinaryJoe (1); ozhero88 (1); ozzb (1); pnaban (1); PWSlack (2); rising sun (1); Russian_1979 (1); SolarEagle (2); TonyS (1)

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