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Can anybody please explain the following?
1-What are the major difference between fan and blower?
2-Why blowers used in the fan coil and air-handling units instead of fan?


Thanks in advance.
Ashok.

Here's my take... others can elucidate more...

First, the term fan and blower are often used interchangeably and to many people the terms are synonymous. Often it is more of a regional preference, much like engine or motor when referring to an internal combustion engine.

That said, by definition, a fan is just the air-moving device. It is attached to a shaft that is turned by a motor (usually electrical, but could be a gasoline engine in the case of swamp boats used in the Everglades or leaf blowers, for example). Fans are as varied as cars...there are axial-bladed fans like the ceiling fan in your house or a window fan. Axial fans usually move large volumes of air at low pressure. Then there are centrifugal fans, of which there are 3 major classes---forwardly curved, backwardly curved or straight-bladed. They generally move less air but at a higher pressure. Some fans are called compressors if they turn at sufficient speed to materially compress the air they are moving. Centrifugal fans are usually mounted in a housing that looks like a snail shell. The inlet is in the center and the discharge is the opening of the shell at the outer edge of the scroll. When the fan is integrated with a housing and a motor, it then becomes a blower, much like you would find in a Grainger catalog. Blowers are usually small centrifugal fans. A blower is the complete assembly of the fan, the housing to direct the air, and the drive motor. Because blower housings contain and direct the air to where it is needed, this is why they are used in more applications than an open fan blade. Each fan type has its own characteristics, which dictate the choice for a particular application. Entire books are written on fan engineering. Hope this helps.

Bruce Axtell

Generally blowers are more effective at higher pressures and fans at lower pressures. This is why blowers are typically used in duct distribution methods. Fans are also quite sensitive to the amount of free air around them as the outside edge does the most work. Fan venturis or surrounds are important to the flow and adapting them to rectangular duct work requires larger plenums.

Regards

cww

There is no technical distinction between a blower and a fan!

Regards,
Phil Corso, PE
Boca Raton, FL
[tal-2@webtv.net] (Epsiconinc@aol.com) {pcorso@itt-tech.edu}

Actually their is major diff. between fan & blower. The blower has more pressure diff. than fan (i.e. 1.1-1.2)

Blower is one kind of a fan. Just they have added names to them. So you have a suction fan, blower fan, Cooling fan depending on the application.

Any device that has more than a fan blade for the purpose of moving air or any gas is a Fan.

my 2 cents
Sekar

Hi Ashok,

The "2003 ASHRAE HVAC Applications" book does not list blowers in the index at all but has a load of entries for fan whilst the "2001 ASHRAE Fundamentals" book entry is: Blowers. See Fans and then has long list of entries for fans.

I'd suggest a blower is a colloquial term for certain types of fans so all blowers are fans but not all fans are blowers.

In Australia at least, the HVAC engineers I work with all refer AHUs and FCUs having fans and seldom if ever call them blowers.

To get a relevant answer for your location you'd probably be best to talk to a local supplier and ask them for their definition.

Regards

Peter Whalley
Magenta Communications Pty Ltd
Melbourne, VIC, Australia
e-mail: peter*no-spam*@magentacomm.com.au
delete *no-spam* before sending

Years ago when I was working at a "Blower" manufacturer our rule was based on specific speed (for centrifugal & axial flow devices). So basically if the device put up relatively higher pressure and lower flow it was called a blower. Conversely, higher flow and lower pressure was a
fan.

John Catch
http://www.inflowinc.com

...And if you hooked it up backwards, it was a vacuum pump, right? ;)

Rufus

Fans, blowers and compressors are differentiated by the method used to move the air, and by the system pressure they must operate against. As per American Society of Mechanical Engineers (ASME) the specific ratio - the ratio of the discharge pressure over the suction pressure – is used for defining the fans, blowers and compressors.

Equipment    /Specific Ratio   /Pressure rise (mmWg)
Fans         /Up to 1.11              /1136
Blowers      /1.11 to 1.20        /1136 – 2066
Compressors  /more than 1.20           /–