Author	[Modern View]
Kerwin 02-28-2013 09:47:26 204.54.36.245 Report to Moderator	Does anyone know if it is possible to vary the speed of a wall ventilation fan? Found a wall vent fan that I'd like to use for a poultry shed, where variable speed would be ideal. 20 inch fan with a 1/3 HP motor. It appears to be single speed as setup, but wondering if a variable switch could be possible. [Reply]   [No Email]
missouri massey man 03-01-2013 11:58:53 108.90.234.133 Report to Moderator	Re: Variable Speed Fan Question in reply to Kerwin, 02-28-2013 09:47:26   Quoting Removed, click Modern View to see Does the "mushroom" fan you are planning on using have a gray metal oval capacitor (or gray plastic oval) attached to the side of the motor? Or is it a belt drive motor with the same style capacitor?? If so, these motor will be what is called a "Permanent Split Capacitor" (PSC) motor and can be varied in speed with nothing more that a wall mount rheostat or speed controller. Check WWGrainger to locate. These motors do not have a centrifugal switch nor do they have a start winding that is required to be removed from the circuit. The gray oval "run" capacitor stays in the circuit continuously and limits the amount of current through the start winding after start-up. The fact that a capacitor is on the motor reflects that it is a single phase motor, but if it were in fact a three phase motor, it could be run safely on single phase by powering it with a vfd and will allow it to operate at infinite rpm from 0 to the maximum rpm rating of the motor. If it has a black plastic (bakelite) round (tubular) capacitor, that would indicate a "capacitor start" motor and would have a centrifugal switch internally. These types of Greenheck, Carnes, etc aluminum mushroom ventilators when set up for single phase have the PSC motors, whether belt drive or direct drive. Hopefully this is helpful info, not too boring and not too long of a reply...... [Reply]  [No Email]
Bob 03-01-2013 10:03:00 64.255.159.192 Report to Moderator	Re: Variable Speed Fan Question in reply to Kerwin, 02-28-2013 09:47:26   NO need to attempt to "re-invent the wheel" and mix and match your own fan and speed controller.There ALL SORTS of choices for variable speed or thermostatically speed controlled vent fans for livestock buildings. Local hog confinement barns near here have them as well as a friend"s turkey barns, for example. Don"t know the brand names, offhand, but GOOGLING "Variable speed confinement building fan" will get you started. There's some educational resource links at the end of the .pdf linked below. http://learningstore.uwex.edu/Assets/pdfs/A3784-06.pdf MORE info: http://www.munters.com/upload/Related%20product%20files/controls-5000seriesliterature.pdf This post was edited by Bob at 10:07:46 03/01/13 3 times. [Reply]  [No Email]
Tramway Guy 02-28-2013 14:22:16 24.92.254.197 Report to Moderator	Re: Variable Speed Fan Question in reply to Kerwin, 02-28-2013 09:47:26   Use a three-phase motor, using a VFD...the VFD will run on single phase in. Just have to size the VFD a little larger than normal for the size of motor. [Reply]  [No Email]
David G 02-28-2013 11:45:52 205.215.206.18 Report to Moderator	Re: Variable Speed Fan Question in reply to Kerwin, 02-28-2013 09:47:26   I am going to stand corrected, it is not practical to use a VFD on a single phase motor with a capacitor start. The VFD does not like seeing the capacitors during starting. [Reply]  [No Email]
Bill in IL 02-28-2013 11:43:57 132.3.49.80 Report to Moderator	Re: Variable Speed Fan Question in reply to Kerwin, 02-28-2013 09:47:26   My guess without knowing what type of motor you have on the fan is no it cannot be speed regulated. You need to have a 3 phase motor to use the VFD. Therefore no start circuit in the motor just 3 windings one for each phase to create the "rotating" magnetic field. The VFD would create a variable frequency output to control they syncronous speed of the motor. What about repowering it with a motor for a furnace blower? Many of those are multi speed. [Reply]  [No Email]
Dean 02-28-2013 10:19:38 24.1.134.162 Report to Moderator	Re: Variable Speed Fan Question in reply to Kerwin, 02-28-2013 09:47:26   The fan is no doubt driven by an induction motor. You must use a VFD to operate an induction motor at variable speed. Dean [Reply]  [No Email]
David G 02-28-2013 09:55:28 205.215.206.18 Report to Moderator	Re: Variable Speed Fan Question in reply to Kerwin, 02-28-2013 09:47:26   A VFD would be a good application for that. [Reply]  [No Email]
JMOR 02-28-2013 10:22:42 72.181.173.171 Report to Moderator	Re: Variable Speed Fan Question in reply to David G, 02-28-2013 09:55:28   Quoting Removed, click Modern View to seeOK, a question for you. Induction motor with a start winding switched out once it comes up to speed. You feed it with the VFD and set speed low enough the the start winding is still switched in by the centrifugal switch. How will this motor do in this situation? I'm reasonably sure that smoke is in the answer. [Reply]  [No Email]
David G 02-28-2013 10:27:45 205.215.206.18 Report to Moderator	Re: Variable Speed Fan Question in reply to JMOR, 02-28-2013 10:22:42   Just hook the VFD to the motor, it will take care of providing current and voltage to start it. It varies the frequency, voltage and current. [Reply]  [No Email]
David G 02-28-2013 10:29:10 205.215.206.18 Report to Moderator	Re: Variable Speed Fan Question in reply to David G, 02-28-2013 10:27:45   In response to the start windings, will have to check. I believe you take the start windings out of the circuit. [Reply]  [No Email]
JMOR 02-28-2013 10:56:44 72.181.173.171 Report to Moderator	Re: Variable Speed Fan Question in reply to David G, 02-28-2013 10:29:10   Quoting Removed, click Modern View to seeUnless I'm badly mistaken, I do not believe you can start a single phase motor with one winding. [Reply]  [No Email]
David G 02-28-2013 11:16:54 205.215.206.18 Report to Moderator	Re: Variable Speed Fan Question in reply to JMOR, 02-28-2013 10:56:44   We have stumped the district engineer, it is headed for Milwaukee now. [Reply]  [No Email]
David G 02-28-2013 11:06:27 205.215.206.18 Report to Moderator	Re: Variable Speed Fan Question in reply to JMOR, 02-28-2013 10:56:44   I have an email into Allen Bradley on how to do that, will post when I get a result. [Reply]  [No Email]
JMOR 02-28-2013 09:53:03 72.181.173.171 Report to Moderator	Re: Variable Speed Fan Question in reply to Kerwin, 02-28-2013 09:47:26   Quoting Removed, click Modern View to seeIt depends on motor type. 1/3 is a bit on the large size for a universal motor, which can be slowed, but could be one that size, but unlikely. Some other type can be slowed, but others will simply burn up when operated on low voltage. How is it started? Centrifugal switch, capacitor, ?,?,? Answer is probably not. [Reply]  [No Email]