Would Like to Upgrade My 135Cfm Blower. Is It Possible?

Vinmaker · Post by **Vinmaker** » Tue. Dec. 13, 2011 2:33 pm

Ok. So I have spent some time on the Grainger site and gave thought to the flange reducers I need to create. In designing my sheet metal folding template, it occurred to me that I may be creating a "leaf blower" effect with the reducer. I now am scared that I could be making a small hurricane (with all the stove dust included) thru the unit.

As I said. I currently have a 135cfm unit. It is stock and presumably designed for the specific stove and not put on to save some money with a smaller unit. A large 555 CFM unit might be too big. As a man, bigger & more powerful is always viewed as preferable. But now I am questioning such testosterone infused wisdom. I am thinking that I might be better off going to a 273 CFM unit. A unit that is very close to the unit on my former Russo stove.

555 CFM Flange opening is 5 1/4 x 4 1/4.
273 CFM Flange opening is 4 1/8 x 3 5/8.

The Current 135 CFM unit is 2 1/2 x 2 1/2.

Any thoughts out there on my hurricane theory? Do you think I am trying to push too much air thru the unit?

Thanks,

Vin.

jpete · Post by **jpete** » Tue. Dec. 13, 2011 4:37 pm

You have to remember that the faster you move the air, the more you cool it off.

Bigger is not always better.

I think jamming all that air through the passageway designed for 135cfm will only create back pressure which will force the fan to work harder. There is probably a law of diministhing returns situation here but you'd need much more knowledge that I have to pin point it.

McGiever · Post by **McGiever** » Tue. Dec. 13, 2011 10:06 pm

There also existed the ability to vary whatever size blower's speed by way of a rheostat/controller.

Vinmaker · Post by **Vinmaker** » Wed. Dec. 14, 2011 7:47 am

McGiever wrote:There also existed the ability to vary whatever size blower's speed by way of a rheostat/controller.

I had that on my previous stove. It almost looked like a dimming switch that you plugged the blower into. Then plug the unit into the outlet. It has a dial that you could turn to vary the speed. I did not that many of the motors said not for use with a speed controller. I figured that is what they meant my it.

However. My understanding of electric motors is that a big benefit of them is the ability to slow them down my limiting the electricity that they get. And I did not think it harmed the motor at all. Isn't that how commercial trains work? They just throttle them based on electricity going to the motor?

Vin.

McGiever · Post by **McGiever** » Wed. Dec. 14, 2011 11:04 am

Here is what I reported in a previous thread:

McGiever wrote:I have put some thought into this concept as well.

Even did a little experimenting as to switching from one speed over to the other speed.
My experiment lead me in the direction of changing between speeds w/ an relay.
Because w/ the Speed Controller and full power on same circuit (parallel)...full power will always prevail, and no reduced fan speed will result.
The relay would remove full power when reduced speed is called for.

I would recommend a Solid State Motor Speed Control...aka A Better Light Dimmer.
I have a KB Electronics model...it has features that you will not find in a dimmer.
I especially like the integral trim pot to adjust the minimum motor speed on these.
If you ever would go too low w/ a light dimmer you could end up burning out the motor.
ETA: Shaded Pole, Permanent Split Capacitor (PSC)...My comb. fan is a PSC type, it stated that NOT for speed control, but w/ minimum speed set w/ trimpot there is no problem...controller said it will work on PSC, and I have done it for many days.

Here's some info and a link to site...don't forget ebay either...Search: Motor speed control "Greenheck" or "KB Electronics"

http://www.kbelectronics.com/Fan_Speed_Controls_T ... ntrols.htm

KB's 21 Wall Mount, AC Motor Fan Controls are packaged for Distributors. They are designed for mounting into a 2" X 4" electrical wall box. They operate from 115/230/277VAC, 50/60 Hz and have a maximum rating from 2.5 - 20 Amps at ambient from 25° to 40ºC. They provide infinitely variable speed motor control for Shaded Pole, Permanent Split Capacitor and Universal (AC/DC) motors. The variable speed motor control contains an on/off line switch, a high gain RFI noise suppression filter, an adjustable trimpot to set the minimum speed and a flame retardant ABS enclosure. Applications include Ceiling Fans, Commercial Vent Hoods, Industrial Blowers, Laminar Flow Hoods, Heat Tunnels and Magnetic Stirrers.

jpete · Post by **jpete** » Wed. Dec. 14, 2011 11:26 am

Vinmaker wrote:
McGiever wrote:There also existed the ability to vary whatever size blower's speed by way of a rheostat/controller.
I had that on my previous stove. It almost looked like a dimming switch that you plugged the blower into. Then plug the unit into the outlet. It has a dial that you could turn to vary the speed. I did not that many of the motors said not for use with a speed controller. I figured that is what they meant my it.

However. My understanding of electric motors is that a big benefit of them is the ability to slow them down my limiting the electricity that they get. And I did not think it harmed the motor at all. Isn't that how commercial trains work? They just throttle them based on electricity going to the motor?

Vin.

Trains are DC though. I don't know all that much about DC, but there is a difference. Unless an AC motor is designed to be variable speed, running them under voltage is harmful.

National Electric Code calls for no more than 3% voltage drop from the panel to any electric appliance. I only know that because my final exam was yesterday.

Vinmaker · Post by **Vinmaker** » Wed. Dec. 14, 2011 7:39 pm

running them under voltage is harmful.

Yes. You might be right. I'll have to rethink this.