How to slow down a Blaze King fan?

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aansorge

aansorge

Minister of Fire
Aug 12, 2011
967
Southern Minnesota
I generally run my Blaze KIng without the fan in the fall and spring but run the fans once it gets Minnesota cold. The fan speed adjuster seems to not allow a low setting....the lowest setting seems to be still pretty high (and a little loud). A lopi I had in the past had a rheostat that could bring the fan all the way down to nothing. I would like this on my Blaze King.

So is my fan adjuster out of whack?

Can I add a rheostat on the power cord?
 
Yes - keep the fan setting on high permanently and install the rheostat to control it.
Thanks for reminding me because my blower kit has a faulty adjuster also, I can get it to go on high with out fidgeting with the adjuster knob.
 
(broken link removed to http://www.ebay.com/itm/NEW-Plug-In-Fan-Speed-Controller-VS200-Fireplace-Blower-Control-Dial-A-Temp-SCP-/271020625538)
http://www.northlineexpress.com/dial-a-temp-rheostat-5005.html
(broken link removed to http://www.ebay.com/itm/Inline-Duct-Variable-Fan-Speed-Controller-Speed-Reducer-Vortex-Blower-Exhaust-/201389256230)
 
Thanks! I bought the one built in Minnesota.
 
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The rheostat also has a small white plastic screw. In order to see this screw you must remove the rheostat from the fan unit. This screw allows for low speed adjustment via impedence.
 
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Does anyone know if the Bucks have this Adjustment BKVP is talking about?? I don't like my Low either...
 
20 bucks gets you the plug in rheostat...
 
Sooooo, Leave the Stove Fan Controller on High and use these Motor speed controllers to Govern the fan speed???
 
No Harm doing that??
 
Nope. Works great.
 
Most inexpensive motor controllers don't work on resistance. They would have to be larger and with heat sinks to dissipate the heat. Instead most modern motor speed controllers work by high speed switching of the circuit. The motor is actually running in pulses with current only flowing to the motor part time.
 
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You are correct begreen. I suppose I need to keep in mind we were talking AC powered fans here. Excuse my over simplified explanation.
 
begreen said:
Most inexpensive motor controllers don't work on resistance. They would have to be larger and with heat sinks to dissipate the heat. Instead most modern motor speed controllers work by high speed switching of the circuit. The motor is actually running in pulses with current only flowing to the motor part time.
Click to expand...
You really impress me almost everyday, wealth of knowledge - good work my friend
 
Dad had a mechanical contracting firm. I learned a lot by osmosis.
 
saskwoodburner said:
I'm thinking of ordering one of these for my Englander 17. Do you notice any fan motor noise/hum with the controller turned down?
Click to expand...

A little bit. Just like with any motor and rheostat.
 
I got mine Friday. Is it okay to set that one at Half and use the one on the stove for fine tuning?? Or does the one on the stove need to be on high?? will it hurt if they are both at half?? Don't wont to smoke a Motor....
 
I think you only want to have one controller changing the voltage pulses to the motor. Leave the stove control on high.
 
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BKVP said:
The rheostat also has a small white plastic screw. In order to see this screw you must remove the rheostat from the fan unit. This screw allows for low speed adjustment via impedence.
Click to expand...
Thank you BKVP for this hint. I just adjusted mine after finding this low speed adjustment! Much appreciated!
 
davenorthshorema said:
Thank you BKVP for this hint. I just adjusted mine after finding this low speed adjustment! Much appreciated!
Click to expand...
You are welcome...Here comes the cold boys!
 
begreen said:
Most inexpensive motor controllers don't work on resistance. They would have to be larger and with heat sinks to dissipate the heat. Instead most modern motor speed controllers work by high speed switching of the circuit. The motor is actually running in pulses with current only flowing to the motor part time.
Click to expand...
Correct, for those that want to know more about how and why keep reading.... (I'm a nerd that loves knowledge of how things work and I also like to share that knowledge).

AC motors "want" to run as a single, constant speed based on the number of motor poles and frequency. For example, a 2 pole motor, on 60 hz runs at 3600 rpm (nominal). The same motor on 50 hz will run at 3000 rpm. Double the number of motor poles (4) and you halve the rpm.

Voltage put to the windings is what generates torque; I won't get too deeply into the theory, but motors want to run at a certain voltage, period. Decreasing that voltage will effectively slow the motor, but the electrical workings of the motor will still try to push the motor at the design rpm; running at lower voltage just increases the current draw (heat input) and you will overheat the motor and burn the insulation up over time. The motor would much rather run at full voltage and be switched on/off/on/off in rapid succession because the current draw (heat) will be lower. Another means of slowing a motor without burning it up is a variable frequency drive.

Switching power supply: rapidly turns the power on and off, which is hard on the motor, but not nearly as bad as running at low voltage. As the speed is slowed down the power decreases as well (the motor can't handle it). This works ok for low-load motors like fans.

Variable frequency drive: rectifies AC input power into DC, stores it on a DC Buss of capacitors, and an inverter recreates a sine-wave AC output at a frequency that can be changed by the user. With a properly rated motor you can decrease the frequency all the way down to 5 hz or so (~8% of normal) and maintain full torque without burning it up. The only problem at this low speed is cooling; properly designed motors for this have better cooling for low-rpm running.

That ends our basics of motor speed control lesson for today...
 
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