Is it possible to dial down inline fans?

[TheTimeKeeper]

+1 to a variac.. I built my own controller, with a high temp controller so if temp goes over a set temp, it bypasses the variac to give 100% fan speed! I did learn the hard way and fry 1 variac but got it all sorted in he end... see here! -> http://www.uk420.com/boards/index.php?showtopic=262664&st=30&gopid=2717123&#entry2717123

 

[chimei]

Variac is NOT the proper method to control inline fans with Permanent Split-Phase Capacitor motors (Vortex, Canfan, Fantech etc). The ONLY reason a variac works to control fan speed is the voltage drop causes the motor to lose torque. The motor will then try to compensate by pulling more current, in turn possibly burning out the fan motor windings.

In motors such as P.S.C. type, you MUST use a Diac fired Triac type speed controller (such as the KB Electronics one previously mentioned) to prevent the current from rising and posssibly damaging the motor windings

Also Note: The Can Max fans have a DIFFERENT type of motor than the centrifugal type inline fans

Sorry to bump an old thread but I am really confused on Variac's and inline fans. I was using the speedster type controllers for years with the darn hum and then found many people referencing these variac controllers. So I bought a couple and found they work well in dialing down the speed with no hum at all.

I don't want to burn down my house though, but the only text I can find against this is from your posts imnotcrazy.

First, one article I found, states that these vendors use Shaded Pole Motors:

-Vortex
-Can-Fan
-Valueline
-Elicent
-Active Air

Which your text says is OK to use a Variac.

Your text named some of these specific vendors as NOT being ok to use Variac because they use Permanent-Split Capacitor based motors, with my research so far only these types of fans use this type of motors:

-Dayton squirrel cage blowers (Generally PSC motors, but they also make a shaded pole version)
-S&P Mix-Vent TD line
-Grainger squirrel cage fans

imnotcrazy, above says: the proper method to control inline fans with Permanent Split-Phase Capacitor motors (Vortex, Canfan, Fantech etc).

I called Vortex fans and they said a variable voltage transformer is fine for lowering speed to their fans. (I assume they meant variac) the person I spoke with did not know that by name., and on Can's website they even say in one of their FAQ's:

"requires the Can-Trol Speed control. This control provides absolutely no motor hum when controlling the fan, it also gives you the option to control the voltage entering your fan, with an easy to use dial you can go from 1v to 130V with a turn of your hand, no matter what voltage you run, your fan will not hum! "

They don't say Variac, but that is what they are referring to I assume. -- I looked and it is a variac : https://4hydroponics.com/can-trol-variable-speed-controller

So can anyone comment on any of this? I understand that iamnotcrazy is trying to help us all out here, but there seems to be conflicting information.

Can anyone confirm that Vortex uses Shaded Pole Motors? Specially the S-line model?

Edit:

Well I am even more confused now, I found a link on Vortexes website that says in their FAQ that they do use brushless permanent split capacitor motors.

So I don't understand why Vortex themselves would tell me a variable voltage transformer is ok to control the speed to one of their fans.

 

[chimei]

OK so I did some tests. I am not seeing at all what iamnotcrazy said should happen I believe..

He said above: "The ONLY reason a variac works to control fan speed is the voltage drop causes the motor to lose torque. The motor will then try to compensate by pulling more current"

My results showed otherwise, and the triac was actually not consistent in its current usage.

iamnotcrazy, if you could please comment.

I took a kilowatt meter that has voltage/watt/current capabilities.

I first started by measuring the Vortex S-line 6" connected to the Kilowatt connected directly to power.

.79 amps on start-up of the Vortex. (startup spike)
It then took like 3-5 seconds to stabilize down and stay steady at:
.62 amps

I then took my Variac 3 Amp rated and hooked the Variac to house power and connected the Killowatt meter to the Variac output and the Fan to the Kilowatt meter.


I set the Variac to 75 volts output.

On power on of variac the fan wen to .50 amps and stayed there, no variation.

I then quickly raised the Variac to 110 volts, and the fan amp usage went to .59 amps, no variation up or down.

I then quickly lowered it back down to 75 volts and the Kilowatt measured .50 amps, no spikes, it went directly down to .50 amps usage when I quickly lowered the voltage back down to 75 volts.

I then took the variac and raised it to 110 and back down to 75 over and over again and it always went up in current slightly and then back down to .50 amps usage, I NEVER saw a spike in current usage from the Vortex fan.

I then took a Speedster Triac based speed controller.

The speedster connected to house power and the kilowatt meter connected to the Speedster and the Vortex connected to the kilowatt meter.

I set the speedster to just below high speed on the edge of medium.

When I turned everything on after plugging in the speedster the current usage readings kept fluctuating for as long as I did this test.

It would go between .58 amps and .87 amps usage, (.58, then .75, then .60, then .87, etc.. ) and that annoying buzz in the background was present.

No matter what speed on set the Speedster to it would act this way where the current would change over a range and NOT stay steady.

The ONLY way I could get the triac Speedster to register a constant current usage was by turning it all the way to max high.

 

[rives]

Some motors are incompatible with triac-based speed controllers and will not work on them except at full speed. Triac controllers work by limiting the portion of the sine wave that is made available to the motor, and will not work well with motors that have capacitors because the capacitor tries to negate the effect of the triac.

A variac is a variable transformer and it functions by reducing the voltage. Anytime the voltage to a motor is reduced, the current goes up if the load remains constant. The reason that you are seeing the current drop when you reduce the voltage is because the load is dropping simultaneously with the voltage. In an industrial setting, for maximum motor life circuits are designed so that the motor will not see a voltage drop in excess of 3%. Variacs will work on inline fans because of two things - 1) the motor is hung in the airstream, so the reduction in cooling isn't as much of an issue as it would be with an open motor, and 2) the airflow (load) created by the fan drops off very quickly as the motor speed drops, so the current drops off more quickly from the load reduction than it can increase from the reduced voltage being applied.

You need to be careful not to get the variac turned down so low that the motor can't restart if the power goes off momentarily. It's easy to get into this situation because the fan will run fine if started at full power and then is slowed down to a minimum setting. However, you can get the setting so low that the motor won't have enough starting torque to break the friction loose and get the fan moving from a dead stop.

 

[Jhhnn]

^^^

Rives is right on the money, as usual. Any inline AC motor fan sold as speed adjustable will work with either a triac or variac speed controller. Triac controllers create a deformed voltage waveform & therefore motor hum. Variacs create a smooth output waveform of lower amplitude (voltage) & no hum.

It's quite possible to create electronic speed controllers that produce no motor hum but nobody wants to pay for them.

Some of the new fans (hyperfan, for one) actually have electronic brushless DC motors & integrated speed controllers. They are *not* suitable for use with speed controllers other than those furnished with the unit.

Variacs are less efficient than triac speed controllers & therefore require some airflow for cooling. That's why retail variacs have vented housings. Incurable DIY'ers (that's me) can find naked industrial variacs on ebay, mount them in suitable enclosures but it's scarcely worth the trouble vs pre-wired retail units.

 

[stoned-trout]

all my fans are on speed controls .. one was made up by a friend one was a 300watt fan speed control...both work fine..yeehaw.. both plug and play

 

[chimei]

Thanks for the information guys, so is imnotcrazy wrong?

He stated:

In motors such as P.S.C. type, you MUST use a Diac fired Triac type speed controller (such as the KB Electronics one previously mentioned) to prevent the current from rising and posssibly damaging the motor windings

According to Vortex, the fan I tested (s-line fan) with the variac is a PSC type motor, and I did not ever experience an increase in current usage when going down quickly from a higher voltage.

At first I started out worried about the variac, but now after my tests it does seem that the speedster control (triac) puts much more strain on a PSC type motor (when set to anything lower than 95%) then the variac did.

I am just trying to limit any possibility of a fire introduced by an error on my part.

It would seem as long as I keep the variacs separate from my grow area as much as possible (run an extenstion cable for the fan to the variac) and give the variac some space on non flammable surfaces, if a variac does malfunction it would be isolated. And confirm that the variac voltage that is set, that the fan is capable of spinning up from a complete stop.

The variacs I am using are the ones from amazon and ebay.

The fan controller I tested with my Vortex s-line that had allot of current usage variation was this one:

 

[Jhhnn]

Rives explained it well. Amps x volts = watts, also expressed as work. With speed controllable AC fan motors, the amount of work falls off with the voltage, so current will not rise.

We really don't need to think about it too hard. If the maker says an AC fan is speed controllable then either triac or variac controllers will work. They even work on S&P mixed flow fans, high or low speed.

 

[chimei]

Rives explained it well. Amps x volts = watts, also expressed as work. With speed controllable AC fan motors, the amount of work falls off with the voltage, so current will not rise.

We really don't need to think about it too hard. If the maker says an AC fan is speed controllable then either triac or variac controllers will work. They even work on S&P mixed flow fans, high or low speed.

OK thanks, I have just been focused on that one statement that imnotcrazy said:

Variac is NOT the proper method to control inline fans with Permanent Split-Phase Capacitor motors (Vortex, Canfan, Fantech etc). The ONLY reason a variac works to control fan speed is the voltage drop causes the motor to lose torque. The motor will then try to compensate by pulling more current, in turn possibly burning out the fan motor windings.

After reading that, I had in my mind using a variac with a Split-Phase capacitor based motor (Vortex uses -- Which I use) I would be sure to have a fire at some point. My tests with a variac and this fan (and it seems what you guys are saying) indicate otherwise.

 

[rives]

Burning up the motor doesn't equate to starting a fire, at least if you have proper circuit protection.

As Jhhnn mentioned above, there are several fan manufacturers that are offering integral speed control in some of their products. I have a Fantech FG-6M-EC that is supposed to be 100% speed controllable, has integral motor protection, and higher levels of efficiency than standard fans, but I haven't gotten it installed yet. They are kind of spendy, but are very well built and the control is built in so there are no other associated costs.

http://www.fantech.net/FG-6M-EC_enus-49900.aspx

 

[Jhhnn]

Burning up the motor doesn't equate to starting a fire, at least if you have proper circuit protection.

As Jhhnn mentioned above, there are several fan manufacturers that are offering integral speed control in some of their products. I have a Fantech FG-6M-EC that is supposed to be 100% speed controllable, has integral motor protection, and higher levels of efficiency than standard fans, but I haven't gotten it installed yet. They are kind of spendy, but are very well built and the control is built in so there are no other associated costs.

http://www.fantech.net/FG-6M-EC_enus-49900.aspx

The price isn't bad as compared to fan + variac.

My S&P TD 150 developed a squeal in the bearing, so I contacted HVACquick where I bought it. A new one appeared on the porch 6 days later. Didn't even get an email confirmation, but I can't argue. I tore into the old one to see if I could change the bearing, but the way it's built makes that more than I wanted to deal with.

 

[Dropped Cat]

S&P mentions the Variac as the go to for speed control, so
that is what I use.

It's been four years 24/7, so I guess its okay. I have the 125, plugged
into the red Variac earlier posted, fan wired to full power.

 

[rives]

The price isn't bad as compared to fan + variac.

My S&P TD 150 developed a squeal in the bearing, so I contacted HVACquick where I bought it. A new one appeared on the porch 6 days later. Didn't even get an email confirmation, but I can't argue. I tore into the old one to see if I could change the bearing, but the way it's built makes that more than I wanted to deal with.

HVACQuick is a great place to deal with, that's where I get all of my supplies for that end of things.

 

[r2k]

Sorry to join the party two and a half years late, but there is a much simpler way. Just bleed off some of the outlet air with a hole or bypass. Put a damper vent on the bypass so you can control how much you want to release. Lots less messing with the electric and getting variacs and such.

If the fan is on the outlet and is pushing stinky air, you don't want to just dump that into your zone without filtering it. That's a wee bit more complicated but nothing that can't be managed. Just route the bleed off air back into a tee that feeds the intake. A portion of the air will go around and around.

There are a couple benefits to this approach. It can be much simpler to recirculate or bleed off air than to install speed controls. Some fans only like to run at one speed and will overheat if you try to mess with the power. It can also be cheaper to do this rather than buy a variac and wire it in.

-r2k

 

[Jhhnn]

Sorry to join the party two and a half years late, but there is a much simpler way. Just bleed off some of the outlet air with a hole or bypass. Put a damper vent on the bypass so you can control how much you want to release. Lots less messing with the electric and getting variacs and such.

If the fan is on the outlet and is pushing stinky air, you don't want to just dump that into your zone without filtering it. That's a wee bit more complicated but nothing that can't be managed. Just route the bleed off air back into a tee that feeds the intake. A portion of the air will go around and around.

There are a couple benefits to this approach. It can be much simpler to recirculate or bleed off air than to install speed controls. Some fans only like to run at one speed and will overheat if you try to mess with the power. It can also be cheaper to do this rather than buy a variac and wire it in.

-r2k

A big part of the reason for dialing down fans is noise reduction. Bigger fans at lower speeds are a lot quieter than smaller fans moving as much air at higher speeds. Otherwise, just buy the smaller fans because they cost less.

 

[rives]

And not "messing with the electric" would be akin to voluntarily stop breathing for me....

 

[BubbaBear]

Everyone needs to check out Hyper fans there half the wattage of a max fan and come with a speed controller.there 8inch fan blows 700 cfm and only 75 watts, they pay for themselves in power savings within a year

 

[chimei]

Just a follow up to my own question I asked in this thread because I was worried about what imnotcrazy has said several times on this forum about variacs, that it is NOT a good idea to use one with a parmanent split-phase based motor. Which many fan producers use, in my case I use Vortex.

Originally Posted by imnotcrazy View Post
Variac is NOT the proper method to control inline fans with Permanent Split-Phase Capacitor motors (Vortex, Canfan, Fantech etc). The ONLY reason a variac works to control fan speed is the voltage drop causes the motor to lose torque. The motor will then try to compensate by pulling more current, in turn possibly burning out the fan motor windings.
In motors such as P.S.C. type, you MUST use a Diac fired Triac type speed controller (such as the KB Electronics one previously mentioned) to prevent the current from rising and posssibly damaging the motor windings
Also Note: The Can Max fans have a DIFFERENT type of motor than the centrifugal type inline fans

I received word back from Vortex support that using a variac, is completely safe and they recommend using variacs with their fans that use Permanent Split-Phase Capacitor motors. because unlike using Triacs there is no hum at any speed.

They did say like other have, make sure NOT to set your variac so low that when turned on from a dead stop the fan cannot get up to speed.

 

[Dropped Cat]

Make sure NOT to set your variac so low that when turned on from a dead stop the fan cannot get up to speed.

That is easily tested, if the circuit is shared please test
under full load for your lowest re start setting.

Variac is a very good speed control device.

 

[theunforgiven]

KB Electronics has a "Vari-Speed" triac pictured on their site from the link rives posted on the first page http://www.kbelectronics.com/

Home Depot has it for $30 CAD.

http://www.homedepot.ca/product/vari-speed/402790

"KB ELECTRONICS Vari-Speed $29.95

The Vari-Speed is a motor speed control for air-moving applications that utilize shaded pole, permanent split capacitors (PSC), and AC/DC motors. This economical speed control is designed to replace obsolete, tapped winding, or reactive methods of speed control. The full-wave phase control circuitry minimizes power loss, thereby reducing energy requirements. The Vari-Speed provides infinitely variable speed adjustment which allows the end-user to select the desired level of air volume. It operates from 115 VAC, 50/60 Hz and has a maximum rating of 5,0 Amps at 40°C."