Fan Speed Control

[ajriding]

Im looking for a fan speed control.
Please dont post your internet search results here. Anyone, including me, can do a search and find mindless stuff. I am looking for specific knowledge, thanks

The Fantastic fan has 3 speed. High, but the Low and Med are regulated with a heating element, so running low save no electricity, and might even use more.

I would like to wire in a speed control that uses less energy at lower speeds (that doesn't just burn off electricity in the form of heat to reduce current to the fan).

I have a PWM controller that worked fine. I let it run all night on a low setting with no issues, and today I left it on a few hours on a higher speed (less than full though), and went back to find it burned out, and hot. The default setting if something happens is to just put out full power, so the fan was running on high.
When it worked it makes a ringing sound at the fan.
I cannot find the exact match, but it was similar to this one on eBay, same case at least.

IDK why it burned out, it is rated at 8 amps, and the FF is about 2.

So, Im trying to figure out what controller will do what I want.

I have another controller, but it has a really big heat sink, so I assume it will waste power making a lot of heat.

[ajriding]

yea, the computer fans are great, but not for replacing the way more powerful FF motor. Maybe using one to blow air in from a window would help move air out the roof vent and that could be a compromise solution.

I have a second vent that is not FF but also not covered bc the solar panels are right there and I cannot shade the panels and cannot really leave the vent open all day and be gone due to the constant haarp rains all the time getting inside.

I ordered that controller in the link and will drill out some vent holes to help cool it. Hopefully the ringing of this one is out of my hearing range too

[FWC]

Gdetrailer wrote:


Which is why I am saying you are going down a rabbit hole.

You have two different "efficiencies" at work here.

1 is current draw of the inefficient brush can motor.

2 is lack of air movement of the fan blade design.

This is why I mentioned trying a computer case type of fan, the motors are high efficiency brushless PWM controlled motor and well designed fan blades that make the most of getting max air flow for the RPMs.

If you dig around you can find a 4" computer case fan that draws less than 1A and gets well over 100 CFM of airflow which is more than twice the airflow at 1/3 the amperage of what you now have. Get the right one that runs at a lower RPM and they tend to be very quiet also as a bonus.

HERE is just one example. That example is rated roughly 70 CFM at a noise level of 25 DB which is very quiet and runs at 1700 RPM max at 1.08W of power. 1.08W at 12V=.09A!!

Yes, you read that correctly one watt of power an yet get 70 CFM of air flow.

Full specs can be found HERE

The only downside to computer case fans it they are not designed to be reversible, but buy two for one each direction and switch between them.

I have converted my trailer fans over to computer fans yrs ago, much less noise with a lot more air movement with a bonus of less current draw.

This is all true about brushless motors and better fan designs being much more efficient. However it is also true that a simple and cheap PWM controller can significantly increase the efficiency of the existing fan on all but the 'max' setting. Re-engineering your fantastic fan to use a PC fan is a pretty major undertaking, adding a PWM controller in line with it is fairly easy.

[TurnThePage]

I have several fans controlled by PWM. One of them is a Surflo product (similar to the FF) that is no longer manufactured. It has brushes but has run flawlessly for years and move tons of air. I installed the original version of the Heng's Vortex in the bathroom, then added a PWM to it. It really moves a lot of air, but can get noisy (wind noise) at top speed. I also have a fan that is intended for the windshield area of a motorhome, but I use it for the bed area. I added a 12.5 khz PWM controller to it that works excellently with no noise that I can hear. The Surflo fan has the highest draw at 2.1 amps on full speed. I'm a firm believer in this technology. It's worked great for me. It's awesome to be able to select virtually any speed you want.

[Gdetrailer]

ajriding wrote:

FWC wrote:
From my Victron BMV-712.

The FF does have brushes, but not user serviceable. Quite frankly the Fantastic Fans, like most RV appliances, are total junk designed in the 1980s.

Agree, it is amazing how little air the ten blades actually move for such a large motor and fast fan speed... I often wonder if the FF was originally designed as a blender instead of a fan.

Was your 0,9A reading on a speed equal to the Low setting? Im interested what it is on the speed where the fan barely has enough power to turn, it has to be much lower than 0.9..
3A on high, 2.3A on medium and 1.9A on low.
PWM 3A, 1.6 and 0.9A

Which is why I am saying you are going down a rabbit hole.

You have two different "efficiencies" at work here.

1 is current draw of the inefficient brush can motor.

2 is lack of air movement of the fan blade design.

This is why I mentioned trying a computer case type of fan, the motors are high efficiency brushless PWM controlled motor and well designed fan blades that make the most of getting max air flow for the RPMs.

If you dig around you can find a 4" computer case fan that draws less than 1A and gets well over 100 CFM of airflow which is more than twice the airflow at 1/3 the amperage of what you now have. Get the right one that runs at a lower RPM and they tend to be very quiet also as a bonus.

HERE is just one example. That example is rated roughly 70 CFM at a noise level of 25 DB which is very quiet and runs at 1700 RPM max at 1.08W of power. 1.08W at 12V=.09A!!

Yes, you read that correctly one watt of power an yet get 70 CFM of air flow.

Full specs can be found HERE

The only downside to computer case fans it they are not designed to be reversible, but buy two for one each direction and switch between them.

I have converted my trailer fans over to computer fans yrs ago, much less noise with a lot more air movement with a bonus of less current draw.

[FWC]

My ~0.9A reading was at a speed kind of equivalent to the prior low speed. The current doesn't actually drop that much more when you go even slower, there is a certain amount of energy to overcome friction and that is lost in the motor windings, so the current isn't linear with speed. I don't remember what the minimum current is though.

[ajriding]

FWC wrote:
From my Victron BMV-712.

The FF does have brushes, but not user serviceable. Quite frankly the Fantastic Fans, like most RV appliances, are total junk designed in the 1980s.

Agree, it is amazing how little air the ten blades actually move for such a large motor and fast fan speed... I often wonder if the FF was originally designed as a blender instead of a fan.

Was your 0,9A reading on a speed equal to the Low setting? Im interested what it is on the speed where the fan barely has enough power to turn, it has to be much lower than 0.9..
3A on high, 2.3A on medium and 1.9A on low.
PWM 3A, ,,,1.6 and ,,,,,,,,,,,,,,,,,,,, 0.9A

I also realized that my electric fridge only pulls 3-4 amps, and it only runs some of the time, so the fan on high would be the biggest drawdown on batts. wow. Even with the fan pulling 1 amp it will still be the biggest draw since it runs all the time vs fridge running a fraction.

[FWC]

From my Victron BMV-712.

The FF does have brushes, but not user serviceable. Quite frankly the Fantastic Fans, like most RV appliances, are total junk designed in the 1980s.

[ajriding]

Interesting. Two conflicting reports, but good topics.

FWC, how did you get the Amp numbers?
Yes, 10AH seems to be significant. In reality, not 10 hours, but from about 4pm to 10 am is 16 hours for us solar users who might be stuck in camper in bad weather. 16aH, or on a cloudy day it could be 24 aH and very little solar charging happening... Thus, the reasons for my interest to eek out every last wave of electrons...

For the daytime, when I am gone and just want vent to run, I would run it on absolute lowest possible speed, so less than half the speed of what the Low setting is, so yes, a computer fan would work too, but easier to put in the controller than wire in another fan and deal with it.

Keep in mind I have a DC fridge and the batts are already about 7 years old, so already running a clip fan all night is noticeable difference in voltage when I wake up. I want to avoid any deep discharge of the battery so I never go too low and I want batts to live as long as possible, yet I want to have the fan run when I want it.

I didnt know the FF has brushes, that's good to know if it ever stops.

[FWC]

For reference the 'classic' Fantastic Fan model 4000R draws ~ 3A on high, 2.3A on medium and 1.9A on low. Using a PWM controller, dialed in for what appears/sounds to be about the same speeds medium and low I am seeing 1.6 and 0.9A, so a saving of about 0.7A on medium and 1A on low. I use about 30 - 50Ah a day, so if I were to run the fan overnight on low using my PWM controller, the reduction of ~10Ah would be a noticeable saving.

With a PWM frequency around 20KHz or so there is nor ringing or noticeable increase in noise. There is no output filtering on any of these PWM controllers (the inductance and inertia of the motor takes care of that) and on full on there are no 'conversion losses' when the controller is at full speed. Many of us have been using PWM fan drivers for years, so clearly they and withstand the current spikes from field collapse, maybe they have a fly-back diode across the output.

[Gdetrailer]

ajriding wrote:
No, just two issues that really matter.
1. Wasting electricity on the heating element-looking thing (wasting time talking about whether it is a heating element or a resistor), and
2. what controller is most efficient.

Heating up a coil might be a small amount of power in your mind, but do that all night long using a battery that is powering other things might just be enough to run the battery too low after a few cloudy days in a row. Run the battery too low and you got bigger problems than unrelated post.
It's all about the battery. Not everyone understands this. I know some people hop campground hook-up to campground hook-up, but others require everything from a battery set-up.

Instead of guessing, one day I might wire in an amp meter and actually measure the difference between High speed (no resistor), Medium and Low speed.
Eventually someone on forum will have already done this. I appreciate the guess on how much power the settings might use.

Your not going to "save" enough energy wasted by changing to PWM to noticeably increase the time between battery charges or shortening the time it takes to charge the battery.. We are talking maybe minutes at best per day.

PWM controller will eat up a lot of your "savings" in wasted power depending on the "speed" you want the fan to run.

At "full on" your PWM controller will be ADDING it's conversion losses to the wasted energy of the fan motor causing you to actually use more battery than if no PWM was connected.

The fan motor you are using is highly inefficient to start with, it will be a brush type "can" motor with a simple sleeve bearing. Basically late 1890's DC motor design, there is nothing efficient with that motor..

PWMs also have another narly side effect, NOISE. Most cheaply designed PWMs do not filter the output, this results in your motor windings giving off a vibration which depending on frequency may be in your hearing range and may sound like a whistle. Unfiltered PWMs will also have considerable switching harmonics, those harmonics are not "usable" energy and result in your motor burning up as wasted energy rather than constructive usable energy.

The brush motor also can cause considerable issues with backfeeding the PWM controller with brush noise and inductive spikes full of harmonics out of phase with the PWM.. PWM controller may not like that and I suspect that is why yours burned up on you..

If you really want to reduce your battery useage, you would need to hop up to basically a brushless motor like what is used in computers. Those are far more efficient energy wise than a brush type can motor.

Don't get me wrong, PWM under the right use and correctly done can save a couple of watts of lost power, but in the case of small motors, not much savings to be had to make this endeavor worth it.

Try a computer fan, bet it will move as much air or more at half the wattage than the motor you have now.

[ajriding]

No, just two issues that really matter.
1. Wasting electricity on the heating element-looking thing (wasting time talking about whether it is a heating element or a resistor), and
2. what controller is most efficient.

Heating up a coil might be a small amount of power in your mind, but do that all night long using a battery that is powering other things might just be enough to run the battery too low after a few cloudy days in a row. Run the battery too low and you got bigger problems than unrelated post.
It's all about the battery. Not everyone understands this. I know some people hop campground hook-up to campground hook-up, but others require everything from a battery set-up.

Instead of guessing, one day I might wire in an amp meter and actually measure the difference between High speed (no resistor), Medium and Low speed.
Eventually someone on forum will have already done this. I appreciate the guess on how much power the settings might use.

[Gdetrailer]

ajriding wrote:
ok. good points.
I dont think my fan is worn in any way. The noise is a ringing, not a mechanical issue. The controller I showed , as I mentioned, is similar, and I am not able to find anywhere the exact controller online anywhere to be able to look at its specifications... It might operate in the human ear range and be audible.

The FF has coils that act like a heating element to burn off power. However you want to exactly define what a heating element is or not does not matter bc in the end it still is doing the same thing, heating up a wire at the expense of power. I thought I used words to give clues that this is not important nor something that matters or needs further discussion. What I keep try to say politely is that I dont really care if you call it this or that. Nothing changed now that you defined it. It is hard to write on a forum post something that can both be understood and polite, I tried. Now lets stop with the heater analysis....

Your chasing a lot of rabbits down the rabbit hole.

Yes, a resistor will waste some energy as heat, but it isn't as much as you think.

Your fan motor will draw max current (max wattage) when full voltage and load are present.

Insert a resistor and the motor now sees less voltage and that in turn slows the fan blades lessening the load the fan sees which reduces the current drawn through the fan motor and resistor.

We are talking on the order of a couple of Watts worth of power being shed as wasted heat.

PWM controllers while they can reduce SOME of the wasted energy over a resistor can in fact use more energy than one realizes. PWM controllers do get hot, that heat is wasted energy from the controller's output transistors.

Typically the most energy you are going to save may be on the order of 1W or less on small low power applications such as a small fan motor..

Not to mention, you have now added a bunch of complicated circuitry with the potential to break down easier and to create a lot of RF noise in the process..

[frankwp]

ajriding wrote:
ok. good points.
I dont think my fan is worn in any way. The noise is a ringing, not a mechanical issue.

The noise is a function of the PWM controller. The high speed on/off switching that is used to effectively lower the voltage produces the high pitched sound. You probably noticed that at full speed the sound goes away or is greatly reduced. Some controllers are noise, some not. BTW, The noise is mostly generated at the motor, not the controller.

[shastagary]

i always buy a speed controller that handles way more amps than the fan draws they will run cooler and last longer. i am using one like this from ebay for 7 years now 40A DC Brush Motor Speed Control PWM

i am running a 12" car radiator fan i mounted in my vent cover that draws up to 8 amps. i also bought a 6 channel remote control relay circuit and have it switch different resistances for the speed controller instead of the variable control on the speed controller.

[ajriding]

ok. good points.
I dont think my fan is worn in any way. The noise is a ringing, not a mechanical issue. The controller I showed , as I mentioned, is similar, and I am not able to find anywhere the exact controller online anywhere to be able to look at its specifications... It might operate in the human ear range and be audible.

The FF has coils that act like a heating element to burn off power. However you want to exactly define what a heating element is or not does not matter bc in the end it still is doing the same thing, heating up a wire at the expense of power. I thought I used words to give clues that this is not important nor something that matters or needs further discussion. What I keep try to say politely is that I dont really care if you call it this or that. Nothing changed now that you defined it. It is hard to write on a forum post something that can both be understood and polite, I tried. Now lets stop with the heater analysis....