EKO Blower/Electric Motor Question

[Eric Johnson]

At the risk of sounding like a broken record, the new EKO controller, the RK2001UA, allows you to reduce fan output down to 50% in 10% increments. So these are obviously variable speed blowers. I knew that anyway, because the old controller, the RK2001E, modulates the fan speed when the boiler temp approaches the setpoint. Over the past couple of weeks since I put in the new controller, I've found that slowing down the blowers on my boiler results in significant efficiency gains. It's kind of like an overdrive, and nice in that you can fine-tune it for conditions. The only problem is that you set fan speed with a series of menus on the controller. I would prefer to be able to set it with a dial.

So my question is this: Can you modulate these blowers with a dimmer switch? And if so, how low could you dial it down to before burning out the motor?

 

[Fred61]

I'm no electrician (But I did stay at a Holiday Inn Express last night) but it is my understanding that a variable speed motor controller is different than a standard dimmer switch. (Price too!)

 

[Duetech]

Maybe they stop at 50% for a reason? In my younger days I used a dimmer style switch to slow a fan motor and ran it for hours and never burned it up. The idea could still be valid but I intend to price a new blower replacement motor before I take a leap in that direction.

 

[Eric Johnson]

I doubt if it's that simple, too. Just curious. I think I could get my wife hip to adjusting fan speed with a dial, but I doubt she'd have much luck setting it with the controller menu.

Anyway, that's one thing that I'd add to the controller.

BTW, you inspired me to start playing around with this thing, Cave, and I'm really happy with the results so far. Thanks.

 

[RJP Electric]

Typically when you want to regulate the speed of any A/C or D/C motor a variable frequency drive is required. When you lower the voltage you need to lower the frequency also. I was curious so I took some readings on my RK-2001E controller by changing the"N" setting. These are the results I got on my fluke meter

N 100 120V 60 HZ
N 90 103V 60 HZ
N 80 85V 60 HZ
N 70 71V 60 HZ
N 60 58V 120 HZ
N 50 48V 120 HZ

There is a frequency boost at the lower settings to get more HP at that voltage. It appears you can use a motor speed control (not a light dimmer), as long as you don't go under 71 volts. If you go lower the motor won't turn and you may cause damage.

 

[markpee]

Eric - What speeds are you running your motor at, and under what conditions?

 

[Eric Johnson]

I generally run it at 80-100% when starting a fire or loading it with very few coals. I think you need the extra draft to get things going good. Then, once I have the boiler heated up and producing a nice plume of orange flame, I turn it down to anywhere from 50-70%. That's when you get that nice blue flame and you get a longer burn. Most nights I set the fans at 50% and go to bed. Last night, for example, I loaded the boiler up around 11:00 and set the blowers at 50. This morning around 8 I went out there and found a nice bed of coals. I left it at 50 and put some more wood in and it took right off. It was down in the low teens last night, and all three zones in our house were above 70 this morning.

As Cave and others have documented in the "Fine Tuning your EKO" sticky, you're trying to achieve a sustained blue or white flame--not orange or yellow like they show in the videos. That's too rich. You need to lean it out for efficiency. The blower modulation helps you do that, along with the proper primary and secondary air adjustments.

 

[taxidermist]

Dont use a dimmer switch use a control for a celing fan as this controls a dc motor. I also have these switches for controling my pump speeds.

Rob

 

[tuolumne]

I don't know about the dimmer switch. However, these controllers run the fan right down to zero during the slow ramp up period and the ramp down period. I have my blower set at 50%, which is the lowest setting on the controller; when the temperature nears the setpoint, you can here the fan throttle way down. Clearly the fans are able to run at lower speed settings than 50%.

 

[slowzuki]

Three phase and single phase variable speed drives have a few differences. The three phase can be taken down to even braking on a VF rated motor. Even a regular motor can do it for a while, heat buildup is the issue. On a single phase you can't do the same and you notice the frequency boost to keep things happy. I wouldn't continuously run a single phase motor slower than that for long. You will probably find the run capacitor is not up to the task as well and will eat it. Its also inefficient.

If you want to do it long term, get a 3 phase motor and a real variable speed drive. A variable speed drive can usually be run on single phase if derated to about 66% of the rated power. Some tell you this in the instructions, others don't.

 

[Redox]

The speed of an AC motor is determined by the input frequency and the number of poles in the motor. A 2 pole motor on 60 HZ wants to run at 3600 RPM but with magnetic slippage will run about 3500 RPM or so. Varying the voltage will allow for more slip, but lets you slow the motor down. The amount of slip is largely load dependent and may not be very consistent with a reduced voltage motor controller. This is the reason for the 50% minimum speed. If the slip becomes excessive, the motor will stall and the current (and winding heat) goes up. Variable frequency drives change the frequency (duh!) as well as the effective voltage and operate with very little slip. Most motors on variable torque applications (fans) can tolerate a 10% minimum with a true speed drive.

I suspect that the ECO controller is of the variable voltage type as inverters are usually rather pricy. If I wanted to get all experimental and such, I would leave the ECO controller at 100% and insert a full wave speed controller in the circuit to the motor and use that to dial down the speed. Since I don't have an ECO (yet), I would have to leave this to others to try. I was under the impression that the ECO controller would vary the speed based on conditions, no? I thought that was supposed to be a good thing.

Chris

 

[Eric Johnson]

The EKO controller does modulate the fan speed as the boiler temp approaches the setpoint, but I don't know how much good it does. The new controller allows you to manually set it to from 50 to 100% in 10-point increments, which I found to be very useful in extending burn times and keeping the boiler from idling excessively. Like Cave2K (and others) says, shoot for the blue flame instead of the orange they show on the video clips. Blue is a cleaner burn.

Some of the fancier Euro gasifiers use lambda sensors in the exhaust to regulate blower speed, and perhaps even air settings. Now that's slick. Or "sick," depending on your DOB. I'd be happy with controller/air presets that you could select for various conditions: wood moisture content; ambient temps; draft conditions, etc. You could chart out what works best, and then select the "session" that corresponds to the situation. Given the experience and diversity of the people on this website, we could put a comprehensive "book" together in a couple of weeks, I suspect.

 

[DaveBP]

WOULD YOU GUYS STOP IT!!

I haven't even got my Tarm installed yet and you have me thinking about mods involving aquastat/relay/solenoid combo's running fan-speed switches and sliding the secondary air controls over to 2 or 3 settings.

Seriously though, this forum is my single greatest motivator to finish building my house; so I can start messing around with this stuff, too.

If it ain't broke... tweak it?

 

[overshot]

First determine what type of motor it is - then see what is available to control it. Is it a permanent capacitor motor? Most fan motors are and they can go down to 50% speed just by varying the voltage.

 

[Eric Johnson]

Does this help?

 

[88rxn/a]

lurks for input......

 

[Redox]

Actually, I recognize those EBM motors. Our drives use several different motorized impellers from EBM. They are very rugged, long lived and usually expensive. The M2E is a PSC design that can be run very slowly with an appropriate controller. The R2E looks like it is a shaded pole design that isn't as efficient, but should be controllable to at least 50%. The third one I don't recognize.

Just about any full wave controller should be good enough for these motors. The ceiling fan types are probably the most readily available and lowest cost. I think you can get a 3 amp control for about $20-25 from Grainger. They usually have an adjustable minimum that allows to keep the motor from stalling. I just don't think they are very accurate at low speed and may require a little tweaking to get the RPM just right. You would have to go to a three phase motor and drive for really tight control.

Dave: I know what you mean. I want one of these things so bad, I can taste it! The tweakability factor is incredible and would keep me entertained for a loooong time.

Chris

 

[rcollman]

Love this forum.

Saw a mention in another thread about the EKO fan controller. Got me thinking about my Solo40. You people are way ahead of me with your fluke meters

Prior to finding this thread, I did a general Google on Fan regulators, which led me to fan regulators/ motor controllers. I saw one brand, looked like a solid state unit, ON-OFF switch built into the variable dial, snubber network (oh yeah another wikipedia lookup), and an inductor capacitor network provides electrical noise suppression. Will something like that work with my Solo40?

From what I gather, reducing the cycle time when the fan is off is good, having a blue flame is better and of course extending the time between loading fuels is nice. Question: On "warm" days if I cut my fan down to 80% , will that improve things, like having more coals in the firebox after a hard day of pounding keys?

I am sort of guessing that if it were a great idea, then BioHeat would include it as an accessory, like the tubolators. Is this another 3% improvement. "Watch the pennies and the dollars take care of themselves", old yankee saying, so comments?

 

[easternbob]

Redox,
I'm not much of an electrical guy but I'm interested in slowing the fan on my EKO25. I have the old controller and looking for ways to increase the effiecency and burn times. I took a quick look at Grainger and couldn't find the controller you were talking about. Any chance you could post of link or maybe an item number.
Thanks,
Bob

 

[Redox]

The Grainger one I was referring to was a 5C203, but now that I actually look around, they have an even cheaper one from Leviton. Look at the 5C343 or the 4W205 for even less $$. Any controller marketed for a ceiling fan should do the job. Good luck!

Chris

 

[easternbob]

Chris,
Thanks for the specific item numbers. Looks simple enough.

I assume I can make some marks on the cover to correspond to the fan speed percentage's that RJP Elec. got off his unit?

N 100 120V 60 HZ
N 90 103V 60 HZ
N 80 85V 60 HZ
N 70 71V 60 HZ
N 60 58V 120 HZ
N 50 48V 120 HZ

 

[Redox]

No problem! The only problem that I can forsee is if the fan stalls at an abnormally low setting. You might set the minimum up kinda high and that gives you a wider range on the main control. I'm guessing that at less than 50%, the boiler isn't going to be supporting much gasification which is really where you want to be. Think of it as the minimum stop on an EPA stove to keep them from smouldering. Just me, but I would put a piece of tape on the faceplate for marking as this is all just a big experiment anyway......

Chris

 

[DaveBP]

Interesting, Eric, but my Tarm Solo 40 has the same fan as one of your photos; the M2E 90W unit.