Varying the speed of a single phase fan.

[BACnet]

I've got a fan speed application that I'm running into a wall on and I thought that perhaps someone on this board might be able to give me a suggestion.

The fans themselves are very small - single phase, permanent split capacitor, some 115VAC and some 230VAC, all less than 1/2 hp. The problem I am finding is coming up with some way to tie them into my control system.

There are a lot of companies out there that make wave choppers that can control such a fan application, but all that I have found have a pot controlling them manually. What I need is some sort of 0-10V or 4-20ma input on such a device but I'm coming up short. (And I don't want to have to duct-tape an actuator to the potentiometer, this is a commercial application, no shortcuts allowed).

I already put this question to JslimJeff and he was nice enough to suggest a couple of SCR's might be made to work, presumably in an "inverse parallel" configuration if I wanted to drive them at a high enough frequency. This is an approach I may yet take but I was hoping that there was already a device on the market that would just take a standard current or voltage signal input and do the dirty work for me.

Anyone run into this problem before? Are there any devices you've purchased that can tie single phase fans into a control system?

Thanks in advance for any help you may have.

[billcontrols]

JCI S66 Fan speed control

bill

[BACnet]

Thanks bill, I'll check that out!

[control$]

I've used Nimbus for 110vac VFD control. No real issues.

[amigo]

I've used Nimbus for 110vac VFD control. No real issues.

another one for nimbus, look into them if you like.

[orion242]

Nimbus is a cheap way to get the job done. I would not use it on pumps though, my fish tank filter pump was not to happy with it running < 75%.

[printer2]

Is there much of a market for 0-10v input single phase motor speed controllers?

I know some people that do lighting/ventilation controls for the agriculture market but while they do fan controls the only 0-10v controller they have is for lighting controls. While listed as a three phase slave it controls one phase, it is meant to expand their regular controller for anyone that has 3 phase lighting circuits.

http://www.phason.ca/plc2sdc.htm

The only issue would be the response curve which is set up for lighting applications. They would have to change the response for fan control.

I live in a 3 phase world so I do not know if many people need a single phase speed controller with a voltage or current input.

[perfectionist]

BAC.... are you trying to control pressure or temp of air?

[BACnet]

Actually it's CFM that I'm controlling. The controller works great, the application is done and all that.

My only issue was that unlike a 3 phase motor, these little things can't use a VFD. Luckily it looks like both the JCI and Nimbus options would work quite well. The cost difference between them is less than five bucks, so I may want to pick up one of each and put them both through their paces.

Mods- I know I mentioned "price" here, but not as an absolute, I hope this is acceptable.

[perfectionist]

The controls I use wok well with psc motors. the FAC-120 controls cfm by way of temp. The Zone Handler controls by pressure. Great support too. http://www.fanhandler.com

[crab master]

Which one did you use and which one did you like the most? I've got an exhaust fan application based on room pressure.

Even though you mentioned the 5 buck difference the Johnson requires a 24VAC transformer that doesn't seem to be included...

[BACnet]

I started out with a Hoffman 709D. It was a very straight forward fan controller with one exception- it was a complete and total piece of junk.

There are potentiometers on the Hoffman board that need to be spun to set the minimum & maximum speed that it will run the fans. Adjusting one of them effects the other, so you end up tuning it endlessly to get the fan to hit your min and max targets. What's worse is that when you give it a full signal (10V or 20ma) it will latch and the only way to regain control is to give it zero signal for a few seconds, then once the fans spin down to almost a complete stop you can once again use the controller to vary their speed.

As a result of the complete failure of the Hoffman design we spec'd a second unit. This time we used a JCI S66AA-1. This wave chopper isn't identical to the Hoffman- it actually ramps the fans up to full speed for a few seconds when you power it up, then it drops them back to your control signal level. This starting feature had originally been accomplished in the controller driving the chopper circuit but by cutting out that logic and relinquishing the startup stuff to the chopper, all went extremely well.

So what I found was that these circuits are not identical and certainly not interchangeable without modifying the circuit driving them. (Due to one having the startup feature and the other not having it). But I would avoid the first one I tried to use. When you give a unit a control signal and it simply ignores it and runs the fan at full speed it can cause all sorts of hard to work-around problems. Use the JCI. :.02:

[crab master]

Thanks, eliminates one.

I am also looking at http://www.aircareautomation.com/data/acv108x.pdf

Nice that they have communication capabilities and price seems reasonable, but awaiting my price on the S66.

[digo]

BACnet, are these motors by chance ECMs?

I'm working on a data-center job where each cabinet has one of these, and this is the interface we're using to control the speed:
http://www.gotoevo.com/acu%20Series%201%20product.htm


ECMs are DC motors that function using a built-in inverter and a magnet rotor, and as a result are able to achieve greater efficiency in air-flow systems than some kinds of AC motors. (Although AC current is used for ECM, the ECM’s internal rectifier converts the current to DC voltage). Permanent split capacitor (PSC) motors, often used in conjunction with electronic SCR motors, are somewhat inefficient when used in air control systems because the fan motor noise requires the motor to run at less than a full load. When turned down, PSC efficiency suffers and falls in the range of 12 to45 percent. ECMs, on the other hand, maintain a high level (65 to 75 percent) of efficiency at a variety of speeds. As a result, ECMs are cost and energy efficient and can reduce operating costs. Additionally, ECMs are not prone to overheating and do not require additional measures to offset the generation of heat, as PSCs often do.

ECMs are also relatively low-maintenance; the use of true ball bearings reduces the need for oiling, and varied start-up speeds reduce stress on mounting hardware. The operating range is significant enough to enable one ECM to replace two induction-style models, which simplifies the replacement, maintenance, and installation processes, and minimizes product choices. However, not all ECM motors run at variable speeds and selection depends heavily upon application specifications. The initial cost of an ECM can be high, but is typically balanced by overall energy savings in the long run.

[BACnet]

Digo- No, these are standard Permanent Split Capacitor (PSC) 110VAC motors.