Fan motor circuit

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MetsFan

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Hi all,

I am using a self contained HVAC system, but I want to control the fan separately. The unit comes with a remote control that provides two fan speeds, so I want to be able to power and control the speed of the fan. The fan motor shows the wiring diagram below:

21835606348_8f97203203_z.jpg


Sorry for the blurry picture. The right side wires show GND, Vcc, and Output, which I assume is the 208V/3ph feed into it. The capacitor is a 3μF/400V. I don't know what the P and the circle with the squiggle are but hopefully one of you can tell me.

Typically, we would use a 0-10V or 4-20mA output to control the fan speed, but I'm not sure what this fan uses and I don't want to mess with it before I know for sure. Can anyone shed some light as to what I can do to control the speed?

I called the manufacturer, but didn't get too far. Either they don't know or don't want to share their proprietary information.

Thanks for the help!

 
The circle with squiggly line is your 208- 240 volt AC source. The "P" could denote a potentiometer for speed control. The output could send a over temperature signal to controller?? I am pretty sure it is not 3 ph because it has a starting capacitor.

Good luck.

 
Thanks Ship! You're right, it is single phase

Here is a different wiring diagram of the same unit but this one shows the entire logic board. Would the P be the triac shown here? If so, then maybe the Vcc is the speed control.

JFQHpv5.png


 
Vcc is typically referred to as the supply voltage. I also agree that this size fan motor is likely not 3-phase. It doesn't require a lot of HP and has a starting cap as Ship pointed out. The "P" indicator is generally the internal winding thermostat (often labeled P1 and P2) which can be wired in series to whatever type of relay/contactor control you are using.

I'm curious why you want to vary the speed of this fan considering it is low voltage and low RPM. Is this a work application or personal?

 
This looks like a closed channel type problem.

Hold my beer, I got this.

 
Vcc is typically referred to as the supply voltage. I also agree that this size fan motor is likely not 3-phase. It doesn't require a lot of HP and has a starting cap as Ship pointed out. The "P" indicator is generally the internal winding thermostat (often labeled P1 and P2) which can be wired in series to whatever type of relay/contactor control you are using.

I'm curious why you want to vary the speed of this fan considering it is low voltage and low RPM. Is this a work application or personal?


I might have to get a multimeter and check to see what changes when we switch from lo to hi.

Work application. It's a bit of a long story... I originally used a fan coil that had no sound data, but once installed, we were told it was too loud. We went through a lot of iterations with different types of fans and could not get down to their desired 48 dbA. I remembered the split units were pretty quiet, so we bought one to see if it would work. We hooked it up and it is super quiet, but we sold them on the ability to give them three speeds so that's where I am now.

 
Interesting. A DC motor might have been able to meet the required noise level. But looks like this is what you now have to work with.

Most motor applications that I'm familiar with deal with 480VAC/3ph/60Hz. And can be controlled via a multi-stage soft starter or the use of a VFD in vector/scalar control. This lower voltage might not play nicely with a Volts per Hertz control scheme.

It's difficult to make out the motor nameplate. What is the FLA (full load amps) on this particular motor?

 
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Yeah, I figured this would be an all in one solution and we wouldn't have to do much work to it. Unfortunately, I didn't think about the speed control until we had it.

FLA is 0.6

If I'm not able to figure it out, I'll have to put the remote within our control panel and have them vary the speed from there. It's not the cleanest solution, but it will work. If anything, we can set it at low speed and leave it there since that will give us the required CFM and BTU capacity while staying under that 48dbA requirement.

 
Yeah, I figured this would be an all in one solution and we wouldn't have to do much work to it. Unfortunately, I didn't think about the speed control until we had it.

FLA is 0.6

If I'm not able to figure it out, I'll have to put the remote within our control panel and have them vary the speed from there. It's not the cleanest solution, but it will work. If anything, we can set it at low speed and leave it there since that will give us the required CFM and BTU capacity while staying under that 48dbA requirement.
Where's your friendly neighborhood electrical engineer to help you out with this application? ;)

 
Yeah, I figured this would be an all in one solution and we wouldn't have to do much work to it. Unfortunately, I didn't think about the speed control until we had it.

FLA is 0.6

If I'm not able to figure it out, I'll have to put the remote within our control panel and have them vary the speed from there. It's not the cleanest solution, but it will work. If anything, we can set it at low speed and leave it there since that will give us the required CFM and BTU capacity while staying under that 48dbA requirement.
Where's your friendly neighborhood electrical engineer to help you out with this application? ;)


That's what you guys are here for, haha. We don't have any in the company.

 
Update: The three wires coming out of X27 in post #3 is what is controlling the speed. I wasn't there for the testing, but I was told there is no voltage difference when switching from high to low speed. That makes me think it's controlled through current, but I typically use a 4-20mA signal through two wires, so I don't know what these are.

When we unplugged those three wires, the fan automatically goes back to high speed. We are running out of time, so for now, we are going to set the remote to low and place inside our control box under a lock. We will put a relay in to disconnect the three wires so it changes to high speed. That way we can control the speeds through our PLC.

 
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