Dairy ventilation

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ptonsparky

ptonsparky

Tom
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
I have a customer that is having a hard time keeping his ventilation fans running in his dairy. There are some obvious wiring problems but I also need to make sure the speed controls are being applied properly. The control is Del-Air and varies the voltage to single phase motors via a Monitrol DEL002528 or...23.

Any of you familiar with these and their operating capacities? I haven't been able to find them.
 
First, are motors designed for variable speed. They need to be shaded pole or PSC. Most anything else will not work.
 
kwired said:
First, are motors designed for variable speed. They need to be shaded pole or PSC. Most anything else will not work.
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I imagine this might be the issue. From the looks of it, the Del-Air fans are PSC and thus would be suitable for the application. But if your user bought the Del-Air controller and used his own fans, he may have ended up with Cap-Start or Split Phase motors. If so, using them on inverter drives will set up a race to see what fails first, the motor or the drive.
 
Can they switch to 3 phase? All the fans on the dairies around here are 3 phase, aside from the portable fans/swamp coolers.
 
He has 48 2hp stainless steel motors on the roof with another 16 circulating fans on the inside. Might be a bit of an expense. The roof top ones need repiped so we will make room for a change to 3ph when we do that. Close to 1K feet. They are not all speed controlled.
 
ptonsparky said:
He has 48 2hp stainless steel motors on the roof with another 16 circulating fans on the inside. Might be a bit of an expense. The roof top ones need repiped so we will make room for a change to 3ph when we do that. Close to 1K feet. They are not all speed controlled.
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Wow yeah, that would be expensive. Have you looked at the current draw on the speed controlled units? Is the controller maybe having trouble with the distance causing a VD and making the motors draw excess current? I know it's difficult to see motor current with an ammeter if it's a PWM drive output, but it looks like some of those controllers have a display option, can it show you the motor current?

Could just be a poor design on the speed controls too. There are only 3 mfrs of 1 phase VFDs that I am ware of (plus several brand-labels), I've heard that one of them, made here in the good ]ole USA, is a piece of junk, but I have no direct experience with it. I've used the Invertek (which is also branded as the Anacon and several others), it's a good solid drive, but it's also expensive. From the looks of the manual it seems Del-Air may be incorporating a small inverter drive into their PC board that does everything else, but it's had to tell, they are a little shy on details. It'd be interesting to find out exactly what that unit is doing to vary the motor speed.
 
Learned again, customers memory is not always to be trusted. 2 amp motors, not 2 HP. Makes vd calculations different that is for sure.

Looks like company is out of business. Phone #s and email no longer work. Fasco mfgd OEM style fan motor is no longer available. Speed control is a triac with the assembled controller rated at 15 amp max. Pretty fancy system when it was installed.

Customer wants low priced fix that works. Sound normal?
 
Triac speed control will only work if they use Shaded Pole motors. If they are PSC motors they will overload or the triacs will fry. Different race, same results. A triac can only affect the average voltage going to a motor, not the speed. When you reduce the voltage you reduce the torque, which in some cases ends up reducing the speed. But that also increases the slip and in anything other than a Shaded Pole motor design, causes the motor to draw more current as it tries to return to full speed. More current, less work = overload.
 
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