Speedaire Compressor contactor problem

Not sure if this is the right place for this post, feel free to move if necessary.


I purchased a Speedaire Compressor off Craigslist last night. It's an older model, but has similar specs to their current, flagship models:
Three phase, 7.5 horsepower, 24.3 CFM, upright compressor with an 80 gallon tank. The motor is dual voltage, 208-240/480. I believe this model is a 1ed63, but I'm having difficulty verifying that. The main difference between this model and current models seems to be motor efficiency. The specs on the current models list lower FLA values for the same output. Current units operate at 19 or so amps while this motor lists 21.6 amps to start.

Unfortunately I was unable to test the unit prior to purchase as three phase power wasn't available. I got the machine to my shop and plugged it in to a 20 Amp circuit. The contactor contacted and the motor spun, but much slower than the listed 1750 RPM. Check the motor connections and determined the wiring was for 480v, not 208. Rewire the connections and now the motor spins at the proper RPM, but will only operate if I manually hold the contactor down. Aside from that the operation of the machine is as it should. It compresses air and the pressure switch does shut off the unit.

Is there a possibility that running the motor on too low of voltage damaged either the motor starting relay or contactor?

Do I need to change the thermal units to reflect the difference in ampacity from 208 to 480?

The motor starter in this unit is a Furnas
Cat no 16BF35AGASY
PN P14178A
Again, a rudimentary google search yields very little other than specs on this specific unit. I imagine it too has been superseded by a more current unit.

Anyhow, I'd rather not buy another motor starter if this one can be salvaged, but will gladly accept any advice as to testing and diagnosing the problem.


Thanks all



Jeremy


Sent from my iPhone using Tapatalk

Your thread title should be asking this question..

If the contactor coil is high voltage then it will not activate. That is why you have to manually hold it down to make contact. If the coil is replaceable then your can swap it out from a 480 to a 220-240 one.

I will research that possibility. The fact that the contactor worked properly, even though the motor was wired improperly, makes me question this though. The contactor runs off one leg of the three phases. In my case that's 208V, three phase, so each leg is around 110-120V. That voltage activated the coil initially, even though the motor was wired wrong for the incoming voltage. Am I missing something?


Jeremy


Sent from my iPhone using Tapatalk

Show a wiring diagram, I don't know if you have a control transformer. Look at what the coil voltage is on the contactor.

Here's what I'm working with:





Sent from my iPhone using Tapatalk

Do you know what that green push button is for? It resets the overload circuit.

If the controls were originally setup for 480 volt operation and you rewired the motor for 220 volt then the overload heaters have to be changed out for a value which corresponds to the new connection voltage. If you look at the motor nameplate you can see what this all means. As it is the contactor will disconnect your motor because the heater values are too small.

Take a picture of both sides of the Furnas. You have plenty of slack in the wiring to remove the contactor from the metal box and rotate it around and see if the coil has a label on it. Is there a designation showing what the coil voltage is? Do you know what a coil is? I suspect you are going to have to make some changes.

The overload hasn't tripped, at any point.
I understand Ohms law and that the amperage requirements of the motor decrease when the voltage increases. I'm starting to put the pieces together; the thermal couplings are "tuned" to 480V and the corresponding 10.1 amps. The resistance created prevents the contactor from fully seating and running the motor on its own. Hence the system running when I force the contactor in. I imagine the coil is the secondary portion of the motor controller that holds the thermal couplings? Am I warm here?

If so, advice time. This controller is obsolete. Parts are probably available, but google indicates that it has been superseded in almost every way. If the coil and thermal couplers need to be replaced, should I just save myself the time tracking down parts and try to source a new, (to me at least) three-phase, 208V motor controller with appropriately spec'ed thermal couplings?

Ultimately, I have a couple more days in which to decide to keep this machine or return it. I'm not in it too deep right now but more than a couple hundred more dollars in parts or my time makes this compressor a bad deal.


Jeremy


Sent from my iPhone using Tapatalk

Just as in post 6 above your contactor is not latching because the coil is most likely 440/480 volt.
However I would be most concerned as to why the red lead from input shows signs of arcing/melting .
The black from arc flash on the ear for the contactor mounting tells me there is more to this story.
The coil should show operational voltage on it.
Change out heaters for correct FLA listed on motor for the voltage you are now using.

jermfab said:

The overload hasn't tripped, at any point.
I understand Ohms law and that the amperage requirements of the motor decrease when the voltage increases. I'm starting to put the pieces together; the thermal couplings are "tuned" to 480V and the corresponding 10.1 amps. The resistance created prevents the contactor from fully seating and running the motor on its own. Hence the system running when I force the contactor in. I imagine the coil is the secondary portion of the motor controller that holds the thermal couplings? Am I warm here?

If so, advice time. This controller is obsolete. Parts are probably available, but google indicates that it has been superseded in almost every way. If the coil and thermal couplers need to be replaced, should I just save myself the time tracking down parts and try to source a new, (to me at least) three-phase, 208V motor controller with appropriately spec'ed thermal couplings?

Click to expand...

Not warm. Luke warm.
1. The coil is replacable (usually) and is connected by two wires. The coil can be 24, 110, 220 Volt AC, etc.
If you were really desperate you could tear into the existing one and rewind it for lower voltage.

2. Those spring looking things are the heaters. They are TOTALLY separate from the coil and are chosen to match the particular motor.

You need both 1 and 2. If I was making the decision the condition of the tank is what I would be looking at along with the pressure switch. The entire motor controller can be replaced for a newer model. Used ones don't cost THAT much. One here has a wide range for overload current, 2.5 - 10 A.

New motor controller has been ordered.


Sent from my iPhone using Tapatalk