Square D Motor Starter coil failure

TFPace · Feb 20, 2021

I have a Square D motor starter that goes through a coil on a yearly basis. The starter coil is 480VAC also. I know there are plenty of starters that have a lower voltage coil but this starter is 480VAC throughout.

Is coil failure part of the wear parts for this device? Will switching up to a more modern type starter help matters? This starter is used on a 5 HP air compressor.

Thanks,

Tom

Phil in Montana · Feb 20, 2021

Does it Buzz when on?...Phil

TFPace · Feb 20, 2021

Phil,

No buzz. It's outside in a shed. I can take a screwdriver and press the pin on the left hand side of the coil and motor starts. I'm never around this pump to hear noises.

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TFPace · Feb 20, 2021

Pressing reset does nothing. The overload doesn't trip out

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cyanidekid · Feb 20, 2021

Not normal, and has mostly nothing to do with the voltage of the coil, I’d say.

Is there any other sign of frequent cycling, like burnt contacts, frequent clicking or possibly tripping of breakers or overheating (smells overheated, crispy black plastic )?

Is the unloader functioning properly? Is the unit properly sized to demand? Has other maintainance been done? (Oil changes, filters, etc)

If so, Could just be just a poorly designed starter. New or old doesn’t matter so much, absent other causes that’s not ok, should last 50 years or more, it’s just a coil.

(If it’s outside, can you rule out temperature extremes, bugs and moisture?)

9100 · Feb 20, 2021

What Phil was asking about buzzing is does the armature pull in tight against the fixed core? If not, the coil will draw excessive current and run hot.

Bill

rons · Feb 20, 2021

It's time to clean the metal parts in the entire works. I've done this and went a little farther to lap the metal laminated core on a diamond plate.
When the power is applied that thing clicks in tight. Don't lap the points or file them. Just brush them clean.

The coil should not wear out as you describe.

Phil in Montana · Feb 20, 2021

You have to put a amp prob on the coil and see what it pulls, The starter looks like it is getting wet or there is a lot of moister where live, if the iron is rusty the coil will see over current because the iron is not seating tight, might pay to find a new to you starter on ebay...coils arn,t cheap.be carefull 480 will kill.....Phil

TFPace · Feb 21, 2021

rons said:
It's time to clean the metal parts in the entire works. I've done this and went a little farther to lap the metal laminated core on a diamond plate.
When the power is applied that thing clicks in tight. Don't lap the points or file them. Just brush them clean.

The coil should not wear out as you describe.

Rons,

I change it yearly.

SomeoneSomewhere · Feb 22, 2021

You change the entire contactor/starter or just the coil?

Can you give us a rough starts-per-hour/day on the compressor and what model the contactor is?

Is it in a location exposed to condensation/significant temperature swings?

Pictures of the guts of the failed ones? How do you know they failed? Open circuit coil? Popped control fuse?

rons · Feb 22, 2021

TFPace said:
Rons,

I change it yearly.

Well. make this the year the last year to live like that. I'm already using vintage coils for the last 20 years. And 20 years ago my stuff was used. Well, not all of it.
There is some good stuff above the skanks...

metalmagpie · Feb 26, 2021

Calculate the current that should flow through the coil. Fuse it for slightly over that. Done.

Illinoyance · Feb 26, 2021

What is the actual voltage supplied to the coil?

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Square D Motor Starter coil failure

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