Contactor disengages when grounded?

[mark32]

Hey Guys!

A friend of mine is a handyman, but was asked by a customer to change out a motor on some machinery in a machine shop, which he did. Afterwards, all seemed well enough, but either he or the shop foreman decided to change the contactor's coil. At the same time, for whatever reason, my friend switched around some of the conductors coming off of the secondary of control transformer (208 to 120). So, while holding the contactor in his hand, he hits the start button, the contactor engages, the motor runs, everyone is happy. He then goes to screw the contactor back into it's enclosure, and the motor instantly shuts off as soon as the contactor touches the enclosure. Then, with the contactor floating, he hits the start button, the motor runs, but all shuts down again when the contactor makes contact with the enclosure. He took a sheet of rubber and sandwiched it between the contactor and the panel and all is well for now. I may look at the install in another week or so for him, I'm assuming the control circuit is opening but can't understand why. What do you guys think could be causing this to happen?

 

[tom baker]

It’s related to control transformer wiring change.,,,

 

[hillbilly1]

I would say a short in the coil, the transformer may have had a floating output, but when the wiring was changed, it had one side bonded, now the short drops the control voltage to release the contactor, but is quick enough not to blow the control fuse, if there is one. Just a place to start. Check for voltage from contactor to ground when it is energized, but isolated.

 

[jim dungar]

It’s related to control transformer wiring change.,,,

In the old days it was not uncommon to 'ground' the X1 side of a control transformer while fusing the X2 terminal. I have seen several cases where a troubleshooter identifies this as the problem with the machine and swaps them. Changes like this can interact with some other non NEC practices, in the control panel, often have unexpected results.

 

[mark32]

I would say a short in the coil, the transformer may have had a floating output, but when the wiring was changed, it had one side bonded, now the short drops the control voltage to release the contactor, but is quick enough not to blow the control fuse, if there is one. Just a place to start. Check for voltage from contactor to ground when it is energized, but isolated.

Thanks! I was thinking along those lines, but then thought, isn't the frame of the contactor non conductive?

 

[hillbilly1]

Thanks! I was thinking along those lines, but then thought, isn't the frame of the contactor non conductive?

Depends on the style, Some are all plastic, some have metal back plates, some have metal frames that hold the contactor and overload block. I take it yours is all plastic or phenolic? If it is, then is the wire fairly large and stiff? It may be the pressure on the terminals causing contact loss? But that wouldn’t explain with it working when insulated. Maybe pictures would help.

 

[mark32]

 

[mark32]

Okay, my buddy just sent me these, but I only glanced at them as I'm in the middle of caulking my bathtub for the first time, and I'm finding that it's not a very enjoyable endeavor. Anyway, the shot of just the transformer is the way it was initially wired. The second pic shows the new contactor and the way the transformer is currently wired. In case you are wondering, there is a terminal strip mounted underneath the secondary of the transformer and there is a wire that runs from x3 to the terminal strip, according to my friend.

 

[LarryFine]

Okay, my buddy just sent me these, but I only glanced at them as I'm in the middle of caulking my bathtub for the first time, and I'm finding that it's not a very enjoyable endeavor.

Tip of a teaspoon to press caulk into corners.

 

[mark32]

Tip of a teaspoon to press caulk into corners.

Haha! How did you know that was my beef! I even bought one of those plastic caulk tools, which works well on smaller beads, but it spreads caulk outwards too much, just like a finger, on larger beads, of course. There must be a trick to making straight, even, and "slim" finished caulk lines. Thanks Larry

 

[busman]

Wet finger frequently with water. Don't apply so much caulk that it wants to come around your finger. Clean finger before wetting.

 

[Frank DuVal]

Silicone caulk?

Magic is denatured alcohol instead of water. Saw it in a tile setting video and my daughter says it works great.

 

[retirede]

Haha! How did you know that was my beef! I even bought one of those plastic caulk tools, which works well on smaller beads, but it spreads caulk outwards too much, just like a finger, on larger beads, of course. There must be a trick to making straight, even, and "slim" finished caulk lines. Thanks Larry

First, avoid excessive amounts of caulk.

Most the bead and adjacent surfaces with water before working it. Caulk won’t stick to the wet surfaces. The installers of my granite countertops did this and it turned out really well.

 

[mark32]

Wet finger frequently with water. Don't apply so much caulk that it wants to come around your finger. Clean finger before wetting.

Thank you all for the caulk tips! Unfortunately I didn't start wetting my finger until the end of the project.There was like an 1/8th gap between the first row of tile and the top of the tub, so I had to use a descent amount of caulk to fill that space, and for me it was hard to judge the optimum amount. Maybe I'll post a pic of my handy work

 

[RCC1]

I found the Eaton contactor drawing for that starter. There is a note in the wiring diagram to remove Jumper "C" if you are not using the line voltage for control. I'm assuming you are not using line voltage control, since there is a control transformer mounted there attached to the line side of the starter. The 1, 2, 3 numbering is pretty common for a remote Start/Stop station. The "Stop" button wiring going between control transformer & #2 and the "Start" button wiring on #2 & #3 (that also wires in your seal-in contact). That would leave the "Overload" contact #95 attached to the coil and with #96 going back to the control transformer secondary.

What I can't understand because I don't know where the wires go in the field to the start/stop station, is why is there two wires in the box going to the #3 terminal. Looks like one yellow with orange tape goes out of the box to the field, but the second yellow wire on terminal #3 appears to go back to the control transformer. Why would it be like that? Would make sense if it went to the starter coil A1 terminal at the top.

I'll be curious hear what you find.

 

[mark32]

I found the Eaton contactor drawing for that starter. There is a note in the wiring diagram to remove Jumper "C" if you are not using the line voltage for control. I'm assuming you are not using line voltage control, since there is a control transformer mounted there attached to the line side of the starter. The 1, 2, 3 numbering is pretty common for a remote Start/Stop station. The "Stop" button wiring going between control transformer & #2 and the "Start" button wiring on #2 & #3 (that also wires in your seal-in contact). That would leave the "Overload" contact #95 attached to the coil and with #96 going back to the control transformer secondary.

What I can't understand because I don't know where the wires go in the field to the start/stop station, is why is there two wires in the box going to the #3 terminal. Looks like one yellow with orange tape goes out of the box to the field, but the second yellow wire on terminal #3 appears to go back to the control transformer. Why would it be like that? Would make sense if it went to the starter coil A1 terminal at the top.

I'll be curious hear what you find.

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Hey Bro, thanks for taking the time to investigate this. I have yet to visit the site, but will post what I find. Thanks again!