Motor starter / contactor troubleshooting

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pipelinetech

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Hi guys,

I searched through the forums and could not find anyone else who has asked this question.

I have a disconnect on a pump that houses a 240v breaker and 2 Allen-Bradley C23-D10 starters to control 2 separate pumps. There are 2 HOA switches on the front of the disconnect that control the 2 different 120v contactors. I had an extra conductor in the cable that was installed, so I landed the extra on a neutral bar in our electrical room.

In the disconnect, there is a fused terminal block that needed 120v to run the HOA switches and the starters. I came off the load side of one of the legs of the 240v breaker to power it.

When I switch the HOA switch to the "hand" position, the contactor on the starter hammers- it will rapidly move the electromagnet in-out-in-out until finally sticking in after a few seconds. It releases just fine when the 120v is taken away.

I am at my wits end on what could be causing this: does anyone here have any insight or encountered anything similar?

Thanks!
 
You may want to check the 'Leg" you have chosen to ensure it is 120volt to ground.

Next, what is the HP of the motors you are starting? Do they both start at the same time? What size of wire are you using to feed these motors? Is this a new install?

Excessive voltage drop can cause your problem and while it could and may be a compromised neutral as suggested, check your install.
 
pipelinetech said:
Hi guys,

I searched through the forums and could not find anyone else who has asked this question.

I have a disconnect on a pump that houses a 240v breaker and 2 Allen-Bradley C23-D10 starters to control 2 separate pumps. There are 2 HOA switches on the front of the disconnect that control the 2 different 120v contactors. I had an extra conductor in the cable that was installed, so I landed the extra on a neutral bar in our electrical room.

In the disconnect, there is a fused terminal block that needed 120v to run the HOA switches and the starters. I came off the load side of one of the legs of the 240v breaker to power it.

When I switch the HOA switch to the "hand" position, the contactor on the starter hammers- it will rapidly move the electromagnet in-out-in-out until finally sticking in after a few seconds. It releases just fine when the 120v is taken away.

I am at my wits end on what could be causing this: does anyone here have any insight or encountered anything similar?

Thanks!
Click to expand...
Let's back up a bit and start with this; is your service 3 phase or single phase?
 
Jraef said:
Let's back up a bit and start with this; is your service 3 phase or single phase?
Click to expand...


The service is 120/240v, and I have 240v between the two legs of both the line and load side of the breaker installed in the service disconnect. I had a spare conductor in the cable that I landed on the nuetral bar in our electrical room. From line 1 to ground and line 1 to nuetral I was reading 119.8v.
 
ptonsparky said:
You may want to check the 'Leg" you have chosen to ensure it is 120volt to ground.

Next, what is the HP of the motors you are starting? Do they both start at the same time? What size of wire are you using to feed these motors? Is this a new install?

Excessive voltage drop can cause your problem and while it could and may be a compromised neutral as suggested, check your install.
Click to expand...

Yes, it's a new install. The motors are 1/2 hp, 240v / 6amp, and the plan is to run only one at a time but both are being fed by the same breaker and the hoa switch is controlling which one will be active. They are being fed by 10ga thhn, about 350' away from the transformer.
 
You need to engage the services of a qualified electrician.

That said, I am closing this thread, in accordance with the Forum rules. This Forum is intended to assist professional electricians, inspectors, engineers, and other members of the electrical industry in the performance of their job-related tasks. However, if you are not an electrician or an electrical contractor, then we are not permitted to help you perform your own electrical installation work.


If I have misjudged the situation, if for example this project is related to your work, then send me a Private Message. If you can show me that I am wrong, and that you are a licensed electrician (or at least a licensed apprentice), then I will reopen your post, and offer an apology for the delay and inconvenience.

A reminder to all members, if you see a questionable post, feel free to report it by clicking the
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I have re-opened this because the OP has shown me that he is an EC. Just a word to the wise, what you say in your profile matters...

You provided a photo of the panel (I'll let you decide if you want to post it or not). In there I see a potential issue in the control circuit and 2 definite problems with the power circuit.

1) The potential control issue is that your Neutral for the control circuit is landed on terminals labeled "X2", which is fine, but then elsewhere I see several other white wires, obviously USED in the neutral circuit because they go to the Neutral sides of coils, but with DIFFERENT wire numbers on them; namely wire #8 and wire #11. Conventional wisdom is that all Neutral wires should be the same number because they are all common to the same circuit. In this case the different numbers imply they are being switched, hence the circuit change, and that is a potential problem all by itself. Then wire #11 is on the terminal strip labeled "remote", which implies it is leaving the panel to go to a remote device of some sort. GENERALLY, remote devices in something with an HOA switch are just contact closures. If you have a Neutral circuit leaving the panel or coming back from somewhere else, and it is getting tied to a Neutral in some other panel, you could be creating some sort of weird grounded loop. Hard to say any more than that though, I would need to see a schematic. Is there one?

2) The first DEFINITE power problem is that this is apparently a single phase panel and motors. When you use IEC starters like those, the OL relay MUST have current flowing through all three sensors, otherwise it will nuisance trip. The instructions that came with it would have shown you how to deal with that on a single phase circuit. You loop one phase back through in series with another so that all three OL sensors see current, even though two of them see the SAME current. Your photo shows that you didn't do that.

3) The second power problem is that the Sq. D PowerPact circuit breaker that you used ahead of the two starters is an MCP, meaning it is a Magnetic-Only circuit breaker, or what the NEC refers to as an I-T (Instantaneous Trip) breaker. That is illegal in this application, you must use a Thermal-Magnetic (aka "inverse-time/current") circuit breaker. The ONLY people who can legally apply an MCP to a motor controller are the manufacturers of the starters, and I guarantee that A-B has not listed their starters with a Schneider MCP breaker.

4) Then legally you must have separate short circuit protection for each motor, you have one breaker feeding two separate motor starters. So you need TWO breakers. This is not causing the problems you are seeing, but it is not code compliant.
 
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