Starter Removal

A

Alwayslearningelec

Senior Member
Location
NJ
Occupation
Estimator
These are 100A and 200A circuits. As you can see the circuit is staying place and reconnected after motor replaced. There are now VFD's at the motor, so I guess that's why the starter is being removed.

1. Is it a hard process to remove starter from MCC?
2. Guess wiring in MCC has to be relanded somewhere in the MCC or modified since the starter is being removed?

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It shouldn't be an issue, power can be isolated at the mcc bucket where the starter resides, and the starter isn't hard to remove. I would look into what exactly is expected to happen with the control wiring.
 
Ken_S said:
It shouldn't be an issue, power can be isolated at the mcc bucket where the starter resides, and the starter isn't hard to remove. I would look into what exactly is expected to happen with the control wiring.
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Thank you . For MCC control wiring where is it usually run? From MCC to the motor? Would each power circuit from MCC also have control circuit/wiring? I'd like to send an RFI to the GC. Thanks
 
Assuming that you are planning to use the breaker in the MCC as the OCPD for the circuit, you need to verify that it is a thermal magnetic breaker. Some MCCs use motor circuit protectors that look like breakers but that cannot be used to provide overcurrent protection for remote equipment.
 
don_resqcapt19 said:
Assuming that you are planning to use the breaker in the MCC as the OCPD for the circuit, you need to verify that it is a thermal magnetic breaker. Some MCCs use motor circuit protectors that look like breakers but that cannot be used to provide overcurrent protection for remote equipment.
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The MCC is existing and current feeding motor loads. Those motors are being replaced and feed with existing circuits. So with that in mind I wouldn't need to inquire about what you mentioned?
 
Alwayslearningelec said:
The MCC is existing and current feeding motor loads. Those motors are being replaced and feed with existing circuits. So with that in mind I wouldn't need to inquire about what you mentioned?
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Yes you need to know. A combination starter can use a motor circuit protector, also known as an instantaneous only, or magnetic only breaker. It can only be used a part of a listed combination starter.
You cannot not use that type of device to protect any other type of equipment such as a VFD.
 
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IMO someone would definitely need to confirm the existing OCOvices are compatible with the new equipment
 
As Don stated you are definitely going to need to verify the circuit breaker. I know on our mccs the older ones almost always had motor circuit protector breakers.

Regards to the control wiring, I guess you need to verify your scope of work if is to include the control wiring. I would hope there's an engineered drawing for that work detailing what needs to go where.
 
Yes, what Don mentioned is correct. You need to make sure the breakers are thermal magnetic and not instantaneous trip.

The control wires come from the controls that start the motor to the MCC. They need to go from the controls that start the motor to the VFD. (maybe they are installing a new control system)

The existing motor power wires from the starter load side get rerouted to the load side of the VFD. The VFD then is powered from the existing MCC breaker if it is the correct size and type.
 
I read a study on MCC safety one that claimed that more than half of all industrial accidents involving MCCs were from people pulling buckets out live. Unless it is a relatively new MCC with the ability to disconnect the starter bucket bus stabs from the outside before opening the unit door, you had better consult with the building owner regarding your needing to power down the entire MCC to remove starter buckets. The buckets (units) have "stabs" that connect to the MCC power bus in the sections, and the stabs often get difficult to remove with age. Then they break off, short against the steel stricture and it can all blow up in your face! If the MCC must remain live, you must suit up to the established PPE levels for the incident energy, then go through a "hot work permit" process with the owners, with them understanding the significant risks involved and signing off on it.
Lots of seasoned electricians are going to want to argue this point, based on "I've done it that way for years", but OSHA is very clear on this issue and how hot work in general is required to be conducted. Ignorance is no excuse either.
 
Another thing to consider if you need to replace the circuit breaker in the MCC, is you're going to want to confirm that the new circuit breaker will fit properly in the bucket. So, you're going to want to get the data off the MCC nameplate for the supplier to cross reference.
 
Jraef said:
I read a study on MCC safety one that claimed that more than half of all industrial accidents involving MCCs were from people pulling buckets out live. Unless it is a relatively new MCC with the ability to disconnect the starter bucket bus stabs from the outside before opening the unit door, you had better consult with the building owner regarding your needing to power down the entire MCC to remove starter buckets. The buckets (units) have "stabs" that connect to the MCC power bus in the sections, and the stabs often get difficult to remove with age. Then they break off, short against the steel stricture and it can all blow up in your face! If the MCC must remain live, you must suit up to the established PPE levels for the incident energy, then go through a "hot work permit" process with the owners, with them understanding the significant risks involved and signing off on it.
Lots of seasoned electricians are going to want to argue this point, based on "I've done it that way for years", but OSHA is very clear on this issue and how hot work in general is required to be conducted. Ignorance is no excuse either.
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Yep, we did that for a long time and never had an incident, but it was one of the riskiest things we did.
About 30 years ago, the plant electrical safety people said that the MCC bus must be shutdown to remove or install a bucket.
 
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