- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
It's is simply a grounded conductor. It is treated just like the typical neutral you are used to, in fact it should even be white of gray.
MCB to turn AC motors on and off.
- Thread starter grotor
- Start date
- Occupation
- Licensed Electrician
It's three phase delta with a "neutral" but without a fourth wire. When you put your meter B to ground you get 0V instead of 480V.
See post 10. He doesn’t care about anything that might be amiss. He only wants to know how long his breaker will last using it to switch both motors!
- Location
- Tennessee NEC:2017
- Occupation
- Semi-Retired Electrician
So does it land on the neutral bar?
- Occupation
- Licensed Electrician
Yes. It is a grounded conductor just like a neutral conductor is a grounded conductor.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
This is what motor starters are made for, they are typically designed for at least 1,000,000 electrical operations, as opposed to the 6,000 of a circuit breaker. Makes no sense that they use the breaker AS a motor starter, when they HAVE a motor starter!
Someone is being lazy. What’s the point of asking how long they can get away with this laziness? Just let them suffer the consequences, maybe it will foster a change in their behavior…
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
It is the grounded conductor, it must be bonded at the service equipment or either the source or first disconnect if separately derived system. You treat it exactly like you do a grounded neutral on most any other system.
Sorry I see there were more posts that covered this. I happened to be right at page break before replying.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Isn't NEMA contactors typically million operations and IEC typically 500k in their specifications?
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Since OP has motor starters, the breaker in question is breaking the load when he turns it off. Unless the control voltage comes from elsewhere the breaker isn't exactly closing into a motor trying to start as it would first be energizing the contactor coil and the contactor would be taking the beating of closing under motor starting current.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
No, especially if they are both tested to UL standards.
The difference between IEC and NEMA is the amount of load each is rated for. For example a NEMA Size 1 starter is actually rated for 27A, quite a bit more than a standard10HP 480V motor so it lasts forever, compared to a 10HP IEC that is rated for only 15A. If you used a 30A IEC it would last as long as the NEMA.
The cheap stuff is the Definite Pupose contactors.
Deltaforce
Member
- Location
- India
- Occupation
- Electrical Engineer
Avoid nuisance tripping on start current !?See post 10. He doesn’t care about anything that might be amiss. He only wants to know how long his breaker will last using it to switch both motors!
You didn’t read post 10.
Deltaforce
Member
- Location
- India
- Occupation
- Electrical Engineer
I try find reason for excessive size mcb regard to 3 hp motor Assuming op aware code maximum size, reason for beyond that size may be use Q0 square d mcb it not meeting code maximum size nuisance tripping otherwise.
Deltaforce
Member
- Location
- India
- Occupation
- Electrical Engineer
Sorry error reasoning.
Deltaforce
Member
- Location
- India
- Occupation
- Electrical Engineer
But iit is feeder breaket 30A. not branch breaker for 3hp motor
If there’s no downstream OCPD, it’s a branch circuit. Just because it supplies 2 motors doesn’t make it a feeder.
Deltaforce
Member
- Location
- India
- Occupation
- Electrical Engineer
Overload relay for motor op#4, overload relay ocpd
That’s not how it works.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Overload relays are not standalone branch circuit OCPD.
The OP refers to individual disconnects but does not say if they contain OCPD. Based on the supplied information it appears the QO breaker is the OCPD for both motors.