MCC Combination Starter Bucket Question

[Designer69]

(A) I have an existing 15 HP fan that will be replaced by a 5 HP fan.

also

(B) I have an existing 1 HP fan that will be replaced by a 5 HP fan.

Separate MCC Buckets for these.

Can I keep the existing Breaker in the bucket and just replace the starter for A? (existing is FVNR, new needs RVNR)

For (B) the entire bucket should be replaced right?


Thank You

 

[drktmplr12]

(A) I have an existing 15 HP fan that will be replaced by a 5 HP fan.

also

(B) I have an existing 1 HP fan that will be replaced by a 5 HP fan.

Separate MCC Buckets for these.

Can I keep the existing Breaker in the bucket and just replace the starter for A? (existing is FVNR, new needs RVNR)

For (B) the entire bucket should be replaced right?


Thank You

you do not need to replace the starter. having it oversized will cause no issues.

you WILL need to replace the heater units based on the NAMEPLATE amps of the new motors. this is because the circuit breaker in MCC buckets are typically motor circuti protectors (magnetic trip only) and will respond only to a short circuit. the heaters provide overload (small overcurrent for long time period) protection. all motor circuits require both short circuit and overload protection. refer to Article 430

https://www.mikeholt.com/mojonewsar...s-Motor-Circuits-and-Controllers~20031126.htm

 

[Jraef]

Chances are that those buckets were built with MCP (mag-only) breakers and the settings may not work for the new motors.

 

[Designer69]

Thank you for your help guys.

Where are the heaters typically located , right in the bucket?

Are these easy to replace as far as space etc.?

 

[Designer69]

Looks like the heaters are part of the starter. You just unscrew the existing heater elements and put new ones in.

Simple as that right?

Thanks

 

[drktmplr12]

Thank you for your help guys.

Where are the heaters typically located , right in the bucket?

Are these easy to replace as far as space etc.?

Video from SQD on replacing thermal units: https://www.youtube.com/watch?v=Gy1KrKzer3o&vl=en

 

[Jraef]

Looks like the heaters are part of the starter. You just unscrew the existing heater elements and put new ones in.

Simple as that right?

Thanks

As far as changing the heater elements, yes.

On your 15HP stater, that would be a NEMA Size 2 starter, a 5HP only needs a NEMA Size 0, although some MCC mfrs don't go below Size 1. But irregardless, you can always run a smaller motor on a larger starter, so the contactor size is fine. But when you go to select the proper heaters, you must look on a chart for a SIZE 2 starter for the value of the heater elements you need, they might be different than those used on a Size 1 or Size 0 starter.

On the other one, you have a 1HP now and want to go to 5HP, either way it will be a Size 0 (or Size1) starter, so no problem selecting the heaters from the same chart.

BUT...

As I said, the breakers are going be a problem. For example the MCP used on a 15HP starter would probably be rated for 50A continuous with the mag trips adjustable from 150 to 500A. When you go to use that for a 5HP motor with an FLC of 7.6A. the HIGHEST setting you might be allowed to use on an MCP for a standard motor would be 83.6A, so the LOWEST setting on the MCP would be almost twice the allowable setting. Even if your motor is an "energy efficient" design and you can use the NEC exception that allows 1700% as the setting, that's still only 129A, still not close to the lowest possible setting of that breaker. It can't work.

On the 1HP starter, the MCP is likely rated 7A, with an adjustment range of 21 to 70A, and on a 5HP motor you can use the 70A setting, but it might nuisance trip on you.

 

[petersonra]

Where I used to work I don't recall ever using MCPs. It was always MCCBs. This was because AB charged us more for an MCP than for an MCCB in MCCs.

We also supplied a lot of combination starters. Most of them were fused. It was a popular option with a lot of our customers at the time.

 

[Jraef]

Where I used to work I don't recall ever using MCPs. It was always MCCBs. This was because AB charged us more for an MCP than for an MCCB in MCCs.

We also supplied a lot of combination starters. Most of them were fused. It was a popular option with a lot of our customers at the time.

Huh. Well, technically an MCP (Motor Circuit Protector) IS an MCCB (Molded Case Circuit Breaker), it's just a Mag-Only MCCB, as opposed to a Thermal-Mag MCCB. Maybe we are missing on the terminologies? I'm using MCP as the old Westinghouse Motor Circuit Protector term, which is now generic. Maybe you are thinking of the MPCB, Motor Protection Circuit Breaker, which is an MCCB that has adjustable thermal trips that can act as the OL relay, so per UL can ONLY be used in motor starter circuits. Those are used a lot in Europe, where THEY sometimes call them "MCPs", but those are not used much here where people are used to separate OL Relays.

Other than for a brief time a couple of years ago, the only option for A-B circuit breaker starter buckets was MCPs. When they changed breaker designs, the 7A MCPs took too long in UL, so they used 15A T-M breakers for about 6 months on small starters. Possibly at that time if you insisted on an MCP for a small starter, they may have had to use the old Eaton breakers, and when A-B released their own breakers, Eaton cut them off immediately, so they had to buy Eaton MCPs from distributors instead of direct. That would have reflected in the price.

 

[petersonra]

Huh. Well, technically an MCP (Motor Circuit Protector) IS an MCCB (Molded Case Circuit Breaker), it's just a Mag-Only MCCB, as opposed to a Thermal-Mag MCCB. Maybe we are missing on the terminologies? I'm using MCP as the old Westinghouse Motor Circuit Protector term, which is now generic. Maybe you are thinking of the MPCB, Motor Protection Circuit Breaker, which is an MCCB that has adjustable thermal trips that can act as the OL relay, so per UL can ONLY be used in motor starter circuits. Those are used a lot in Europe, where THEY sometimes call them "MCPs", but those are not used much here where people are used to separate OL Relays.

Other than for a brief time a couple of years ago, the only option for A-B circuit breaker starter buckets was MCPs. When they changed breaker designs, the 7A MCPs took too long in UL, so they used 15A T-M breakers for about 6 months on small starters. Possibly at that time if you insisted on an MCP for a small starter, they may have had to use the old Eaton breakers, and when A-B released their own breakers, Eaton cut them off immediately, so they had to buy Eaton MCPs from distributors instead of direct. That would have reflected in the price.

That was relatively recent. I remember when eaton told them to go to ****.

Where I used to work was 30 some years ago and AB was not pushing MCPs at all in their MCCs. You could get them but they charged us extra for them. Of course they charged us less for silver plated bus over standard tin plated bus, so they had some really strange pricing practices back then. I don't recall the exact split but I would guess at least half our customers wanted fused disconnects in the buckets instead of MCCBs. IIRC, there was not much difference in price between a bucket with an MCCB and one that had a fused disconnect.

On a somewhat humorous note, we learned over time that AB came very close to pricing their MCCs by the section, at least to us. It did not much matter what was in a section, it came out to about the same price per section. If we could not get a price from AB quick enough we would just estimate the cost based on how many sections the MCC would need.

I seem to recall that if you wanted green "run" lights instead of red ones it was like a $100 per bucket adder. So we used to just buy the standard color lights and replace the lens for our customers that wanted green "run" lights.

 

[Jraef]

That was relatively recent. I remember when eaton told them to go to ****.

Where I used to work was 30 some years ago and AB was not pushing MCPs at all in their MCCs. You could get them but they charged us extra for them. Of course they charged us less for silver plated bus over standard tin plated bus, so they had some really strange pricing practices back then. I don't recall the exact split but I would guess at least half our customers wanted fused disconnects in the buckets instead of MCCBs. IIRC, there was not much difference in price between a bucket with an MCCB and one that had a fused disconnect.

On a somewhat humorous note, we learned over time that AB came very close to pricing their MCCs by the section, at least to us. It did not much matter what was in a section, it came out to about the same price per section. If we could not get a price from AB quick enough we would just estimate the cost based on how many sections the MCC would need.

I seem to recall that if you wanted green "run" lights instead of red ones it was like a $100 per bucket adder. So we used to just buy the standard color lights and replace the lens for our customers that wanted green "run" lights.

I was part of that “price per section” crowd back then when I was an MCC specialist for an AB distributor and then later for another mfr.. I kept records of all of my successful bids and noticed that if I quoted at $2,000 per section I won, $2200 and I lost, $1800 and the factory would reject the order. Didn’t matter what was in it, it was $2,000 per section. That formula held for around 7 years through the late 70s to mid 80s, unchanged. Then I got out of the MCC business and when I came back in, VFDs and Soft Starters had made their way into MCCs and it all changed.

I also remember red vs green pilot light issue, it was a bugaboo for a long time in the days with manual paper configurators, because they used standard pre-printed diagrams for assembly and if you changed, someone had to manually create new drawings. It wasn’t until software based configuration and CAD drawing systems cane along that they allowed more flexibility.

 

[paulengr]

In the 1/5 HP case it depends on the MCP adjustment range or MCCB size, the starter size, and wiring. For instance with a 00 starter going to 5 HP won't work. At size 1 or larger it might. Many manufacturers have a minimum size of 1 or 2 because the frame and cost are the same so keeping inventory of size 0 and 00 is more expensive.


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