series rated vs fully rated

[lectrified]

I need to replace a service to a machine shop. This shop has 3phase 240volt delta. ungrounded. I would like some input on series rated vs fully rated. keep in mind this is only a 200amp service. with an aic rating of 24100. Im also installing a 400amp main with a 200amp rating plug for future upgrade. biggest motor load is 100amps.

 

[augie47]

As far as your gear is concerned, series rating is normally more economical.
At those levels it should not be difficult.
My concern would be more with the withstand rating of the machinery control panles and addressing that.

 

[erickench]

Here's a quote from the IEEE blue book:

Domestic series combinations are also restricted to use in circuits where there is no motor loading on any of the branch circuit breakers.

However, if the total motor HP is less than 50 then the fault current contributions should not be considered. But you have a machine shop. What is the total HP of all the motors? Also, series ratings cannot be applied if motors, or other equipment that contributes to a short-circuit current, are connected between the line-side MCCB or other device and the load-side MCCB.

 

[CEDTOM]

lectrified,
In my opinion, you need to look for series ratings at 400 Amp @ 240V since that is the C/B frame size you will be using. Your first step is to identify the manufacturer of the branch circuit panels & C/B's. If they are all of the same manufacturer, then you may be able to find a series rating with those C/B's and a 400A Frame C/B of the same manufacturer. If the panels are of different manufacturers, then getting a series rated system will be pretty difficult.

As far as your motor loads are concerned, larger motors can contribute to a larger fault that the utilities contribution will be. In other words, if the utility gave you the 24,100A fault level, then you motor contribution could make that number higher.

Most US C/B manufacturers have series ratings for 400A C/B's at 240V starting at 22k. The next levels are maybe 25k, then 42k & 65k. It's OK to go higher than the value you need, it just costs more.

 

[jim dungar]

Actually, motors are allowed as long as their FLA is then 10% of the AIC ratings of the lower rated device. So, for a 10kAIC breaker you would be allowed to have 100A of motor load. It is unlikely that a 200/225A branch circuit panel would have 100A of motor loading.