Coordination Study for PLC Panel

[R_Roc]

I have never been asked to do a coordination study on my PLC Control panel.
I'm using various amperage of the same Allen Bradley Breakers
1489-A1D020 - 2 Amp
1489-A1D030 - 3 Amp
1489-A1D050 - 5 Amp
1489-A1D200 - 20 Amp

These breakers feed power to I/O module,Power Supplies, and various transmitters in the field (Ultra Sonics, Flow Meters, Gas Analyzer).

The Engineer reviewing my Panel Drawings is requesting a coordination study for the breakers and main breaker in my panel that gets power from the distribution panel.

I would believe if a fault (Line-Ground) were to occur the branch circuit breaker that is experiencing the fault would trip first. None of these breakers have adjustable trip curves.

My response for the my Main breaker to the distribution panel would be for the Arc Flash firm who is doing all the calculation on new equipment.

Do these response have a case?

 

[dpc]

It's quite likely that these little breakers will not coordinate well, since all will have instantaneous trip. It will depend on how much short circuit current is available. If you are truly concerned about coordination at this level, fuses are a much better option. If you can maintain a 2:1 ratio of fuse sizes, they should coordinate. Your local Bussmann sales rep will be more than happy to explain.

 

[jraef]

I think first you may want to define what he means by "coordination". In the grand scheme of things, the trip time of a single pole 2A breaker is not generally consequential in a coordination study where the purpose is to ensure that the fault is cleared at the lowest level, nor is this going to be an "Arc Flash" issue at those levels. I'm thinking that what he really wants to see is if those specific breakers are approved for use behind whatever your main breaker feeding this panel is at whatever your Available Fault Current is. Those little IEC style DIN rail mounted breakers come in various formats, some of which are not exactly "kosher" when it comes to using them as Branch Circuit Protective Devices per the National Electric Code here in the US, meaning they MUST have a specific BCPD up stream of them to be used. As it turns out, that specific product line IS UL 489 listed as a BCPD, so it can be used stand-alone in a circuit capable of delivering no more than 10kA fault current, with or without another breaker ahead of it.

Side issue: You are either dealing with an older existing panel, or you are being sold old obsolete products. The 1489A series was supplanted by the 1489M series about 3 years ago. The original A series product is not RoHS compliant, so as of last year cannot be shipped into countries that require it. Because of this, many distributors that failed to return their stock to Rockwell after the change found out that they can't sell them, so they dumped them off onto the "gray market" of breaker brokers who cater to people that buy strictly on price, usually unaware of the possible negative consequences. So if this is new and you have not yet bought the breakers, you may want to change to the 1489M series, unless this is for your own consumption and you are in the US, who does not yet adhere to the RoHS rules. Everything else about them is the same in terms of ratings etc.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[R_Roc]

Coordination to them is ensuring the branch breaker experiencing the fault goes off first before the Main breaker.

Is coordination even necessary at this low level? Typically the circuit breakers are in place to protect the wire/equipment.
Yes this is a new PLC control panel. Even if I switched to the 1489M series breaker will they coordinate well to prevent the Main Breaker from going off?

 

[R_Roc]

@dpc if these breakers are instantaneous trip would not the branch experiencing the fault be the first to trip?

 

[jraef]

What do you mean by a Main Breaker? If it's a 100A 3 phase main and there is a transformer between it and these small loads, not likely an issue. If it's a 40A 1 pole breakers as a Main for all of these, maybe. We can't read your one line from here.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[Paulusgnome]

I find with this question, that it is best to use one of the circuit-breaker trip-curve plotting apps that the various manufacturers have on offer.
I am currently using an application 'Curve Direct' from Schneider Electric, but have used similar software from GE and AB which gives the same results.
In essence, you co-plot the trip curves of the devices that you are wanting to coordinate, and see how they plot in relation to each other.
If you have two curves that are separate and have a reasonable gap between them, then you have some assurance that they will coordinate. If there are zone(s) where the curves intersect of come very close, then you are not so certain.
Knowing just how much separation between curves is reasonable was, at least for me, a matter of asking some of the more experienced engineers for some guidance.

 

[R_Roc]

All the breakers in my control panel have the same manufacturer. Amperage is different. So i ASSUME same trip curve.