Series Rating

[pisani168]

If I have a panel with a remote main disconnect and the panel cbs and the main disconnect are series rated, does the series rating still apply if somebody retrofits a ATS between panelboard and disconnect.

In my opinion the series rating is voided.
What’s your opinion?


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[jim dungar]

I would guess the series rating is still valid, as the closed contacts of the transfer switch are not much different than any other conductor, But I would still check with the breaker manufacturer.

Series rating are typically applied only between two protective device which are effectively in series and there are no other 'devices' which would try to open during the fault. Some series rating are available for more than 2 devices, like a meter center, main breaker, and branch breaker, but not every manufacturer offers them..

 

[iceworm]

Give us some more context.
Q: Is the ats just a switch (no overcurrent protection - no CB, no fuses) that changes the panel feeder from the existing remote main disconnect to a different feeder?

If not, then forget the rest and give us a one-line.

However, if so:
Then when the ats is lined up for the existing main disconnect to feed the panel, then I would expect the existing series rating to still be valid. And when the ats is lined up to feed the panel from a different source, then the series rating isn't valid cause the existing main disconnect is no longer in the circuit.

 

[electrofelon]

I am in the camp that says the transfer switch does not effect the series rating. I admit I am using the "I havent heard about it therefore it doesnt exist" fallacy, however in all my readings on series ratings I have never come across any restrictions on conductors, terminations, switches, etc between the two devices. In fact, according to Eaton, any fully rated breaker may be used in the middle of a series rated pair, so if that doesnt matter, I dont see how a switch would matter. I assume the switch is rated for the ASCC?

 

[pisani168]

I am not able to share a one line since it's classified.

Normal operation:
Switchboard with 100A HJ CB (65kA) - conductor - ATS no CB
Emergency operation:
Generator with 100 HD CB (18kA) - conductor - ATS no CB
Load:
conductor - panelboard - no main principal just EHB CBs

HJ and EHB are series rated
Series rated equipment needs to be labeled as such. I have never heard to labeling series rated equipment for normal operation only. I'd love to rip out the HD, replace it by a HJ and call it a day.

 

[iceworm]

I am not able to share a one line since it's classified.

Interesting. Pen and paper sketch showing interconnection of generic CBs is "classified" - but describing with words is not.

Okay. (Just teasing, not slapping)

I'd love to rip out the HD, replace it by a HJ and call it a day.

You want to replace the gen CB with a higher rated CB, same on as is used for the panel normal feeder?

In NORMAL, feed is a valid series rating. Nothing wrong here. ATS does not matter.

In EMERGENCY, feed is gen to HD (18KA) to Panel EHB (AIC rating unknown) Couple of questions:

What is the AIC rating for the EHB panel CBs?​

What is the available short circuit current of the generator?​

​

Following is pure conjecture on my part:​

The gen CB is likely sized for 1.25 x genFLA. Say 80A. I don't know if the gen is 208V, 480V, 3phase, 1phase. Figuring 480V, 3ph, that is a 50KW (65KVA) generator.​

​

Generators are notoriously light on ASCC. Sub transient reactance Xd" maybe .20 to .25. I would expect the gen short circuit current to be ~ 80/.2 = 400A. Yep, that low.​

So, running on the gen, the question is not, "Can the EHB CB interrupt the Max SCC?"
Rather, "How long will it take the EHB to open with only 400A SCC?"

With the information we have the install appears fine.