What is the maximum load for an AP8941

[BillP]

Hi,

The AP8941 is listed on the APC website as "Rack PDU 2G, Switched, ZeroU, 30A, 200/208V, (21) C13 & (3) C19"

However, when you log in to the device it has a rating of 24A.

Does anyone know what rating the two breakers are on the PDU and whether it is safe to push the loaf up to 30A?

Thanks,

Glenn

[BillP · Accepted solution]

Hello,

The AP8941 is a 30A unit, meaning it has a 30A plug on it. Its rating is 80% of that (for the USA) which is 24A. I believe it has two banks on it with a maximum rating of 20A, with a rating of 16A. This PDU should have a 30A breaker feeding it and will trip at 30A. The bank breakers will actually trip at 20A since that is their max rating.

Depending on the region though, they might not go by the 80% rule that we have here in the USA with National Electrical Code which we have here for UPS, but it applies to PDU too -> Why is my APC by Schneider Electric UPS derated to 80% of the circuit's total capacity? | FAQs | Sch...

With all of that said, since all regions don't go by this 80% rule, what they did is put the 20A banks with a threshold range from 0-22A so that users could disable it ultimately if they wanted and a little bit to account for some slight inaccuracy measurement scenarios.

Technically, you should not load this PDU over 24A total, or 16A for each bank and if you do, it should not last for more than 3 hours. Anything that runs over 3 hours should be sized per 80% rule and ultimately, you should have larger than a 30A breaker feeding the PDU. All of the internal components are rated for 30A though.

Here is some information i have saved from our compliance team on the topic:

First, let me state that as far as rack PDUs are concerned, there is no such thing as "UL derating." While a product may have a 30 amp plug and 30 amp circuit breakers, the product rating is 24 A - period. There is no allowance for exceeding this current.

Any concept of derating in the US and Canada comes from the US NEC and the Canadian CEC, stating that a circuit breaker cannot be loaded to more that 80% of its rating for continuous loads. By definition, IT equipment is considered a continuous load. Below from the UL requirements for circuit breakers.  

"Unless otherwise marked, circuit breakers should not be loaded to exceed 80% of their current rating, where in normal operation the load will continue for three hours or more."

They are going to change the breaker thresholds again because of confusion users have had and my own original confusion too. AP8941 happens to be sold in multiple regions like NAM and Japan.

Hope this helps. Let me know if you have other questions.

[BillP]

That's very helpful! Thank you Angela