I recently got back from the Las Vegas AFCOM conference. One of the thing the power vendors hit hard regarding power strips was the acceptance of using fuses rather than breakers. Their argument was that breakers will break at various loads, not necessarily at 15amps; fuses always break at a rated load.
I have put in about 30 strips of breaker-based power strips (APC 7841) and am now wondering if I've made a mistake.
There is a big debate going on now mostly between Server Technology, who manufacture rack PDUs with fuses, and Pulizzi Engineering, who use magnetic breakers. I think there are pros and cons to both sides. Customers will make up their own minds.
To change a fuse, a user has to expose themselves to hot contacts for the fuse. Some power strips I've seen have a very light piece of clear plastic covering the 208 VAC 30 amp fuse which you get to by pulling the cover and then you've got a hot contact and a grounded contact. Seems like a good way to get burned.
My preference is a breaker which can be reset or better yet, locked off if you need to with a lockout kit. Fuses are good for bigger loads which code requires (motors) but breakers are my preference.
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CNN Internet Technologies
Data Center Manager
To change a fuse, a user has to expose themselves to hot contacts for the fuse. Some power strips I've seen have a very light piece of clear plastic covering the 208 VAC 30 amp fuse which you get to by pulling the cover and then you've got a hot contact and a grounded contact. Seems like a good way to get burned.
My preference is a breaker which can be reset or better yet, locked off if you need to with a lockout kit. Fuses are good for bigger loads which code requires (motors) but breakers are my preference.
At the conference, Server Tech had a redesigned power strip that you pull/rotated the fuse holder out to change it. The closest I can describe it is in the movie "The 5th Element" where towards the end a Jamacan was changing out the fuel cartridges...or in some kitchens there are drawers that pivot on the bottom and you pull out the bin from under the counter. I would be willing to use one of those systems.
At the conference, Server Tech had a redesigned power strip that you pull/rotated the fuse holder out to change it. The closest I can describe it is in the movie "The 5th Element" where towards the end a Jamacan was changing out the fuel cartridges...or in some kitchens there are drawers that pivot on the bottom and you pull out the bin from under the counter. I would be willing to use one of those systems.
That's an infinitely better method. However, to inspect such a fuse, you have to pull it to check, which breaks the contact. If for some reason you're confused on which fuse you need to pull to replace, you could be pulling the wrong fuse and loosing more outlets on a given (or separate PDU). From an ease of use standpoint, breakers are easier because they typically fail to a center position (unless they fail entirely in a non standard mode) in which case a fuse would have probably done something similarly spectacular. I've seen the old screw in type fuses blow the door off a distribution panel and throw fragments of glass across a garage, so with power, some things are just pear-shaped no matter what when you have an overload condition.
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CNN Internet Technologies
Data Center Manager
The debate of whether or not to use a fuse of a circuit breaker is kind of unsettling in a forum such as this. A properly ran datacenter should have capacity planning methods put in place to mitigate the risk of overloading a circuit. You should never exceed 80% capacity on a circuit. With running circuits at 80%, you should not have an issue with overloading a circuit unless someone were to plug in a massive shop vac in to your power strip to do some cleanup; in which case, a circuit breaker would be ideal because you would want to just be able to hit the reset button on the strip instead of replace a fuse.
In all my years of running datacenters, I have only ever had 1 breaker trip and that was because a plug was part of the way out on a vertically mounted PDU strip and a contractor accidentally touched the exposed part of the plug with a screw driver. A simple flip of the breaker and all was good again.
The debate of whether or not to use a fuse of a circuit breaker is kind of unsettling in a forum such as this. A properly ran datacenter should have capacity planning methods put in place to mitigate the risk of overloading a circuit. You should never exceed 80% capacity on a circuit. With running circuits at 80%, you should not have an issue with overloading a circuit unless someone were to plug in a massive shop vac in to your power strip to do some cleanup; in which case, a circuit breaker would be ideal because you would want to just be able to hit the reset button on the strip instead of replace a fuse.
In all my years of running datacenters, I have only ever had 1 breaker trip and that was because a plug was part of the way out on a vertically mounted PDU strip and a contractor accidentally touched the exposed part of the plug with a screw driver. A simple flip of the breaker and all was good again.
Just my $.02
I totally agree. Each strip gets 30 amps, de-rated to 24amps...then split it in half for redundancy, which is now 12amps. That should be the limit. However, I do have a few at 13 - 14 amps. Even with that loading and have one strip fail for some reason...I *shouldn't* have problems...but shouldn't doesn't mean won't.
My concern with deciding which way is best...is just that. Which way is best? Since I posted, I've been talking to my vendors who have been talking to their manufacturers...it goes either way. From what I heard here and other places, I won't have any worries buying either.
EDIT: We have a separate circuit for equipment not normally found in data centers. A shop vac would never get plugged into a rack.
I´m building a new data room, 500 machines average capacity at full load, i find easy to design a setup with two independent circuits to each rack, each circuit have a breaker, every rack row have 2 independent master breakers. In the case we have a broken power supply in a server, it can make the breaker act, so the second circuit can serve any secondary power supply in the rack. Even in the case a master breaker act, the secondary master will still provice power to the secondary set of circuits. At the end we have a couple of ups.
These is a costly setup, but we deploy it just on the critical rack rows, routing, switching and premium customers only. N+1 for the critical stuff and a very isolating electrical scene for the rest.
In the past i have power issues due power supply failitures inside ups protected circuits, when something like that happens, some times you have a complete rack or row down as certain power supplys can blow and make breakers act.
I don´t know what you think about my strategy, sounds good in theory, i will complete these scene in the next 2 weeks. any commens welcome !
I find these forum very insteresting, thank again!
Power strip overload protection
