Overloaded my UPS (Sorry, don't know where else to put this)

[Fritz]

I had 4 SM SC846 servers plugged into a APC 1500va UPS. I rarely have more than one running at a time but this morning I had need to have all 4 running. About 5 minutes after firing up the last one the whole rack went dead. The UPS showed overload. I then plugged 3 of them into the wall and plugged the FreeNAS box into the UPS alone. It runs 24/7 so this made sense.

Anyway, I always thought that if you overloaded a UPS it just wouldn't carry the load in the event of a power failure. But you wouldn't know it was overloaded unless the power went out. Apparently this isn't the case. Are all UPS like this?

 

[andrewbedia]

All of the ones I've used are like this.

 

[T_Minus]

You can't draw more than a circuit breaker is rated for and the same is true for a UPS unit.

You can't draw more power than the unit is rated for delivery as long as the unit is 'smart' and doesn't allow it, which they should not allow.

An extension cord is an example of a 'dumb' device that you CAN draw more than it's rated for however eventually it will over heat, short and/or melt and catch on fire... you don't want this to happen to a UPS or your rack so the 'smart' systems will prevent this and turn off/disable the load completely.

 

[Fritz]

circuit breaker didn't pop, the UPS did.

 

[Fritz]

All of the ones I've used are like this.

Yep, that's what I figured.

 

[Diavuno]

I also have a smart 1500 for my 846 machine.

I'm pretty sure they do this for a few reasons.

first, the device is rated at x load, if you exceeded that load and it caught fire who is responsible?

second, is a plain safety measure.

and 3rd, I'm pretty sure on these guys they take power in, it hits the batteries and then it pulls from the batteries to the outlets on the unit. it's a type of conditioning that the unit can only support up to x load.

 

[Blinky 42]

If it is one of the Online SmartUPS's then it does full conversion all the time - AC in to DC to AC back out, so you can't exceed the design capacity of any of the stages.

 

[Fritz]

Not sure if it's an online UPS or not but I definitely see the safetry side of it. Hitting the batteries with a humongous load can indeed cause an explosion. I witnessed this first hand with a Cyberpower UPS years ago. It sent shrapnel all over the office and scared the bejeebus out of everyone.

The UPS returned to normal operation after powering it off and back on again so the protection circuitry did it's job.

 

[T_Minus]

circuit breaker didn't pop, the UPS did.

Please re-read my post I never said your circuit breaker did, I used it as an example of another type of device that 'stops' the flow of electricity at a certain level, and your UPS does the same, an extension cord DOES NOT, etc...

You want it to not overload itself, catch fire and/or damage other equipment.

It's a good thing it stopped working and did not run 'overloaded'

It really has nothing to do with "hitting the battery" with a load it's about drawing more through the wires than they're rated for, about drawing more through the rest of the circuits than it's rated for, the battery exploding and over loading is a 2ndary problem, the over load on the lines + heat + fire may occur well before the UPS used/needed batteries at all.

 

[Fritz]

It's nice to know that the UPS will indeed shut down before a meltdown or equipment damage occurs. Not cool discovering this by accident but it is nice to know.

 

[Diavuno]

Hitting the batteries with a humongous load can indeed cause an explosion. I witnessed this first hand with a Cyberpower UPS years ago. It sent shrapnel all over the office/QUOTE]

Note to self, keep on avoiding cyber power in favor of APC