Undervoltage trip breakers.

[steve66]

A UPS for a server room needs replaced. In order to accomplish this, I think we will have to put some of the computer room servers on normal power while the UPS is being changed out.

Problem: If the normal power does go out (which we are really hoping doesn't happen), we don't want the servers to automatically restart when the power comes back on. (IT tells me the restart is worse than having a the computers shutdown unexpected.)

I'm thinking of spec'inig breakers with a UNDERVOLTAGE TRIP to feed the servers from normal power. My thought is that if the power goes out, the breaker will open, and the servers won't restart until someone resets the breaker.

New breakers have to be installed to feed the servers with normal power anyway.

Good idea? Bad idea?

I'm a little worried that the undervoltage feature might trip on a small glitch in the power.

Steve

 

[K8MHZ]

How about some sort of contactor?

Those can be arranged to stay open when the voltage drops.

 

[Jraef]

How about some sort of contactor?

Those can be arranged to stay open when the voltage drops.

I agree. If it's temporary, I would do it with electrically held contactors. You can get them with 24VDC coils and use a 24VDC power supply to operate them which has a Ride-Through module attached that keeps the coil voltage up for a few extra seconds if it's just a short power glitch. I use these all the time on semiconductor tooling systems where they have a ride-through spec for similar reasons. A 2 or 3 second dip or hiccup can cost them hundreds of thousands of dollars in lost product, safe shutdown procedures and lengthy restarts.

 

[steve66]

Thanks for the suggestions. I had thought about using a contactor also. I'm just not sure the extra expense and effort for the contactor is justified.

It will be (2) 200 amp panels, so the contractors would have to be pretty large. And with any luck, this will only be needed for a couple of days.

Steve

 

[augie47]

If I understand correctly I see a potential problem. If the normal power fails at any time the breakers would open. If that occurred today, two weeks from now if they needed to switch to normal power the breaker would still be off... would that create a problem ?
(or are you going to change them back out)

 

[steve66]

If I understand correctly I see a potential problem. If the normal power fails at any time the breakers would open. If that occurred today, two weeks from now if they needed to switch to normal power the breaker would still be off... would that create a problem ?
(or are you going to change them back out)

When the new UPS is installed, the panels will be reconnected to the UPS, and the two breakers with undervoltage trip would remain as spares.

Steve

 

[eric9822]

I'm a little worried that the undervoltage feature might trip on a small glitch in the power.

Steve

They will. I removed the ones we had in our data center because they were causing more problems then they solved.

 

[steve66]

They will. I removed the ones we had in our data center because they were causing more problems then they solved.

Thanks, thats good to know.

 

[jdsmith]

When the new UPS is installed, the panels will be reconnected to the UPS, and the two breakers with undervoltage trip would remain as spares.

Steve

If you do end up going with UV trip breakers, you can get GE Spectra breakers with a field installable UV trip element that you can remove after the new UPS is installed.