Out of warranty AP7752 fluttering between power sources. Help!

[Anonymous user]

This unit is about 2.5 years old since installation, about four years old by MFR date.  When it's plugged into two power sources, it flutters between the two (click-click-click-click) and has even popped a circuit breaker due to this.  I replaced it with our spare, but as a several-hundred $$ unit, I'd like to know if it can be repaired before we go out and buy a new one.

Can anyone help?

Dave R.

[BillP]

The original firmware did not support out of phase switching and we don't really suggest using these with a generator. It is likely that source A and B are out of phase and could've potentially damaged the unit.

Even if the other ones are still in operation, it is worthwhile to see what revs they are at to prevent future problems. It is also feasible they could be damaged if exposed to out of phase switching or a generator and it won't be identified until too late.

Tripping upstream breakers is usually an indication of welded relays due to out of phase sources and a hardware issue. Can you verify the firmware version numbers on this one for now and your others? What about access to the event log?

AP7750 is an older generation product (replaced by AP7750A now) that also does not support out of phase switching. AP7752 and the other models listed in the following link can at least be upgraded -> INFORMATION BULLETIN - Upgrading Rack ATS Firmware (AP77XX) - potential to permanently damage ATS du...

[Anonymous user]

Thank you.  I'll test this either today or tomorrow on this unit.

Where this was in production, the 'A' side was Gen/Flywheel UPS, and the street-side is not backed up in any way.  Two others in the same Data center configured the same, along with another 13 AP7750's (Installed in 2010) in the same building connected the same way are running fine.

We do monthy Generator tests (JACHO requirement), so the street sides are dropped monthly for all these units.

Dave R

[BillP]

I am just realizing you referenced "on-net" so I take that to mean on the network?

Not sure if you need set up instructions but they are here (this is an NMC1 device and if you have its serial cable, its a RJ-12 to DB9, part # 940-0144 - if none of the other methods are an option anyway)->http://www.apc.com/support/index?page=content&country=US〈=en&id=FA156064

I also don't think we've ever tested this with a Flywheel UPS..

Anyway, the log might report something obvious too - i.e. power supply fault.

[Anonymous user]

This unit is about 2.5 years old since installation, about four years old by MFR date.  When it's plugged into two power sources, it flutters between the two (click-click-click-click) and has even popped a circuit breaker due to this.  I replaced it with our spare, but as a several-hundred $$ unit, I'd like to know if it can be repaired before we go out and buy a new one.

Can anyone help?

Dave R.

[BillP · Accepted solution]

Hi Dave,

First thing I'd do is log into it if you can and tell us what firmware is on it.

The event log in the device and just the current status in the interface may be very helpful in assisting with identifying the problem. The unit could've been damaged due to older firmware and being installed in a location with out of phase sources or a simple setting change based on the recommendations here (Common Rack Automatic Transfer Switch Scenarios and Questions | FAQs | Schneider Electric US) may help after we verify other bits of information I asked above.

Also, what are the input sources for A and B you're using currently (utility power, generator, UPS, etc)? Where was this installed previously and what were the input sources at that time?