Power transfer detection

[Anonymous user]

I have a Smart-UPS 2200 RM with AP9619 card / Hardware Revision: A10.

AOS Version: v3.6.1, sumx Version: v3.5.8

There is an automatic transfer switch that switches to natuaral gas generator during the power outage event.

APC detecs the power loss as it takes a min or two for the generator to kick in, but when the utility power comes back APCs don't detect the interuption as the switch back to the utility power is instant. Is there an SNMP value I can monitor that would indicate the return of the utility power?

Thanks

[Terry_Kennedy_apc · Accepted solution]

When the transfer switch switches back to utility power, if the switch happens "cleanly" enough (which depends on the transfer switch and any synchronization the generator does), the UPS just sees it as continuous "utility" power, regardless of whether it comes from the actual utility or your generator. Since it doesn't see a change, it won't alert you or change its SNMP status. You probably received an "On battery power" notification when the power failed and a "No longer on battery power" when the generator started, but nothing after that, right?

If the transfer switch is an APC model, it will report the switchover (and back). If it is a non-APC model, then you'd need to check with its manufacturer to see if it supports that type of notification.

[Anonymous user]

Correct, I get "On Battery" alert and then a min later "No longer on Battery". No other alerts.

The transfer switch is ASCO, not an APC model. Even if ASCO supports the switch over notification I don't have any means to communicate with it and would require a communication module in the transfer switch to be installed.

I was hoping the switch over was not "clean" and APC could pick up the event, but it sounds like it can't.

Thanks for your help

[Terry_Kennedy_apc]

I assume this is a big (whole building or at least datacenter-size) transfer switch?

Depening on what you want to accomplish by detecting that the utility power came back on, you might be able to get that from the generator management interface.

There are also various other things you can do that are rather oddball solutions if you really need the alerts and can't get them any other way. Post back if you want to hear about them.

[Anonymous user]

Only datacenter is on the generator, which is probably to my advantage. I have several PDUs in the building that are not on the generator. I can set up SNMP monitoring of their network interfaces.

When building looses power i will get a "communication lost" alert and when it comes back i should get a "communication established" alert.
Not sure if you had something similar to suggest, but would like to hear what you had in mind.

[voidstar_apc]

Three possibilities:

- Terry is correct and the switch transfers cleanly.

- The waveform distorts, but not enough for the UPS to pick it up. You can try adjusting the UPS' sensitivity to high, however then the generator's AC may not be clean enough.

- The UPS does detect the transfer, but the loss of power is too brief to be recorded by the network management card. If you have a microlink UPS lying around, like an SMT or SMX model, try plugging it in and seeing if it detects the transfer.

Overall, I think it's more robust to monitor the transfer switch or utility power directly rather than looking at the output of the switch.

[wayne_i_apc]

Have you considered using the input contact feature of your AP9619 card? If you connect a set of contacts on an external relay to the proper AP9619 terminals, then wire the relay coil to operate from UTILITY power only (NOT generator or UPS power), the NMC can be configured to send messages on a change of state of the relay indicating both the loss and restoration of utility power.

I'm not sure if this solution is something that Terry would consider "oddball", but it would require some hardware skill to (safely) assemble this relay solution from the basic parts, but there may also be a commercially available relay package.

[Terry_Kennedy_apc]

It is kind of silly, but get an APC transfer switch and plug one source into the unprotected (before ATS) building power and the other source into the output of the UPS (this will likely need an adapter cable from 5-15P to L5-20R). Don't plug anything into the outlets on the transfer switch. Set the APC transfer switch to prefer the unprotected building power. Connect the network cable from the APC transfer switch to equipment which is also protected by a (possibly different) UPS, so that when it tries to send email / SNMP / whatever alerts, it succeeds.

When the utility power fails, the APC transfer switch will still be receiving power from the UPS it is plugged into. It will report a transition from source A to source B, via email / SNMP / whatever you configure. When the utility power comes back, the APC transfer switch will select that again (and send notifications) since you configured it to prefer that source.

Plugging one source of the APC transfer switch into the UPS is important, as otherwise it will lose power because your generator takes time to start after the utility power drops. While the management card in the APC transfer switch is booting, it can't send notifications. Having one of its sources plugged into the UPS guarantees that it will always have power and be able to report what is happening with the utility power.

As I said, kind of silly, but it does let you accomplish the monitoring you requested without getting involved in the building ATS / generator /etc. issues.