The other day I was called out to examine an APC SMT1500C that had unexpectedly dropped power to a telephone and network rack. This particular UPS was only a little over a year old based on its serial number.
The red "!" lamp was illuminated and the display indicated the presence of an alarm code. I've forgotten the exact number given. I think it was 3.
Leaving it without power or battery connections overnight seems to have cleared the alarm code, at least temporarily. I'm still not convinced that it's working properly, as without a battery attached, the UPS repeatedly cycles its power supply. I have yet to see its batteries charge beyond the 97% mark.
I was quite surprised that there doesn't seem to be anything published regarding the nature of these alarm codes. Even if they can't be fixed by the end user, it would be nice to know what they mean. I downloaded the manual, searched the web and even wondered why the UPS's two line display might not go into more detail.
If the error was P.3 then it was possible a DC transformer imbalance. To correct removing the load and restarting the UPS should clear the issue.
The code has not so far reoccurred. However, I think the UPS is not working properly based on a few different things:
1. The cooling fan shuts off completely when the unit is running on AC power. I thought all the newer SMT series UPSes ran the fan at slow speed constantly.
2. If forced to run from battery, the fan starts but only runs slowly regardless of load. I tested it with a resistive load measuring to 60% of its capacity, and after a few minutes, the UPS started to smell like it was overheating.
3. In the event log, there have been two occurrences of "Charger Event 186".
The alarm code given by the UPS was b.04. The UPS serial number is 3S1752X04814.
The SMT fan will be off on initial start up, to limit initial current draw from the logic power supply. The fan will transition from off to low speed if the UPS goes on battery, internal temperature exceeds 55°C, load is over 75% in Green Mode or over 40% while AVR is active, or input is over 150Vac for the low voltage models. The fan should transition from low speed to high if the internal temp exceeds 60°C, or the load is over 75% on AVR or on Battery.
If you are using PowerChute to monitor the UPS, PCBE logs the UPS internal temperature and allows for cross checking whether the fan went to low / high speeds at the appropriate thresholds.
Charger events are usually set when the charger output voltage is either above or below thresholds - each charger event will be automatically cleared in 60 seconds and the charger will re-attempt operation.
I am surprised by the decision to change the Smart-UPS fan behavior back to the earlier method. Having the cooling fan running constantly at a slow speed definitely made a difference to the temperatures reported by the UPS's internal sensor.
I am still not confident this UPS is working properly. Three minutes into my load testing (60% of rated capacity, purely resistive), it began to smell as things inside the UPS were getting dangerously hot and the fan was still running at its low speed. I stopped the test before anything bad could happen. There is also the mystery of why it suddenly dropped the attached load.
The reported battery charge level dropped to about 65% during this time, and when I restored power to the UPS, it jumped almost instantly to 93% or so.
I will contact APC support and go through it with them as time permits. The UPS has not been monitored by any software.
Thank you Bill and Szabi for your assistance and information in troubleshooting this UPS. It is very much appreciated.
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