We've spent recent months hammering away at power issues and reviewing records of failed UPSs, protectors, fuses and gear from customer sites. There's a misconception that moving key applications to the cloud negates the need to maintain infrastructure and improve the functions that keep availability high.
Dual Conversion UPS
It’s an old adage that, "You get what you pay for," but when it comes to a UPS, add "maybe." Just because a UPS has dual conversion doesn't mean it will survive a series of hits or blown transformers. But the idea is, better to have a dead UPS than dead network and other gear attached to the UPS; dual-conversion UPS protects that gear from the effects of power hits.
Last year a stainless steel cover over a power receptacle was literally blown away by a power disturbance on one of our sites. The connected UPS didn't survive. The breaker on the sub-panel tripped and all the gear connected to each rack mounted Transient Voltage Surge Suppression (TVSS) power distribution unit (PDU) remained unharmed. The rack-mounted TVSS connects to the UPS. We often have more than one UPS in a rack and each PDU is dedicated for a specified load. The UPS then connects to a power receptacle.
After examining service records, we noted the frequency of battery and UPS failures and then some unexplained equipment failures. Earlier this year, we deployed ONEAC power conditioners to multiple sites of this customer's network.
Let-Through Voltage
The amount of let-through voltage that a UPS or TVSS device allows is sometimes stated by manufacturers as low or lowest let-through voltage and that may not be accurate. What may not be stated in gear specifications is the clamping time or how quickly it responds to transients and spikes and at what voltages.
We used ONEAC wall mounted power conditioners and as a word of caution, never place power conditioners on the floor because of water, spillage or cleaning staff. Then, because these particular units are wall mounted, remember to have a fire rated substrate to mount the gear. The UPSs now connect to the power conditioner. This proved to work well as the sites survived the recent "Derecho" storm system that plagued our area a few weeks ago.
But it still doesn't resolve all power issues. Batteries still fail and flywheels and backup generators aren't an affordable option for many.
Another concern is that staff and vendors don't load-mange the UPS and instead see empty receptacles on the UPS as an invitation to plug in more gear. The UPS must be adequately sized and managed, otherwise you can expect failed units and downtime.
In this customer example: The receptacle is dedicated 30Amp circuit/breaker that feeds two duplex receptacles. The power conditioner output load is rated at 12 Amps and connects to one receptacle. There are three 120 VAC UPS units rated for 700 watts each that connect to the power conditioner. There are three PDUs and each is rated at 15 Amps but only carrying a load of 175 watts of 120 VAC gear. The power conditioner is using about 50 watts and is operating around 93% efficiency or power factor (PF).
Because the power conditioner has a high PF of 93%, less heat is in the closet, and the same is true of the ADTRAN gear that operates in the rack. We measured the total load on the power conditioner and it is 5.17-5.25 Amps depending upon traffic/usage.
The UPS's PF is only 80%, so most of the heat generated in the closet is from the UPSs and they provide under an hour of battery backup. With the power conditioner, the customer can expect a few more years of life before upgrading them to units with better efficiency (higher power factor) that produce less heat and cost slightly less to operate.
Power conditioners are expensive but they will add life to your gear, and availability may increase a notch. Cycling the batteries and replacing them proactively is better than waiting for failure. When you have the history of the UPSs and how long the batteries last, then shave a few months off of whatever their average life is and plan on replacing them at that interval. Proactive is always cheaper than reactive and the larger battery configurations are no exception.
