ECO/ESS Mode Exposed
In the UPS industry, many high tech companies are engineering based while others are less technical and marketing based. This paper discusses a marketing feature that does not turn out to be sound from an engineering view but it sure sounds good initially.
In the UPS industry marketing driven companies do not lead the marketplace in efficiency or technology. To sound as if they do, new concepts are offered under names such as ECO or ESS Mode. ECO/ESS systems power the mission critical load on commercial power and switch to battery powered inverter or double conversion mode when the power fluctuates. This allows claims up to 99% efficiency; however the UPS is essentially also off in this mode. The major benefits presented by a quality UPS are power quality and power continuity. ECO/ESS mode eliminates power quality as a feature and may or may not always provide power continuity. The proof is in these manufacturers own documentation. Buried in the back of one such unit’s operation manual, it states “When the UPS is operated in ESS mode, commercial AC power is supplied directly to the critical load…” Further it confirms, “the UPS actively monitors the critical bus for power disturbances.” “If …. disturbances are detected, the system transfers to battery mode for minor disturbances and then to double conversion mode for more severe disturbances.” After the load has been supplied bad power (spikes, sags, noise, fast interruptions , the UPS will switch to battery and only possibly to full double conversion mode!!! This is similar to closing the barn door after the horses have run away. With the UPS's monitoring and reaction time a fluctuation or outage will be passed through to the load as the real UPS components are brought online! At least they’re somewhat honest on that part. However, that honesty turns to deception when one learns that while the UPS is operating on its static bypass circuit (passing commercial power to the load) the unit display indicates it is operating on line. The manufacturer has redefined what they and the industry have always properly called on line. This particular manufacturer highlights their unit as being 99% efficient. They just happen to forget to tell you that as far as the load is concerned the unit is also off. It’s easy to be 99% efficient when doing nothing.
One can also imagine what the battery life will be when the UPS goes to battery for any variance seen in commercial power. Perhaps this is why ESS units only have a 1 year parts and 90 day labor warranty. For years the industry has strived to provide 1 to 2% or better quality power to critical loads while utility fluctuates as much as -30% to +10%. The ECO/ESS concept reverses that to allow disturbances, fluctuations and surges through to the load. The true efficiency of that 99% ECO/ESS UPS is the same old 94% or less. Nothing changed except the marketing concept. The job of a quality UPS is to provide clean power all the time and less than 1% of the time it provides battery supported power. Units with ECO and ESS mode do not do this. Do not purchase a unit based on claimed efficiency only to later realize it needs to run in non-efficient mode to protect your load. As engineers and technical people we should not permit a marketing concept to replace sound engineering.