When utility power fails at a lift station, the wet well keeps filling whether or not the pumps can run, so a station that cannot pump on backup power will overflow. A standby power run strategy is the plan for riding through that outage: transfer to a generator, run what the generator can actually carry, and get back to normal when the utility returns. The catch is that a generator sized for the whole station is expensive, so most stations are built with a generator that can run only some of the pumps, which forces the control system to run fewer pumps and shed the rest. This guide explains the transfer sequence, why generator capacity limits pumping, and how a control system adapts pump control while on backup power.
Standby Power Run Strategy in one line: A standby power run strategy is the sequence and logic that lets a pump station keep pumping through a utility outage on a standby generator. When utility power fails, an automatic transfer switch disconnects the utility, starts the generator, and connects the station to it once it is up to voltage and frequency. Because the generator is often sized for less than the full station load, the strategy usually limits the station to running one pump at a time or sheds the lag pumps, then restores full operation and transfers back when utility power returns.
The heart of the strategy is the automatic transfer switch, which is the device that decides whether the station is fed from the utility or the generator and physically connects only one at a time. Under normal conditions it sits on the utility source. When it senses that the utility has failed or dropped out of tolerance, it starts a timer to confirm the outage is real rather than a momentary dip, then signals the generator to start. The generator cranks, comes up to speed, and stabilizes its voltage and frequency, and only when it is ready does the transfer switch connect the station load to it. This open transition, disconnecting from the dead utility before connecting to the generator, prevents ever bridging the two sources.
The delay before transferring is deliberate. A brief utility flicker does not justify starting a generator and interrupting the station, so the transfer switch waits out short dips and only commits to a transfer once the outage has persisted long enough to be genuine. Similarly, when utility power returns, the switch waits to confirm the utility is stable before transferring back, and it typically runs the generator unloaded for a cool-down period afterward rather than stopping it the instant the load is removed. These timers keep the generator from short-cycling on marginal power.
Throughout, the pumps must be handled carefully around the transfer itself. The moment of transfer is a brief power interruption, so pumps are usually stopped before the source changes and restarted afterward rather than being left running through the gap. A well-built sequence drops the pump calls as the utility fails, lets the transfer complete onto stable generator power, and only then begins calling pumps again under the backup-power rules, so no pump is asked to ride through the dead interval between sources.
A generator large enough to start and run every pump in a station at once is costly, and outages are infrequent, so stations are commonly fitted with a generator sized to carry only part of the full load. The determining factor is often the starting current of the pump motors, which is several times their running current, so a generator that could comfortably run two pumps steadily might not be able to start a second one while the first is already loaded. The result is a station that on utility power can run several pumps in parallel but on generator power can only support fewer.
This is why the classic backup rule is one pump at a time. During an outage the control system restricts the station to running a single pump, accepting a lower pumping rate in exchange for staying within the generator's capacity. As long as the reduced rate keeps up with the incoming flow over the course of the outage, the wet well is managed and the station rides through. Where a single pump is not enough, the strategy instead sheds the lag pumps, allowing the lead and perhaps one more to run while locking out the rest, so the running count is capped at whatever the generator can safely start and carry.
Load shedding can go further than just the pumps. Non-essential loads such as heaters, some lighting, or other equipment can be dropped during an outage to free up generator capacity for pumping, since keeping the wet well down is the priority and comfort loads are not. The strategy therefore has two levers: capping how many pumps run and shedding auxiliary loads, both aimed at fitting the essential pumping duty inside a generator that is deliberately smaller than the full utility-fed station.
For an unmanned station, the point of a cloud SCADA platform such as Merobix is that it knows the difference between normal and backup operation and changes how it runs the pumps accordingly. It watches the utility-power status, the transfer switch position, and the generator's running and ready signals, so it always knows which source is feeding the station and whether the generator is healthy. On that basis it switches the pump control mode: on utility power it runs the normal duty with all pumps available, and on generator power it enforces the backup rules, capping the running count to one pump or to whatever the generator supports and shedding the lag pumps and any non-essential loads.
The restart sequencing after a transfer is part of this adapted control. Rather than letting every pending pump call come back at once and overload the fresh generator, the logic brings pumps back one at a time with a stagger, so starting currents do not stack up. If the wet well has climbed during the transfer, the system prioritizes getting the lead pump running promptly to draw it back down, then holds off on any additional pump until the first is stable, all within the tighter capacity the generator allows. When utility power returns and the switch transfers back, the logic releases the restrictions and returns to normal multi-pump duty.
Because all of this runs at a site nobody is standing at, the monitoring side matters as much as the control side. The platform alarms on the utility outage itself, on the generator failing to start or failing to reach ready, and on the transfer not completing, because any of those means the station is now at risk of overflowing with no one there. It also trends fuel level, generator run hours, and how the wet well behaved during the outage, so operators can confirm the station rode through and can plan refueling and maintenance. Turning a power failure at a remote lift station into an immediate, understood alarm rather than a surprise overflow is the core reason the run strategy and the monitoring are designed together.
Standby generators are often sized for less than the full station load because a generator big enough to run every pump at once is expensive and outages are infrequent. The limiting factor is usually motor starting current, which is several times running current, so the generator may not be able to start a second pump while the first is already loaded. Restricting the station to one pump keeps it within the generator's capacity while still drawing the wet well down. If a single pump cannot keep up, the strategy sheds the lag pumps instead of running all of them.
An automatic transfer switch senses when utility power fails, waits briefly to confirm the outage is real, starts the standby generator, and connects the station to the generator once it is up to voltage and frequency. It connects only one source at a time, disconnecting the dead utility before connecting the generator so the two are never bridged. When utility power returns and stabilizes, it transfers the station back and runs the generator through a cool-down before stopping it.
The control system watches utility status, the transfer switch position, and the generator's running and ready signals, and switches into a backup mode when the station is on generator power. In that mode it caps the number of pumps that can run, typically to one, sheds the lag pumps and any non-essential loads, and restarts pumps one at a time with a stagger so starting currents do not overload the generator. When utility power returns it releases the restrictions and resumes normal multi-pump operation.
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