AC Versus DC Powered Battery Back-Up Systems
A DC based back system typically consists of a DC pump, a 12 volt serious cycle battery (2 batteries when a 24 volt system), and a charger. Most DC pumps used with regard to a back-up system were initially designed to be bilge pumps for boats and tend to be not heavy duty, however, many work well. A characteristic of some sort of DC system versus a great AC system is that the rate that it discharges is related to the degree that the battery power source is charged. A completely charged 12 volt battery perseverence the DC pump to help its maximum capability. As the charge of the power is consumed, the pumping rate with the DC pump diminishes. For example, a given pump will discharge at the rate of 30 gallons for each minute with a fully billed battery, but may only end up pumping at 15 gallons per minute when half of the charge holds left with the battery. At the end when the battery is about to become depleted, the pump may be discharging at less than five gallons for each minute. DC systems efficiently consume DC current that will run continuously for a long time (up to 10 hours continuously and intermittently for many days).
An AC based back-up system typically is made of an AC heavy job pump, a 12 volt deep cycle battery (or two batteries when a 24 volt system), and an inverter which includes a battery charger). An inverter converts the DC power with the battery to its AC counterpart. Unlike a DC pump, an AC pump will run close to its maximum potential capability until the battery charge is broken down. For example, if the AC pump can pump at a rate of 50 gallons per minute, it will continue at close to this rate (with minimal loss over time) until the power supply source is depleted. One must always select an AC send with efficient amperage rating (3-7 amp hours), otherwise the system will not run long enough before the battery source is depleted along with the system shuts down. An efficient AC pump can discharge even though the best DC system because it is discharging at a better rate than most DC systems though it shuts down faster compared to a good DC pump system. The key advantage of choosing an AC system is it's easier to match it up with its primary pump counterpart. Since the AC system requires a great inverter, it is typically more costly than DC systems which do not require an expensive inverter due to the operation.
The best way to compare different available solutions is to compare the total amount of gallons discharged using a given battery (beginning with a fully charged battery recommended by way of the manufacturer) and that the data, ideally determined by an unbiased testing agency, represents the time and performance until the system shuts down). The values will need to have been generated at an 8-10 ft. head. The head is the distance that the pump discharges vertically (in a basement, it is typically 8-10 ft).
Typically, A DC system will discharge at a rate less than the prime pump can discharge. Whether this is certainly good enough is something that the homeowner and/or contractor must produce a judgment call on. An AC system can be matched more effectively on the performance of the primary pump. The best scenario is that the homeowner has determined how effectively his primary pump has performed within a major storm and matches that performance to be able of the back-up system, whether it be an AC or a DC system.
REFERENCE:
http://www.articleways.com/Art/69805/7/Spending-A-Great-Time-With-Your-Dad-on-Valentine-s-Day.html
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