How Pump Sentry Works

Pump Sentry interfaces between pumps and the AC electrical supply. When electricity is available. Pump Sentry charges a battery and monitors the power line to detect a power outage. At the instant that power failure occurs, Pump Sentry draws energy stored in this battery and converts it to AC power. This AC power is automatically channeled to the pumps to maintain their operation in the absence if electricity.

When AC utility power is restored, the Pump Sentry reinstates AC utility power as prime energy source to operate the pumps. Simultaneously and automatically Pump Sentry commences the recharging of the battery, to return it to full capacity in preparation for the next power failure.

A deep cycle marine battery with 180 minutes reserve capacity will maintain the operation of a 1/3 Hp. column sump pump continuously for four to six hours. If more time is desired a larger battery or multiple batteries can be used. The operating time is directly proportional to the battery reserve capacity.


how it works

How to Calculate Operating Time During Power Outage

Operating time will depend on the following:

a) The size of the battery bank i.e. its total Ampere-Hour (A-hr) capacity.
Ampere-Hour capacity is calculated by adding the A-hr ratings of all the batteries in the battery bank where the batteries are connected in parallel.
(For Parallel Connection See Fig. #2)

b) The current draw for the pump in Amps (C).
This can be read off the nameplate on the sump pump

c) The average operating duty cycle of the system
The duty cycle of a system is the ratio of its "on" time to its "on" time plus "off" time e.g. if a pump will work for 10 seconds and is then off for two minutes (120 seconds) its duty cycle is calculated as follows:

Duty cycle = 10/(10+120) = 0.077

Once (a) (b) and (c) are known the operating time of a pump sentry in hours can be calculated by the formula:

T= A - hr/(C x 10 x D)

e.g. for a system with 1 battery rated 90 A-hr.
1) 1 battery rated 90 A-hr., A-hr = 1 x 90
2) A sump pump that draws 9 Amps, C=9
3) Duty cycle which operates 10 seconds "on" followed by 3 minutes (180 seconds) "off", D = 10/(10 +180) = 0.053

T (Hours) = (1 x 90)/(9 x 10 x 0.053) = 19

In 10 seconds the average 1/3 hp. sump pump will evacuate approximately 10 gallons of water.