Written By David Terceria, BFAS
I would like to introduce you to a product that has been saving
me many sleepless nights. As many of you know, I am responsible for the well
being of the aquarium livestock at a local pet store. Currently, I am maintaining
48 display tanks, 24 quarantine tanks, and 16 hospital tanks. Amongst other
responsibilities, it requires the need to be on call in the event that power
outages threaten to shut down the entire life support system of the aquariums.
In the past, the routine for such a power outage involved the setup of small
battery powered air pumps (each using 2 D size batteries) shared between the
many aquariums. Although this method was effective, setup was quite time-consuming,
and on several occasions the power would be restored just as the last pump
was being installed. Partly to improve the well-being of the fish and mostly
for my own sanity, a new back up system was installed. This back up power
system would be a welcome addition to any fish room.
Under normal conditions in the fish room, the quarantine and hospital tanks
are filtered by air driven box filters and the display tanks are divided between
five separate central filtration systems. A linear piston pump supplies the
air for the hospital and quarantine tanks with a blower as a backup. The linear
piston pump is the main air supply because of its quiet operation, and the
blower was used as backup because it was less expensive. Ideally, a pressure
switch should be installed to turn on the blower if the piston pump should
fail, but for now I can manually switch between the two. For battery backup
I installed the Tripp Lite APS 512 automatic power system. I am sure that
there are other power converters on the market, but I will discuss this one.
I have personal experience using the Tripp Lite APS 512 and am very pleased
with its performance.
The APS 512 is a 400 watt inverter that incorporates a three stage battery
charging system (Bulk, absorption and float) that will charge and maintain
either wet or gel batteries. You have the option of connecting a single 12
volt battery, multiple 12 volt batteries, or multiple 6 volt batteries depending
on your power requirements. The air pump will operate on 120 volts until the
power supply is interrupted, at which time it will automatically switch to
the DC converter. For the hospital tanks, this addition of the APS was all
that was needed to maintain the existing filtration during power outages.
For the display tanks that ran on central filtration, a PVC airline was installed
above each system with an air valve for each tank. Airline hose was cut to
reach each tank and air stones were attached. Box filters are currently stored
in the sumps of each display unit. In the event of a power outage for more
than a few hours, the box filters replace the air stones and offer biological
filtration in the display tanks.
To choose the right size inverter and batteries to match your particular system
you must first determine your total wattage required. You may want to sustain
only minimal life-support systems to keep the cost lower by using a lower
wattage rated inverter with fewer batteries, but I suggest allowing for one
small low wattage lamp in the fish room so you can monitor the operation of
the equipment at night. The wattage rating is usually stated in the equipment
manual or on the equipment nameplates. If your equipment is rated in amperes,
convert to watts by multiplying the ampere rating by your nominal AC (120V).
This is the formula that I used but it is only correct for incandescent lighting
and electric heaters, and should not be used for motors. If your power load
includes inductance magnetic devices like lamp ballasts, solenoids, motor
windings, transformers, etc. the formula that you should use for a single
phase load is:
volts
X amps X power factor = watts
Often the actual watts used are significantly less than what would be calculated
by simply multiplying voltage X amps. This is especially true when you are
using linear air compressors or magnetic drive pumps. You can determine the
wattage consumption of a motor by testing it using a watt meter. Once you
have determined the total wattage required you must select an inverter that
meets or exceeds this demand. The Tripp Lite 400 watt inverter retails in
the U.S. for approximately $400, the 800 watt inverter retails for approximately
$100 extra.
For optimal performance and longer life, select deep cycle batteries instead
of normal car batteries because they are designed to withstand continuous
discharge and charging situations. When using wet cell batteries, it is important
to consider the location where they are to be kept. It must be a well ventilated
area or explosive hydrogen gas can accumulate. In situations where this is
not possible, gel cell batteries should be used because of their sealed construction.
You should use the shortest and heaviest gauge battery cabling to limit DC
voltage drop and allow for maximum transfer of current. I suggest using no.
4 cabling for lengths up to 10 feet and no. 2 cabling for lengths up to 16
feet.
To select the battery amp hour capacity (i.e. the time it takes a battery
to discharge with X amps been drawn.) that will be required, divide the total
wattage required by 12 to determine the DC amperes. Multiplying the DC amperes
required by the number of hours between battery charging (how long the power
can be out before you start to panic) to determine battery amp hour rough
estimate. Battery amp hour ratings are usually given for a 20 hour discharge
rate. Actual amp hour capacity is less when discharged at a faster rate. To
compensate for this discrepancy, multiply the battery amp hour rough estimate
by 1.2 to determine the optimal battery amp hour size.
IE. Total watts = DC amperes
12
(DC amperes) X (# hours acceptable power outage) = battery amp hour estimate
(Battery amp hour estimate)X (1.2) = optimal battery amp hour rating
Multiple 12 volt batteries can be connected in parallel to achieve higher
amp hour ratings. I used four high-performance deep cycle batteries designed
for inverter use in my system which gives me approximately seven hours of
power before recharging.
Within a week of installing this new system, we were hit by a major hurricane
that knocked the power out at the store for three days. Although I only had
enough battery power to last seven hours I was able to charge the batteries
during the day by electric generator and to return home at night for some
well-deserved sleep. Whilst the Tripp Lite APS 512 was not inexpensive, I
found the cost was well justified.