The Free On-line Aquaculture Dictionary |
Heating Systems |
System Type |
|
Immersion heaters |
Electrical immersion heaters (like the one in the
tank that probably heats your hot water at home) placed either directly
into the tank or part of the system are a good method for heating small
tanks and systems where either the water is static, or recirculated to a
high degree (which has the effect of keeping the heat in the system). Some
immersion heaters are available with their own thermostats, others require
a separate controller. When using immersion heaters it is advisable to
have three or four smaller units rather than one larger unit. This is
because if one of the elements fails there will only be a partial heat
loss, which will limit the stress on the fish. It is quite feasible to
link all the heaters to the same controller unit. Immersion heaters are most effective if they are
mounted horizontally in a tank rather than vertically. This gives a much
better distribution of heat through the water. If heating a large static
tank it is often advisable to have a small airstone or pump providing some
currents to assist in the heat distribution. In smaller thanks, the
currents caused by the hot water rising to the surface is often
sufficient. Immersion heaters can be difficult to control to an
exact temperature setpoint and frequently operate with a hysterises of 2-3oC.
This is because the electrical elements take time to heat up when turned
on and time to cool down when turned off. A programmable controller can be
used to give finer control, but the controller must first be “tuned”
to the ramp up and ramp down rates of the element. See controllers for
more detail |
Boilers |
Usually gas or oil fired, boilers use an ignited
fuel to heat an enclosed circuit of water. A heat exchanger is then used to transfer this heat to the farms
water supply. See diagram heatx.htm Boilers are commonly used where large amount of
heating are required. They are very simple systems, with mainly just the
burner part of the system requiring any special maintenance. Boilers, when
properly maintained are also very reliable. A boiler system is very cost
effective for a large flow system, when compared to immersion heaters and
are also easier to control
the temperature to a given temperature setpoint. |
Electrical |
Large electrical heating systems, which operate
either in line in a chamber (which makes them like immersion heaters) or
on an enclosed loop with a heat exchanger (like the boilers) are also
available. These systems are not usually economically viable compared to
boilers, except in some countries where electricity is very cheap. |