What Causes Fish Tank Heaters To Fail?

As the bimetallic strip bends toward and away from contact, an electric arc is created that eventually will pit and corrode the points. To prevent this, a condenser should be attached across the circuit, above the thermostat. Should the condenser short out, the current would bypass the thermostat, which would then not be operating. The heater, with no control on it, would continue to heat.

Better thermostats today have a fuse in series with the condenser. Should the condenser short out, the fuse will blow. The thermostat and heater, however, continue to function without the condenser and fuse assembly until they can be replaced.

Another cause of trouble is water in the thermostat tube. In this situation the heater continues to function but without any shut off control.
Occasionally, although not frequently, the silver points that are used today melt and fuse together. This prevents normal opening of the thermostat and is usually a possibility when the power source is direct current (D.C.). Cleaning the contact points occasionally with very fine sand paper will help correct this trouble.

The most common causes of heaters failing to heat is usually current failure, or improper contacts in the wall plugs. Occasionally the thermostat plug becomes disconnected without anyone realizing it. All that is necessary to restore its function, of course, is to plug it back in.Even more infrequent is a burned out heating oil, or a broken connection within the circuit itself.

Heaters fail to heat only a fraction of the number of times they overheat. It is hoped that the number of times the latter occurs will be lessened considerably by the use of proper fuses.

A magnetic snap action thermostat is a thermostat that operates on the same principle as the ordinary thermostat, but with the following addition. There is a small magnet at the end of the bimetal strip and a corresponding plate on the mounting. As the bending bimetal strip comes close, the magnetic attraction asserts itself, closing the contacts sharply with a snap—hence the name. This rapid closing eliminates the problem of the arc and the necessity for the installation of a radio condenser.

A Guide To Aquarium Hood, Heater, and Pilot Lights

A reflector is usually only 3-1 or 4 inches wide and covers only the front few inches of the aquarium. A hood covers the entire tank. Usually, although not always, the sockets in a hood is set in the center.

The hood, which requires more material and labor to make, is more expensive. It offers the advantage of protecting the tank from dirt and dust and preventing excessive evaporation.

A glass cover and a strip reflector are sufficient for covering and lighting your aquarium.

Commercial full hood is constructed of a light-weight unbreakable plastic. The front piece is hinged so that you can easily feed your fish.

A fish is physiologically suited to living within a certain temperature range. By exercising proper care one can safely bring it to the limit of that range—a limit which varies somewhat with individuals and their condition, as well as with species.

An electrically operated heater equipped with a suitable thermostatic control is the most inexpensive and trouble-free method.

A control unit employing a bimetallic strip which automatically responds to temperature changes and turns the heater on and off.

A pilot light is a small light which is hooked into the heater to indicate whether the current is on or off. It remains lighted as long as current is flowing through the heater. The pilot light may be installed inside the tube which holds a combination heater and thermostat; it may be in a separate tube with either the heater or the thermostat; or it may be the plug-in type that fits.

You should make it a habit to check all thermostats regular highly. If, in checking, you find that the tank temperature is higher than the thermostat setting and that nevertheless the pilot is still on, you have a strong indication that the thermostat has failed to shut off. It is entirely possible for the tank temperature to be higher than the thermostat striking the tank. However, when such external factors are causing the temperature rise, the thermostat connection should be open and the pilot light off.

It is also a sign of trouble when the temperature is lower than normal and the pilot light fails to indicate heating. This condition should be checked and corrected. Cheap heater-thermostat combinations can chill or cook your fishes.

Aquarium Heaters for your Tropical Fish Tank

Heaters are no more expensive than any other small electrical appliance. Remember, heaters are using up electricity only when they are heating. Thermostats do not use up any current; they only conduct it or cut it off.

The warmer you keep your tanks in relation to the room temperature; the more electricity will be required. If you are concerned about the cost of electricity, keep your tanks in the warmest part of the warmest room - but not near a radiator - and maintain your tanks at the lowest safe temperature of 72° to 73° F.

Incidentally, it costs no more to operate a large heater when a small heater in the same size tank. The larger heater will simply heat up that much faster and shut off that much sooner. Many people are under the misconception that a heater gives off only the temperature at which the thermostat is set while heating. This is not so. A heater, once it starts heating, gets as hot as the resistance wire will allow, and stays at that high temperature until the thermostat shuts it off. Then it loses all its heat to the water. A heater does not feel hot to the touch while it is heating, because it is rapidly exchanging its heat with the water. The same heater in air becomes too hot to touch within seconds.

A test light can be wired to a heater, provided you know how to make the hook-up. If the test light goes on when the thermostat and heater are plugged in, turn the temperature control down until the light just flickers off. If the light fails to go on, turn the temperature control higher. The point at which the light flickers on or off is where thermostat is set for room temperature. A thermometer in the room will tell you what the room temperature is. From there it is a simple matter to turn the thermostat up or down.

If the light goes on and fails to shut off when the thermostat contact is broken, it is usually evidence of the failure of a condenser, which should be removed. The heater should then function normally. A new condenser should be put on as soon as possible, rather than operating without it. The absence of a condenser puts a strain on the contact points.

If the test light fails to go on, check the male plug and the contact points first; then look for a break in the element, or a black spot, which indicates a burned area.

Occasionally the points become so coated with carbon that they fail to make proper contact, or constant arcing may build up a high spot, preventing the contact from breaking properly. Fine sandpaper used carefully will remove those spots and return the unit to proper operating.

How Does an Aquarium Thermostat Operate?

Aquarium thermostats all utilize the same principle with variations only in quality, construction and design. The basic principle behind a thermostat is that metal, when heated, expands; and that different metals expand at different rates. Two flat strips of different metals are bonded together. When heated, the metals’ unequal coefficients of expansion result in a bending of the strip. One end of this bimetallic strip is fastened rigidly in place and one end of the circuit is fastened to it. The other end is free and rests against a screw in a metal plate to which the other end of the circuit is attached.

As the bimetallic strip warms up, it curls away from the screw against which it is resting, thus breaking the contact and the circuit: With the circuit broken, the heater stops heating. As the water surrounding the tube cools, the drop in temperature is transmitted to the bimetallic strip, which - being cooled - straightens out again and re-establishes contact and turns on the heater.

The screw against which the lower end of the thermostat rests is threaded and may be turned to increase or decrease the distance between the points of contact. This varies the extent to which the metal must bend in order to make or break the contact. The metal always expands and contracts the same distance at given temperatures. Once the proper spacing has been reached for the desired temperature setting, it is only necessary to leave the screw setting alone.

The closer the contact points, the more heat is required before the circuit opens. The farther apart, the colder it must get before the contacts come together. In order to raise the aquarium temperature the adjustment screw is turned so as to bring the points closer together, and to lower the temperature, the points should be separated.

All adjustments should be made gradually and checked frequently with a thermometer to avoid sudden extreme changes of temperature. Usually a quarter turn is sufficient to raise the temperature 3° to 5°.

Some of the more elaborate thermostats have adjustment knobs projecting above the top. They are connected Icy means of threads or movable plates to the contact points. However, the principle remains the same: varying the distance between the contact points determines the temperature at which the circuit will open and close.

Some aquarium thermostats are sensitive to as little as 1 1°. However, such extreme sensitivity is not necessary; usually + 3° is adequate for aquarium use. Some cheap thermostats are even less sensitive and less satisfactory.

Most thermostats arc made to operate at an adjustment between 60° and 110°. Should you try to set the thermostat temperature lower than 60′, the adjusting screw would be at too great a distance from the bimetallic strip, and contact could not be established. Conversely, should you attempt to set the thermostat for more than 110° the screw would be pressed so tightly against the thermostat that the strip could not curl far enough away ever to break contact and stop the flow of electricity.