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Basic Operation on How a Water Heater Works

By Donald Kerr
Basic Operation on How a Water Heater Works

A description of the basic elements of a Hot Water Heater and an explanation of how different heaters work.

A: Pressure Relief valve. Safety device to prevent the tank from exploding should the pressure exceed limits. Note that in the diagram for the gas version, the pressure release pipe appears to be on top of the thermostat unit, this is not the case in real life, but the release pipe comes down close to the floor and the thermostat control is located clear of this pipe.
B: Hot water out.
C: Electric heating elements. Each may have its own thermostat, or could be both controlled by a single thermostat.

D: Cold water in & shut off valve.
E: Drain Tap.
F: Exhaust vent for combustion flumes, piped to the outside.
G: Thermostat control / shut off & pilot light control.
H: Gas Burner.

Water heaters come in a variety of sizes including 40 gallons, 60 gallons or more. Insulation surrounds the inner tank to help reduce heat loss.

Sacrificial Anode

Another note that is not shown in the diagrams, there is what is sometimes refered to as a sacrificial anode, this is a metal rod that extends into the water tank which is usually made of magnesium or aluminum this helps prevent corrosion of the tank itself. A process called Electrolysis eats away the anode (that is why it is called the sacrificial) instead of the steel of the tank. Once the anode is gone , corrosion of the tank will begin. The anode is usually screwed into the water tank from the top and can be replaced.

A Couple of Good Routine Self Maintenance That You Can Perform.

1. About every six months, open the drain and let about 5 gallons of water drain or until clear, this will prevent an accumulation of sentiment in the tank.

2. About once every year, test the pressure relief valve (A in diagrams) by opening the valve manually (put something under the pipe to collect the water or at least keep your feet away from it as this water is HOT, if it doesn't open then shut off the water to the heater and open a hot water tap in the house to release pressure, drain the tank and replace the pressure release valve. This valve is for your own protection, in the case of extreme over pressure, this valve is to automatically release critical pressure preventing the tank from exploding.

Gas Hot Water Heaters

For Gas hot water heaters, the unit heating system, consists of a gas burner that sits under the inner tank, combustion flumes are exhausted up thru a pipe that goes up thru the center of the inner tank and connects to another pipe at the top of the tank to carry the deadly flumes to the outside. On the outside of the hot water tank is a thermostat control / gas shut-off control / pilot light control. The gas control unit are usually made so that it will shut off the gas if it detects that the pilot light did not light. How does it know? By having a temperature sensing probe mounted in the path of the pilot light flame, if the pilot light temperature probe does not detect heat, gas will be cut off.

The Pilot Light

To light the pilot light, there will be a pilot light position or button that you will have to hold or push in and hold . light the the pilot and wait for up to one minute for the pilot light temperature probe to heat up, then release the control or button. S hould this heat sensor fail, your hot water will not work until this probe is replaced.

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