Heating, Cooling and HVAC

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Components of the Gas Hot Water Heater
The standard “tank type” water heater is found in most homes and with just a little maintenance, provides years of trouble free operation. Unlike tankless water heaters which have no storage stank, the tank type water heater heats cold water and stores the hot water until it is needed. This tutorial will give you a clear understanding of the components which make up the tank type gas water heater.
The gas water heater works by a law of physics called convection which loosely paraphrased, states that heat rises. Now please don’t run off just because I said “physics”. Heat rising and convection is a simple rule that you live with everyday and a hot water tank is no exception. Cold water is supplied to the tank and injected at the bottom of the tank through a dip tube. The denser cold water stays there and is heated by the gas burner. As the water heats up, it naturally rises (physics again…) and is drawn off by the hot water discharge pipe. You’ll notice in the diagram above that the hot water pipe is much shorter than the cold water pipe. This ensures that only the hottest water is being used from the tank. The hot water heater has simple parts and some safety features.

Let’s see the details of each major component of the hot water tank.

WATER SUPPLY & DISCHARGE:-
Cold Water Supply
Cold water is provided to the tank by a cold water supply line and controlled by a shutoff valve. It is important to know where the water supply shut off valve is located so maintenance can be performed on the tank.

Hot Water Discharge
This is the business end of the hot water heater and the hot water line is what supplies all your sinks, tubs, showers and appliance needing hot water.

TANK CONSTRUCTION:-

Construction of the Hot Water Tank
The tank jacket itself is made of steel and encloses a pressure tested water storage tank. Between the storage tank and the tank jacket is insulation to reduce heat loss of the heated water. It is a good idea to supplement the insulation by adding a fiberglass insulation tank jacket to the outside of the hot water heater. These are inexpensive and easy to install.
Inside the tank you will see a dip tube. The dip tube is where the cold water supply enters the tank to be heated by the gas burner. Since cold air and cold water is denser than hot air or hot water, the cold water sets at the bottom of the tank until it is warmed by the burner and heated enough to rise (through convection) to the top of the tank where the hot water hangs out. See, more physics…

In glass-lined tanks there will also be a metal rod in the tank, usually magnesium or aluminum) called a sacrificial anode. The anode rod is bolted and fastened to the top of the tank and extends deep into the tank. It’s purpose is to draw corrosion to itself instead of the metal tank. Some models do not have a separate anode but combine the function of the anode with the hot outlet. Plastic lines tanks do not have an anode.

GAS BURNER CONTROL AND BURNER ASSEMBY:-
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Gas Burner Control Module
The natural gas or propane is supplied by a pipe having its own gas shutoff valve. Just like you need to know where the water supply shutoff valve is located, you need to know where the gas line shutoff is located too. The gas line fees into a gas burner control module that serves as a kind of thermostat for the water heater. It also controls the ignition of the pilot light.
From the control module we now proceed to the gas burner assembly. This includes the pilot light and gas burner itself. The pilot light and burner adjustment are key to proper and energy efficient operation of the water heater. The gas flame should about 1/2 inch in height and should have blue tips.

EXHAUST FLUE:-

Gas Combustion Exhaust Flue
The exhaust flue serves two purposes. It exhausts combustion gasses from the burner and it serves as a type of heat exchanger helping to heat the water in the storage tank. The flue must be properly exhausted to the outside and there are specific code requirements for the type of flue construction and acceptable details.

PRESSURE RELIF VALVE:-

Temperature and Pressure Relief Valve
A safety feature of the hot water heater includes the pressure relief valve and discharge pipe. It operates like the radiator cap on your car. The purpose of this valve is to relieve excessive temperature or pressure build up inside the tank if it approaches the limits of the tank’s safe design range. This valve is located on top of the tank and often is threaded directly into the tank top itself. To test the valve lift up on the handle slightly and hot water should discharge out of the overflow pipe.

DRAIN VALVE:-

Tank Drain Valve
The hot water tank can build up sediments in the bottom of the tank if left unmaintained and by draining the tank using the tank drain valve these sediments cannot build up. And if you don’t have sedimentation then that helps to prolong the life of your tank and improve your water quality.

Prepare the tank for flushing by performing the following steps:

*Turn off power to an electric water heater. Do this by turning off the circuit breaker or fuse powering the heater.

*Turn gas pilot control valve to “pilot” setting.

*Shut off water supply to water heater.

*Open nearest hot water faucet.

*Attach hose to drain valve.

FOLLOW THESE STEPS TO FLUSH THE WATER TANK:-

CAUTION: When flushing your water heater there is danger of being scalded. Be careful and keep children and pets away during the procedure.

Water heater manufacturers recommend flushing sediment from your storage type water heater periodically. How often your model needs to be flushed depends upon the quality of the water in your area. Areas with high mineral content will have to flush more often.

What is sediment, and why is it a problem? The sediment is sand or other grit from a well, or any other material that has gotten into the municipal water mains. Sediment can also come into your home after the water company flushes out their lines.

Over time, your heater can accumulate this sediment consisting of sand, gravel, grit, and various mineral deposits. This buildup can reduce the amount your water heater holds, create a variety of interesting noises, and reduce the efficiency of your unit. The buildup of sediment at the bottom can harden and sometimes clog the drain valve.

Cleaning this sediment from out of your water heater is not particularly difficult, here is how to do it.

If your water heater is gas, set the gas valve to “Pilot” to prevent the burners from coming on while you are flushing it. If your heater is electric be sure to turn off the circuit breakers. With an electric water heater, if the water level drops below the heating elements and the thermostat turns the elements on, the heating elements will probably burn out quite rapidly.

Connect a garden hose to the drain valve at the bottom of the tank. Make sure the outlet of the hose is in a safe area away from pets and children. It can be very hot and can scald quickly

Close the shut off valve on the cold inlet to the water heater.

Carefully open the temperature/pressure relief valve at the top of the tank by lifting the lever. Leave the valve open.

Open the drain valve at the bottom of the heater allowing the water to flow out through the garden hose. If the sediment is clogging the drain valve then try closing the temperature/pressure relief valve and turn the cold inlet valve back on to “power flush” the sediment out.

In some cases the sediment hardens into large chunks that can block the drain valve. If so, then wait until everything cools down, remove the garden hose from the drain valve, remove the valve if necessary, and use a long screw driver to break up the clog. This is a very messy procedure.

When the garden hose runs clear you are finished.

Close the drain valve at the bottom of the tank and remove the garden hose.

Close the pressure relief valve at the top of the tank if it is still open, and turn the cold inlet valve back on.

Open a hot water faucet in your house, and let it run until no air bubbles come out.

Turn the heater back on, and with gas units re-light the pilot light if necessary.

Sources:http://homerepair.about.com/od/plumbingrepair/

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