Back to main page Atlanta Appliances repair, Inc.

Gas Water Heaters

water is heated. They use liquefied petroleum gas (LP or LPG) or natural gas to heat

the water. The tank is constructed in such a way that it allows for a vent (chimney)

up the middle of the tank, along with a gas burner on the bottom of the tank to heat the

water (Figure 17-1). The thermostat that controls the water temperature and gas flow is

mounted on the outside of the tank, with the temperature probes inserted into the tank to

sense the water temperature. A temperature and pressure-relief valve, which is mounted on

the outside of the tank, is a device applied to a water heater that will open to pass water or

steam if excessive pressure or temperature occurs in the water heater tank.

Gas water heaters are available in many different sizes. When purchasing a gas water

heater, it is important to specify the type of gas fuel that will be used to heat the water.

Principles of Operation

The gas water heater fills up in the same way as an electric water heater. Water enters the

cold-water inlet port through a dip tube, filling the tank from the bottom up. Once the tank

is full of water, the gas supply is turned on and the consumer or technician can begin the

process of lighting the burner according to the manufacturer’s use and care manual. Once

the pilot light is lit, the thermocouple, which is near or in the gas flow, will begin to heat

up and send a signal to the gas combination valve to open the gas inlet to the pressure

regulator section of the combination control valve. At the same time, the thermostat senses

the cold water and sends a signal to the combination control to actuate a lever from within

the pressure regulator to open the gas valve, allowing the gas to enter the burner for

ignition. While the gas flames are heating the water, the thermostat begins monitoring the

water temperature. When the water temperature reaches a preset temperature, a signal will

be sent to the combination valve to Shutoff the gas flow.

Safety First

maintain or repair any gas water heaters. Any improper installation, preventive maintenance,

or repairs could create a risk of personal injury, death, or property damage.

479

CHAPTER

If you do not fully understand the preventive maintenance or repair procedures in this

chapter, or if you doubt your ability to complete the task on your gas water heater, please

call your service manager.

These precautions should also be followed:

full of water.

FIGURE 17-1

Exploded view of a

gas water heater.

PART VI

manufacturer’s recommendations.

connections, plumbing, ventilation, and placement of the tank be done by qualified

personnel. Observe all local codes and ordinances for gas fuels, venting, plumbing,

and installation procedures.

Before continuing, take a moment to refresh your memory concerning the safety procedures

in Chapter 2. In addition, please follow the manufacturer’s recommendations for safety as

outlined in the use and care manual.

Gas Water Heaters in General

Much of the troubleshooting information in this chapter covers gas water heaters in general,

rather than specific models, in order to present a broad overview of service techniques. The

pictures and illustrations that are used in this chapter are for demonstration purposes only,

to clarify the description of how to service these heaters. In no way do they reflect on a

particular brand’s reliability.

Gas Water Heater Maintenance

assist you in performing the maintenance procedures:

1. A visual inspection must be made to the following components:

fumes from entering the home. Check the venting system for leakage, corrosion,

obstructions, sooting, and rust forming on top of the water heater. If any of these

conditions are present, you must take action to correct these problem areas to

protect the health and lives of the people living in the home. Most important,

check the fitting (vent cap) on the end of the vent pipe for obstructions.

A properly designed and working vent system will convey the combustion gases

from the water heater environment to the atmosphere outside of the home.

It will also protect the home from fire hazards due to overheating of walls and

other surfaces, prevent condensation of hot combustion gases, and provide clean

air circulation and adequate oxygen supply for the water heater.

Check for adequate air supply to the area in which the water heater is located.

A gas water heater will consume about 12.5 cubic feet of air (at sea level) for

every 1000 BTUs of heat generated.

If your inspection reveals that the burner, pilot, or base assemblies need cleaning,

turn off the gas supply and remove the burner and pilot assemblies for cleaning.

Some models have a removable screen at the bottom of the tank that keeps dust,

lint, and oils from entering the combustion chamber. This filter screen must also

be cleaned.

and debris. Make sure that combustible materials are removed completely from

the area.

2. Inspect the temperature and pressure-relief valve (T&P) for leaks. If it is leaking

water, you must replace it. Make sure that the valve is connected to a drain line that

terminates to a drain or to the outside of the residence. Next, you will manually

operate the T&P valve and check for proper operation. Be careful—the discharged

water is very hot. Lift the T&P lever gently and then release it—the lever should

return to its normal closed position. If the water is still leaking out of the valve after

you release the lever, replace the valve.

3. Once a year, the water heater tank should be drained and flushed out. This procedure

will increase the life expectancy of the tank by removing the unwanted sediment.

Before you begin draining the tank, turn off the gas supply to the water heater. To

drain the water heater tank, turn off the water supply to the tank. Connect a garden

hose to the draincock, and open the valve. To increase the water flow draining out

of the tank, open the hot water faucet—this will increase the flow of water draining

out of the tank. When you are ready to refill the tank, close the draincock, turn on

the water supply to the water heater, and begin to refill the tank.

Leave the closest hot water faucet open during refilling; the air that is trapped in the

tank will escape through the hot water faucet. When all of the air is out of the tank and

water lines, close the hot water faucet. Go to all of the other hot water faucets, and open

them to remove the air in the lines. Close all water faucets. Now you are ready to turn on

the gas supply to the water heater. Light the pilot light according to the manufacturer’s use

and care guide for the model you are servicing.

Thermal Expansion

When water is heated in the water heater tank, it will expand. There is a physical law that

states that as the water temperature rises, the water will expand in volume. For example,

heating 40 gallons of water to the temperature setting on the thermostat will cause it to

expand to 40.5 gallons when the temperature is reached. In the old days, before backflow

preventers, water meter check valves, and pressure reducing valves, the excess water

flowed back to the city main water supply where it was dissipated. Today, with the added

controls and safety valves, the water cannot return to the city water supply. The water in the

tank is in a “closed loop system” and has nowhere to go. The thermal expansion of the

heated water causes a serious problem to the tank and the residence. The internal pressures

in the water heater tank during recovery periods can stress the tank, causing the tank welds

and fitting connections to the tank to weaken and fail, in turn causing flooding in the

residence and possibly even bodily injury.

PART VI

As the pressure builds up in the water heater tank, the temperature pressure relief valve

(T&P valve) will open and the excess water will be released from the water heater tank,

either on the floor or drained to the outside of the residence. Even though the T&P valve

opens during every recovery period, this action will weaken the tank and shorten its life.

A good indicator of thermal expansion is when the T&P valve releases about one cup of

water for every ten gallons of water in the tank for each heating period.

The best way to control thermal expansion in a water heater tank is to install a thermal

expansion tank, shown in Figure 17-2. The thermal expansion tank will accept the excess

water and pressure away from the water heater tank, store it, and return the excess water

back to the water heater tank in the “closed loop system” as the water is used. This will

T&P

discharge

line

Thermal

expansion

tank

Venting

nominal to

local code

Hot out of

ixtures

Cold water

inlet

Gas

line

Isolation

shut-off

valve

Union

FIGURE 17-2

A thermal expansion

tank installed to

prevent water heater

damage and looding.

prolong the life of the water heater tank. Also, the expansion tank will prolong the life of the

temperature pressure relief valve. Figure 17-3 illustrates that water at 70º F in a water heater

tank, with no pressure on the tank, will begin to rise in pressure when heated.

Water Hammer

When the hot or cold water valve is turned off quickly, a loud banging noise can be created.

This noise is called a water hammer. If you close the water valve slowly, you will not hear a

water hammer noise. A water hammer noise occurs when the water in a closed loop system

comes to an abrupt stop at the water valve; a high-pressure shockwave reverberates within

the piping system until the energy has been spent in frictional losses.

To prevent a water hammer condition, a water hammer arrestor device will have to be

installed. These are designed so the water in the closed loop system will not contact the air

cushion in the arrestor. This phenomenon is not a water heater issue; it is a plumbing issue.

If a water hammer arrestor needs to be installed, contact a certified plumber.

Negative Air Pressure

Air pressure in a residence is affected by different forces, such as blowing wind, forced-air

furnaces, clothes dryers, bathroom fans, range hoods, fireplaces, ceiling fans, and even the

central vacuum cleaner. When the air pressure inside a residence is greater than the outside

pressure, it’s called positive pressure. When the pressure in a residence is less than the

outside pressure, it’s called negative pressure. Any device that can pull air out of a residence

can create a negative pressure inside.

Over the past two decades, construction techniques have improved the energy efficiency

of buildings, making them tighter and resistant to air leaks. The tighter the building, the

greater potential for negative air pressure. This might leave you with a problem: combustion

and ventilation air is not able to infiltrate into the building and combustion appliances and

heating furnaces will be starved for air. There may be no air left in the building to operate

the other devices such as exhaust fans. When this happens, the negative air pressure inside

600

500

400

300

200

Pressure Psig

150

100

0

65 70 75 80 85

Temperature - °F

T&P Valve activates here at @150 psi

Water

90 95 100

This igure points out

the danger of what

happens to the water

pressure when heated

in a closed loop

system.

PART VI

the building draws air in through every crack and crevice it can find to equalize the inside

pressure.

Under normal conditions with positive air pressure in the building, the gas water heater

will be able to vent the combustible by-products (flue gases) and the heat from the gas

burner through the vent system to the outside of the building. When you have negative air

pressure in the building, the combustible by-products (flue gases) and the heat from the

burner will not vent to the outside. Instead, the vent system will act as a fresh air intake

source. The flue gases and heat will stay in the structure, causing poor water heater

performance and harmful gases to the occupants. Symptoms of negative air pressure

problems are:

The only places to find negative air pressure in a residence are the kitchen and laundry

area. In the kitchen there might be an exhaust fan over the range venting air to the outside

of the structure. In the laundry area, a gas dryer will vent moist air to the outside of the

building.

Draft Test

To check and see if the gas water heater is venting properly, perform a draft test (Figure 17-4).

This test only applies to a natural vent system, and does not apply to the forced vent system

water heater. Symptoms of a blocked vent include:

top of the tank and directly under and around the draft hood.

To conduct a draft test, perform the following:

1. Turn the thermostat up high on the combination valve until the burner comes on.

2. Wait 3 to 5 minutes until the venting system gets warm.

3. Place a smoke source halfway between the bottom of the draft hood and the top of

the water heater. A smoke source can be a match or an incense stick.

4. Observe how the smoke behaves. If the smoke is drawn into the vent system, then

the vent system is okay. If the smoke blows toward you, then there is a venting

problem that has to be corrected.

5. When you complete the test, return the thermostat back to its original position

(around 120º F).

Step-by-Step Troubleshooting by Symptom Diagnosis

In the course of servicing an appliance, don’t tend to overlook the simple things that may be

causing the problem. Step-by-step troubleshooting by symptom diagnosis is based upon

diagnosing malfunctions, with their possible causes arranged into categories relating to the

operation of the water heater. This section is intended only to serve as a checklist to aid you

in diagnosing a problem. Look at the symptom that best describes the problem that you are

experiencing with the water heater and then proceed to correct the problem.

Gas Odors

1. Check the pilot light.

2. Check for a gas leak in the supply line.

3. Check the ventilation system.

The Burner Will Not Ignite

1. Make sure that the gas supply to the water heater is turned on.

2. Check the gas line for debris. Also, check the pilot line for debris.

3. Check the line to the burner for a blockage. If blocked, locate the source and correct.

4. Check the thermostat setting. It may be set too low.

5. Test the value of the thermocouple; replace if necessary.

6. Test the thermostat; replace if necessary.

7. Check the installation and fresh air supply.

The Pilot Will Not Light or Stay Lit

1. Make sure that the gas supply to the water heater is turned on.

2. Check the gas pressure to the water heater.

Vent

Draft hood

Hot Cold

FIGURE 17-4

To determine if the

vent system is

working in an

atmospherically

vented gas water

heater, perform

a draft test.

PART VI

3. Check for air or debris in the lines. Purge the gas line.

4. Check the pilot line and orifice for debris.

5. Test the thermocouple, thermostat, and ignitor. Replace if necessary.

6. Check for drafts that can extinguish the pilot.

7. Check the intake air for obstruction. This is the air that is needed for combustion.

8. Check for flammable vapors.

Not Enough Hot Water

1. Check the thermostat; it might be set too low.

2. Check the installation for correct piping connections. Is the tank adequate for the

size of the household and usage?

3. Check the home for hot water leaking from the faucets. Did you notice any wasting

of hot water? If so, speak to the consumer.

4. Where are the water pipes located? Are the pipes exposed to the elements? Are they

insulated? Check on the length of the piping.

5. Check the tank for sediment or lime. You may have to flush out the tank.

Slow Hot Water Recovery

1. Check for insufficient secondary air supply. Check the venting system and the burner.

2. Check the gas pressure. Is the type of gas correct for the water heater?

3. Check the thermostat setting. Is it out of calibration?

4. If this is a new installation, check the piping connections.

5. Check for wasting of water.

6. Is the water heater the correct size for the household?

The Burner Flame Is Too High

1. Is the orifice too large? You can change the orifice and retest the burner.

2. Check for sufficient secondary air supply. Check the venting system and the burner.

The Flame Burns at the Orifice

1. Check the thermostat. Replace if necessary.

2. Check the gas pressure to the water heater.

The Pilot Flame Is Too Small

1. Check the pilot line and orifice for debris.

2. Check the gas pressure to the water heater.

The Burner Flame Floats and Lifts Off the Ports

1. Is the orifice too large? You can change the orifice and retest the burner.

2. Check for high gas pressure.

3. Check the flue and burner. Locate the source and correct the problem.

4. Check for drafts that can blow the flame off the burner.

A Yellow-Lazy Burner Flame

1. Check for sufficient secondary air supply.

2. Check the gas pressure.

3. Check the venting system. Is the flue clogged?

4. Check the burner line for debris.

5. Check the water heater installation. Is the tank installed in a confined space?

6. Check the burner orifice for obstruction.

The Formation of Soot (Smoke and Carbon)

1. Check for sufficient secondary air supply.

2. Check the flue way, flue baffle, and burner.

3. Test the draft hood for proper ventilation.

4. Check for a yellow-lazy burner flame.

5. Check for low gas pressure to the water heater.

6. Check the thermostat. Replace if necessary.

7. Is the water heater installed in a confined space?

Condensation

Check the thermostat setting. Is it set too low?

The Water Has an Odor

Check for sulfides in the water. If necessary, replace the anode.

The Water Heater Jacket Is Discolored Above the Combustion Area

1. Check that the burner orifice is the proper size.

2. Is the flue clogged?

3. Check for high gas pressure.

Combustion Odors

1. Check for sufficient secondary air. Check the flue way, flue baffle, and the burner.

2. Is the flue clogged?

3. Is the water heater installed in a confined space?

Repair Procedures

Each repair procedure is a complete inspection and repair process for a single water heater

component. It contains the information you need to test a component that may be faulty

and to replace it, if necessary.

PART VI

Burner/Manifold Assembly

The typical complaints associated with the burner/manifold assembly are:

the gas flow if the temperature in the combustion chamber exceeds its limit.

To handle this problem, perform the following steps:

come on? Check the thermal cutoff device. What color is the burner flame? Does the

burner/manifold assembly need cleaning?

the water heater. Is the gas supply turned on? Is the water heater installed properly?

Is there sufficient air supply? Is the surrounding area clear of debris?

the supply of gas to the water heater. Turn the gas control knob on the combination

gas control to the off position (Figure 17-5a). See the use and care guide for the

model you are servicing.

the skirt (see Figure 17-5a). At the combination gas control, disconnect the following:

thermocouple, ignitor wire from the ignitor button, pilot tube, and the manifold

tube (Figure 17-5b). Gently push down on the manifold tube to free the manifold,

thermocouple, and pilot tube. Next, carefully remove the burner/manifold assembly

from the burner compartment. Try not to damage any of the internal parts.

water heater, you can inspect the burner and clean it. Disassemble the burner from

the manifold assembly by removing the two screws that secure it to the manifold

(Figure 17-6). To clean the burner, use soap and hot water, rinse, and let it dry. Clean

the remainder of the manifold assembly with a brush, and blow off any debris from

the flame trap. Inspect the pilot tube and the manifold tube for a blockage. Before

reinstalling the burner/manifold assembly, clean out the combustion chamber

(Figure 17-7) with a shop vacuum, making sure that you remove all of the loose

debris. Some models are manufactured with a flame arrestor to prevent flames from

escaping the combustion chamber. This component must also be cleaned with a

vacuum to remove debris.

just reverse the disassembly procedure. Before you get started, inspect the gaskets

for wear and tear, and replace them if necessary. Reconnect the pilot tube, manifold

tube, thermocouple, and ignitor wire. Next, turn on the gas supply and light

Gas valve/thermostat

Piezo ignitor button

Pilot tube

Two piece wire

connector

Manifold screw (2)

Manifold

door

Viewport

Manifold

tube

Thermocouple

Manifold

tube

Pilot

tube

Ignitor

Thermocouple

The combination

control valve. The

ignitor, thermocouple,

manifold tube, pilot

tube, and ignitor will

have to be

disconnected in order

to remove the valve

assembly.

PART VI

Thermocouple

retainer clip Pilot assembly

Pilot bracket

Manifold

door

gasket

Viewport

Thermocouple

Manifold

tube

Pilot tube

Ignitor wire

Manifold door

assembly

Two piece wire

Burner connector

Thermocouple

Manifold door

assembly

Burner Pilot assembly

Screws

Manifold

tube

Pilot tube

the burner according to the manufacturer’s recommendations for the model you

present. If no leaks are found, you are ready to reinstall the outer door.

Tab

Flame-trap Bracket

FIGURE 17-7

The burner/manifold

assembly located in

the combustion

chamber.

by letting the hot water run for a while and then shutting it off. The water heater

will begin cycling. Inspect the flame—it should be a blue flame. Adjust the air shutter

as needed. On some models, you will have to remove the burner/manifold assembly

to adjust the air shutter.

Combination Control Valve

The combination control valve consists of a gas pressure regulator valve, thermostat, and

ignitor. The combination control valve also has a gas cutoff device incorporated into the valve

to shut off the gas supply in the event that the thermostat fails. In Figure 17-8, the thermostat

does not have numbered temperature markings only notches that indicate 60 degrees and up.

The typical complaints associated with the combination control valve are:

temperature in the combustion chamber exceeds its limit.

To handle this problem, perform the following steps:

water temperature and the thermostat setting. Does the burner cycle at the

predetermined temperature? Check the thermal cutoff device. Check for sooting.

Can you shut off the burner with the thermostat control knob?

PART VI

WARM

CAUTION

HOT

VACATION

Red Button Gas Cock Knob

120°F. (Approx.)

60°F. (Approx.)

70°F. (Approx.)

80°F. (Approx.)

90°F. (Approx.)

100°F. (Approx.)

110°F. (Approx.)

Index

WARNING

Read all instructions

before lighting

Index

FIGURE 17-8

The notches on the

thermostat dial

indicate approximately

10-degree increments

starting from 60º F to

the irst index mark as

shown.

the water heater. Is the water heater installed properly? Is there sufficient air supply?

Is the surrounding area clear of debris? Is the ventilation system clear of debris?

the supply of gas to the water heater. Turn the gas control knob on the combination

gas control to the “off” position (see Figure 17-5a). See the use and care guide for

the model you are servicing.

valve according to the use and care guide for the model you are servicing. Turn off

the main gas supply to the water heater. Before you can remove the control valve,

you first have to drain the water heater tank. To drain the water heater tank, turn

off the water supply to the tank. Connect a garden hose to the draincock, and open

the valve. To increase the water flow draining out of the tank, open the hot water

faucet—this will increase the flow of water draining out of the tank. While the tank

is draining, disconnect the ignitor wire from the ignitor, and remove the ignitor

button and bracket. Remove the manifold tube and pilot tube, and disconnect the

thermocouple (see Figures 17-5a and 17-5b). Next, disconnect the ground joint

union located between the gas shutoff valve and the combination valve. Disconnect

the remaining pipe from the combination gas control valve. When the water heater

tank is empty, you are ready to remove the control valve. Turn the valve

counterclockwise and remove it from the tank.

just reverse the order of disassembly. Make sure that you use approved pipe joint

compound or Teflon yellow tape on the pipe connections (according to local codes)

and on the threads of the control valve before you install the valve into the water

heater tank. This will prevent water from leaking out of the tank. Close the draincock

and turn on the water supply to the tank, allowing it to fill up. Keep a faucet open near

the tank to allow air to escape from it. As for the gas lines, you will perform a leak

check using a chloride-free soap and water solution when the gas supply is turned

back on. Finally, check for any water leaks before lighting the burner.

Thermocouple

A thermocouple is a measuring device consisting of two dissimilar metals, which produces

a low DC voltage when heated by a gas pilot flame that is measured in millivolts. The average

output voltage for a single thermocouple is between 20 and 30 millivolts.

The typical complaints associated with the thermocouple are:

To handle this problem, perform the following steps:

burner come on? Check the pilot light. Is it lit?

the water heater. Is the water heater installed properly? Check the gas supply line.

Is it turned on? Is there sufficient air supply? Is the surrounding area clear of debris?

the skirt (see Figure 17-5a). At the combination gas control, disconnect the following:

thermocouple, ignitor wire from the ignitor button, pilot tube, and the manifold tube

(see Figure 17-5b). Gently push down on the manifold tube to free the manifold,

thermocouple, and pilot tube. Next, carefully remove the burner/manifold assembly

from the burner compartment. Try not to damage any of the internal parts. Remove

the thermocouple two-piece connector by removing the retainer clip that secures

the thermocouple connector to the manifold door (Figure 17-9). Disconnect the

thermocouple from the pilot bracket (Figure 17-10).

of disassembly. Insert the new thermocouple into the bracket holes until it clicks

into place. Now you are ready to reinstall the burner/manifold assembly and test.

Ignitor

The typical ignitor that is used on gas water heaters is the piezoelectric ignitor (Figure 17-11).

When the button on the ignitor is pushed down, it produces a spark at the burner.

The typical complaint associated with the ignitor is that the burner will not light or

remain lit. To handle this problem, perform the following steps:

burner come on? Check the pilot light. Is it lit? Turn off the gas supply and observe

the ignitor electrode when activating the ignitor. Do you see a spark at the ignitor?

PART VI

the water heater. Is the water heater installed properly? Check the wiring

connections and wiring. Is the ignitor electrode broken?

the skirt (see Figure 17-5a). At the combination gas control, disconnect the following:

thermocouple, ignitor wire from the ignitor button, pilot tube, and the manifold tube

(see Figure 17-5b). Gently push down on the manifold tube to free the manifold,

thermocouple, and pilot tube. Next, carefully remove the burner/manifold assembly

from the burner compartment. Try not to damage any of the internal parts. Remove

the ignitor electrode from the pilot bracket (Figure 17-12a and b).

Thermocouple

Two piece

wire connector

Notice:

Thermocouple

must not be bent

in this location.

Ignitor wire

Retainer clip

Manifold

door

FIGURE 17-9

The thermocouple

assembly. Do not

bend the

thermocouple as

indicated; it has an

internal thermal fuse

that could be

damaged.

Pilot bracket

Thermocouple

Pilot

0.125 in.

Tip Electrode

FIGURE 17-10

The thermocouple

bracket assembly. The

electrode must be

positioned 0.125

inches from the pilot.

FIGURE 17-11

A piezoelectric ignitor.

This type of ignitor is

used to ignite the gas

burner.

FIGURE 17-12

(a) The natural gas

ignitor assembly. (b)

The LP gas ignitor

assembly.

Ignitor

button

Wire to

electrode

Snap-on

connector

Pilot bracket

Thermocouple

Pilot

0.125 in.

Tip Electrode

Ignitor

button

Thermocouple

0.125 in.

Tip

Pilot

Electrode

Pilot bracket

Wire to

electrode

Snap-on

connector

(a)

(b)

PART VI

disassembly. When positioning the ignitor electrode in the pilot bracket, the spark

gap should be 0.125 inches. Reinstall the burner/manifold assembly and test.

Water Heater Leakage Inspection Points

A technician must check the following areas for leakage when servicing the water heater

(Figure 17-13):

A. Check the draft hood for condensation. Water vapor that has formed from combustion

products is an indication of a problem in the vent system. If this problem is not

corrected, the top of the water heater will begin to rust.

B. On humid days, condensation may appear on the pipes and connections.

C. Check the anode rod fitting for leakage.

D. Check for leakage at the temperature and pressure-relief valve and piping. The

leakage could be from thermal expansion or high water pressure to the household.

If there is a steady stream of water coming from the valve, the temperature and

pressure-relief valve may be defective.

E. Check for leakage from the temperature and pressure-relief valve fitting at the tank.

F. The drain valve may be leaking. Check if the valve is slightly open.

G. Check for leakage from the drain valve fitting at the tank.

H. Check for leakage in the combustion chamber. Combustion products that contain

water vapor could form droplets in that area. When cold water enters the tank,

condensation may form droplets in that area, too. These droplets can fall on the

burner/manifold area, causing damage to the component. In addition, the

droplets can run onto the floor. This usually happens on new installation startups.

I. Check the rim around the outside of the water heater tank for leakage, the water

heater bottom, and on the floor. Check for leakage at all pipe connections and at the

temperature and pressure-relief valve. Check and see if the temperature and

pressure-relief valve discharge line is directed over a drain or runs to the outside of

the residence. In some cases, I found the discharge line was draining on the floor

and was not piped correctly.

Other possibilities for water leakage around the water heater tank can come from other

appliances (for example, an automatic washer or air conditioner), water lines, and ground

water seepage.

Diagnostic Charts

The following diagnostic flowchart (Figure 17-14) will help you to pinpoint the likely causes

of the problem. See also Figures 16-25 and 16-26 and Table 16-1.

Table 17-1 illustrates how to figure the hot water recovery rate by hand when you know

the BTU input located on the data tag:

Hourly input (BTU’s)

11.0 x temperature rise ºF

A

B C

E

D

B

G

H

F

I

FIGURE 17-13

Leakage inspection

points on a gas water

heater.

PART VI

Is the pilot light lit?

No Check gas

pressure.

No

Yes

Yes

No

Is the thermostat

set at the proper

temperature?

With the gas supply on

light the pilot.

No

No

Replace thermostat, thermocouple,

or ignitor if necessary.

Is the burner

on?

Perform annual

maintenance.

Adjust the thermostat. Replace thermostat.

Check the thermocouple,

thermostat, and ignitor.

Replace defective

component.

Check the gas lines for

debris.

Clean, locate source, and

correct.

Check ventilation system

and fresh air intake.

Check water heater

installation.

Clean, locate source, and

correct.

Make sure tank installation

is not in a confined space.

INPUT

BTU 40oF 50oF 60oF 70oF 80oF 90oF 100oF 110oF 120oF 130oF 140oF

Formulas and Facts

1 gallon of water weighs 8.33 lbs

1 gallon of water has a volume of 231 cubic inches

1 cubic foot of water weighs 62.38 lbs and contains 7.48 gallons of water

100 feet of ¾-inch copper pipe contains 2.5 gallons of water; 1-inch pipe contains 4.3 gallons

8.33 BTU will raise 1 gallon of water 1°F at 100 percent efficiency (electricity)

11 BTUs are required to raise 1 gallon of water 1°F at 75 percent efficiency (gas)

3412 BTU equals 1 kilowatt hour (Kwhr)

1 Kwhr will raise 410 gallons of water 1°F at 100 percent efficiency

1 BTU × 0.293 = watts

1 KW = 1000 watts

2.42 watts are required to raise 1 gallon of water 1°F

1 Kwhr will raise 10.25 gallons of water 40°F at 100 percent efficiency

1 Kwhr will raise 6.8 gallons of water 60°F at 100 percent efficiency

1 Kwhr will raise 5.1 gallons of water 80°F at 100 percent efficiency

1 Kwhr will raise 4.1 gallons of water 100°F at 100 percent efficiency

INPUT

BTU 40oF 50oF 60oF 70oF 80oF 90oF 100oF 110oF 120oF 130oF 140oF

PART VI

Electric Water Heaters

Energy Costs:

Kwhr × fuel costs = energy costs

If I use 100 kilowatt hours of electricity, how much will it cost if each kilowatt hour costs

$.05?

100 × .05 = $5.00

To obtain gallons per hour (GPH) recovery:

Watts

I have a 30-gallon electric heater, nonsimultaneous operation, 4500 watt elements. What is

the recovery GPH if my cold water is 40° F and my thermostat is set to 120° F?

4500

= 23 gallons per hour

Temperature Rise (°F)

Watts

I have a 30-gallon electric heater, nonsimultaneous operation, 4500 watt elements. What is

the maximum temperature rise if the heater can recover 23 gallons per hour?

4500

= 80 degrees temperature rise

Gas Water Heaters

Energy Costs:

Cubic feet × fuel costs = energy costs

If I use 100 cubic feet of gas, how much will it cost if each cubic foot costs $.075?

100 × .075 = $7.50

To obtain gallons per hour (GPH) recovery:

Hourly Input (BTUs)

I have a 30-gallon gas heater rated at 40,000 BTUs. What is the recovery GPH if my cold

water is 40° F and my thermostat is set to 120° F?

40,000

= 45 gallons per hour

Temperature Rise (°F)

Hourly Input (BTUs)

I have a 30-gallon gas heater rated at 40,000 BTUs. What is the maximum temperature rise if

the heater can recover 45 gallons per hour?

40,000

= 80 degrees temperature rise

Formula for Mixing Hot Water

M – C = Percent of hot water required to produce desired mixed water temperature

H – C

where M = mixed water temperature, C = cold water temperature, H = hot water temperature.

For example: How much of a shower is hot water and how much is cold water? My shower

temperature is 105° F, my water heater thermostat is set on 120° F, and the cold water inlet

temperature is 50° F.

105 – 50 = 55 = 79% of the shower is 120° hot water

120 – 50 = 70

This formula for mixing hot water is important when explaining to a customer why

there might not be enough hot water when the water heater is functioning properly.

Electric Working Formulas That Apply to Water Heaters

To verify circuit breaker or amperage draw on the water heater:

Amperage draw =

Watts

Voltage

Amperage draw =

4500 watts (heating elements shown on rating plate total)

240 volts (shown on the rating plate)

Amperage draw = 18.8 amps (circuit breaker should be 20% higher or 25 amp breaker)

Now that you have solved amperage, what is the resistance (Ohms) of the heating element?

(If a heating element has no resistance, then it is open, or broken.)

Resistance (Ohms) =

Voltage

Amperage

Resistance (Ohms) =

240 volts (shown on the data rating plate)

18.8 (answer from previous problem)

Resistance = 12.8 Ohms

Help on the Internet

To obtain additional technical help or information on selecting a gas water heater, you can

go to the following websites:

http://www.aceee.org/consumerguide/topwater.htm

http://www.aosmith.com/