Removing And Replacing The Gas Control Valve/Thermostat; Removing The Gas Control Valve/Thermostat; Replacing The Gas Control Valve/Thermostat; Draining And Flushing - A.O. Smith GCV300 Service Handbook

Residential fvir gas water heaters
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part on the pilot or pilot assembly.
If no spark is visible, check the
wire connections and make sure
that the electrode is not broken.
See also "Connections Check" (p.
11).
B. Replace the igniter if defective
(i.e.,
gas
control
thermostat
and/or
thermopile assembly). Dirt and
rust on the pilot or electrode tip
can prevent the igniter spark.
Wipe clean with a damp cloth
and dry completely. Rust can
be removed from the electrode
tip and metal surfaces by lightly
sanding with an emery cloth or
fine grit sandpaper.
Removing and Replacing
the Gas Control Valve/
Thermostat
IMPORTANT: This water heater has a
resettable thermal switch installed. Do
not attempt to disable or modify this
feature in any way. Use only factory
authorized replacement parts.
Removing the Gas Control
Valve/Thermostat:
1. Turn the gas control/temperature
knob
to the "OFF" position.
(Figure 6, page 9.)
2. Turn off the gas at the manual shut-
off valve on the gas supply pipe.
(Figure 1, page 6.)
3. Drain the water heater. Refer to
the "Draining and Flushing" section
and follow the procedure.
4. Disconnect the igniter wire from
the igniter lead wire. Use needle
nose pliers to disconnect the
red (+) and white (-) thermopile
wires. Disconnect the pilot tube
(7/16" wrench) and manifold
tube (3/4" wrench) at the gas
control valve/thermostat.
Figure 15 on page 17.
5. Disconnect
the
ground
union in the gas piping.
20 • Residential Standard Gas Water Heater Service Handbook
Figure 1, page 6.
the remaining pipe from the gas
control valve/thermostat.
6. To remove the gas control valve/
thermostat, thread a 4" section of
gas pipe into the inlet and use it to
turn the gas control valve/thermostat
valve/
(counterclockwise.) Do not use a
pilot/
pipe wrench or equivalent to grip
body. Damage may result, causing
leaks. Do not insert any sharp objects
into the inlet or outlet connections.
Damage to the gas control valve/
thermostat may result.
Replacing the Gas Control Valve/
Thermostat:
To replace the gas control valve/
thermostat, reassemble in reverse
order. When replacing the gas control
valve/thermostat, thread a 4" section
of gas pipe into the inlet and use it to
turn the gas control valve/thermostat
(clockwise). DO NOT OVER TIGHTEN;
damage may result.
• Be sure to use approved Teflon®
tape or pipe joint compound on the
gas piping connections and fitting
on the back of the gas control valve
that screws into the tank.
• Be sure to remove the pilot ferrule
nut from the new gas control valve/
thermostat.
• Turn the main gas supply on and
check the gas supply connections
for leaks. Correct any leak found.
Next, light the pilot and main
burner, then check the manifold
tube and pilot tube connections
for leaks. Correct any leak found.
Use an approved noncorrosive
leak detection solution. If such
a solution is not available, use
a mixture of hand dish washing
soap and water (one part soap to
15 parts water) or childrens' soap
bubble solution. Bubbles forming
indicate a leak.
See
• Be sure tank is completely filled
with water before lighting and
joint
activating the water heater. Follow
See
Disconnect
the "Lighting Instructions" on the
front of the water heater.
TEFLON® is a registered trademark of
E.I. Du Pont De Nemours and Company

Draining and Flushing

WARNING! Hot Water Discharge
Hazard:
• Keep
pressure relief valve discharge.
• Temperature
available.
• Read
information on a safe temperature
setting.
It is recommended that the tank be
drained and flushed every 6 months
to remove sediment which may build
up during operation. The water heater
should be drained if being shut down
during freezing temperatures. To drain
the tank, perform the following steps:
1. Turn off the gas to the water heater
at the manual gas shut-off valve.
2. Open a nearby hot water faucet
until the water is no longer hot.
3. Close the cold water inlet valve.
4. Connect a hose to the drain valve
and terminate it to an adequate
drain or external to the building.
5. Open the water heater drain valve
and allow all of the water to drain
from the tank. Flush the tank with
water as needed to remove sediment.
6. Close the drain valve, refill the tank,
and restart the water heater as
directed in the lighting instructions.
(The
posted on the front of the water
heater.)
heater is full of water before you
light the pilot.
If the water heater is going to be
shut down for an extended period,
the drain valve should be left
open. IMPORTANT: Condensation
may occur when refilling the tank and
should not be confused with a tank
leak.
clear
of
temperature/
limiting
valves
are
instruction
manual
for
lighting
instructions
are
Ensure that the water

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