A.O. Smith GVR300 - System Basics; Honeywell Gas Control Valve;Thermostat; Gas Pressures; Temperature Settings

Residential Standard Gas Water Heater Service Handbook • 7
BASICS
Honeywell® Gas Control
Valve/Thermostat
Water heaters covered by this handbook
are equipped with Honeywell gas
control valve/thermostats.
• The Honeywell valve uses a
thermopile instead of a thermocouple
as did previous designs.
• Heat on the thermopile generates
750 to 900 millivolts (open circuit).
• When heated by the pilot and
connected to the Honeywell control,
the thermopile generates at least
350 millivolts (closed circuit). This
voltage opens the power head
in the control, allowing gas to
flow. It also powers the onboard
diagnostics (status light). See
Figure 2.
• The Honeywell valve uses a standard
push-button piezo igniter. See “Spark
Igniter” in Figure 2B.
• Status codes are printed on the face
of the control for easy reference
(Figure 2B.)
• The LED status light shows the
current status of the control as well
as possible error codes for easy
diagnosis. For more information on
error codes, see “Lighting the Pilot /
Diagnostic Flash Codes” on page 9.
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Thermopile
Pilot
Figure 2.
Gas Pressures
Ensure that the following pressures are
observed and maintained:
Table 1. GAS PRESSURES
GAS MAXIMUM
SUPPLY
PRESSURE
MANIFOLD
GAS
PRESSURE
NAT 14 InWC 5.0 InWC
(± 0.4 InWC)
LP 14 InWC 10.0 InWC
(± 0.5 InWC)
Min. Supply Pressure: See Rating Plate.
The gas control valve\thermostat also
includes a temperature limiting ECO
(Energy Cut Off) system. This system
will shut off the water heater if the
water temperature becomes excessive.
Should the water temperature get
too high, the main burner and pilot
will shut off automatically. Once the
pilot is relit, the status light will flash
a code (4 flashes), indicating an over-
temperature condition. See “Lighting
the Pilot / Diagnostic Flash Codes” on
page 9 for more information.
NOTE: Honeywell is a registered trademark
of Honeywell International, Inc.
Temperature Seƫ ngs
The water temperature setting can be
adjusted from 55°F to 155°F. Simply
turn the gas control/temperature Knob
to the desired setting/temperature.
See Figure 3.
NOTE: The temperatures indicated are
approximates. The actual temperature
of the heated water may vary.
SYSTEM BASICS
Figure 2B
Temperature Control Knob
*
Temperature control ranges:
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* Some models do not
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