System Basics; Honeywell® Gas Control Valve/Thermostat; Gas Pressures; Temperature Settings - A.O. Smith GCV300 Service Handbook

SYSTEM BASICS

Honeywell® Gas Control
Valve/Thermostat
Water heaters covered by this handbook
are equipped with Honeywell gas
control valve/thermostats.
• The Honeywell valve
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).
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
Figure 2B
error codes, see "Lighting the Pilot /
Diagnostic Flash Codes" on page 9.
uses a

Gas Pressures

See
Ensure that the following pressures are
observed and maintained:
Table 1. GAS PRESSURES
GAS MAXIMUM
PRESSURE
NAT 14 InWC
LP 14 InWC
Min. Supply Pressure: See Rating Plate.
Temperature Control Knob
Temperature control ranges:
Pilot
Figure 2.
MANIFOLD
SUPPLY GAS
PRESSURE
5.0 InWC
(± 0.4 InWC)
10.0 InWC
(± 0.5 InWC)
*
* Some models do not
Residential Standard Gas Water Heater Service Handbook • 7
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 Se 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.