68-0049—2
10
VR8205; VR4205
STARTUP AND CHECKOUT • MAINTENANCE • OPERATION
1. Turn off gas supply.
2. Set thermostat or controller above room temperature
to call for heat.
3. Watch for ignition spark or for glow at hot surface
igniter either immediately or following prepurge. See DI
module specifications.
4. Time the length of the igniter operation. See DI
module specifications.
Operation
The VR8205;VR4205 gas controls provide ON-OFF
manual control of gas flow. In the OFF position, gas flow to
the main burner is mechanically blocked. In the ON posi-
tion, gas flows to the main burner under control of the
thermostat, the direct ignition (DI) module, and the two
automatic main valves.
SYSTEM OPERATION WITH MODULE
When the thermostat calls for heat, the DI module is
energized. The module activates the first and second auto-
matic valves of the gas control, which allow gas to flow to
the main burner. At the same time, the DI module generates
a spark at the igniter-sensor to light the main burner.
The second automatic valve diaphragm, controlled by
the servo pressure regulator, opens and adjusts gas flow as
long as the system is powered. The servo pressure regulator
monitors outlet pressure to provide an even flow of gas to
the main burner. Loss of power (thermostat satisfied) de-
energizes the DI module and closes the automatic valves.
The system is ready to return to normal service when power
is restored through the thermostat.
If the igniter-sensor stops detecting a flame at the main
burner, the trial for ignition is restarted. On DI modules
with lockout timers, the automatic valves are de-energized
and ignition stops after the lockout period. On modules
without lockout timers, the trial for ignition continues
indefinitely.
If main burner flame is restarted successfully, operation
continues as described above. Gas control operation is
described in more detail below.
VALVE POSITION DURING THERMOSTAT OFF
CYCLE
The valve is positioned as shown in Fig. 10 when the:
• manual gas control knob is in the ON position.
• thermostat is not calling for heat.
The first automatic valve is closed. The second auto-
matic valve operator is de-energized, closing the channel to
the pressure regulator, and opening a channel to the under-
side of the second automatic valve operator valve dia-
phragm. The combination of spring pressure under the
second automatic valve diaphragm and lack of outlet pres-
sure holds the diaphragm firmly closed. Gas flow to the
main burner is blocked by both valves.
Regular preventive maintenance is important in applica-
tions that place a heavy load on systems controls, such as in
the commercial cooking and agricultural and industrial
industries because:
• In many such applications, particularly commercial
cooking, the equipment operates 100,000-200,000
cycles per year. Such heavy cycling can wear out the
gas control in one to two years.
• Exposure to water, dirt, chemicals and heat can dam-
age the gas control and shut down the control system.
The maintenance program should include regular check-
out of the gas control, see Startup and Checkout section,
and the control system as described in the appliance manu-
facturer literature.
Maintenance frequency must be determined individu-
ally for each application. Some considerations are:
• Cycling frequency. Appliances that may cycle 20,000
times annually should be checked monthly.
• Intermittent use. Appliances that are used seasonally
should be checked before shutdown and again before
the next use.
• Consequence of unexpected shutdown. Where the
cost of an unexpected shutdown would be high, the
system should be checked more often.
• Dusty, wet, or corrosive environment. Since these
environments can cause the gas control to deteriorate
more rapidly, the system should be checked more
often.
Gas valves exposed to high ammonia conditions; i.e.,
those used in greenhouses or animal barns, may fail in one
or two years. Contact your Honeywell sales representative
to request a gas valve with corrosion resistant construction.
The gas control should be replaced if:
• It does not perform properly on checkout or trouble-
shooting.
• The gas control knob is hard to turn.
• The gas controls is likely to have operated for more
than 200,000 cycles.
Maintenance
5. After the module locks out, open manual gas cock
and make sure no gas is flowing to the burner.
6. Set the thermostat below room temperature and wait
one minute.
7. Operate system through one complete cycle to make
sure all controls operate properly.
