9
68-0150
VR8405
STARTUP AND CHECKOUT • MAINTENANCE • OPERATION
1. Turn off knobs on entire gas control.
2. Set thermostat or controller above room temperature
to call for heat.
3. Watch for ignition spark or 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.
5. After the module locks out, open gas control knobs
and make sure there is no gas flow to the main burner.
6. Set thermostat below room temperature and wait
one minute.
7. Operate system through one complete cycle to make
sure all controls operate properly.
Maintenance
WARNING
FIRE OR EXPLOSION HAZARD
CAN CAUSE PROPERTY DAMAGE,
SEVERE INJURY, OR DEATH.
Do not disassemble the gas control or either valve.
They contain no replaceable components. Attempted
disassembly or repair can damage the gas control.
Regular preventive maintenance is important in applica-
tions such as commercial cooking, agricultural and indus-
trial operations that place a heavy load on system controls
because:
• In many applications, particularly commercial cook-
ing, the equipment operates 100,000 to 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 entire gas control; see Startup and Checkout
section. To check out the control system, see the appliance
manufacturer literature. Maintenance frequency must be
determined individually for each application. Some consid-
erations are:
• Cycling frequency. Appliances that may cycle 100,000
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.
If the gas controls will be exposed to high ammonia
conditions; e.g., those used in greenhouses or animal barns,
contact your Honeywell sales representative to request a
gas control with corrosion resistant construction.
The entire gas control should be replaced if:
• It does not perform properly during checkout or
troubleshooting.
• The gas control knobs are hard to turn.
• The gas control is likely to have operated for more
than 200,000 cycles.
Operation
The VR8405 gas controls provide ON-OFF manual con-
trol of gas flow. When both knobs are in the OFF position,
main burner gas flow is prevented. When both knobs are in
the ON position, main burner gas flow is under control of
the thermostat, the direct ignition module, and the two auto-
matic valve operators of each valve.
The VR8405 gas controls consist of two parallel valves
on a die-cast manifold to provide high capacity. The indi-
vidual valves operate in unison to regulate gas flow. The
following information describes how each individual valve
operates as well as how they interact.
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 controls which allows main burner
gas flow. At the same time, the DI module generates a
spark at the igniter-sensor to light the main burner.
The second automatic valve diaphragm of each valve,
controlled by its servo pressure regulator, opens and adjusts
gas flow as long as the system is powered. The servo pres-
sure regulators monitor outlet pressure to provide an even
main burner gas flow. 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 with-
out lockout timers, the trial for ignition continues indefinitely.