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POWER
VT®WATER
HEATER
GAS BURNER START-UP
(Refer to Figure 19-6, page 11 to identify burner parts)
WARNING:
START~UP
SHOULD ONLY BE PERFORMED BY A QUALIFIED TECHNICIAN.
1. Remove enclosure panel cover on .thE; water
heater to expose control circuit. A wiring dLsgram,
included in this packet, will show the :.ontrols
used in our circuitry.
2. Visually check that all components are
int~"\ct
and
no damage has occurred during transit
3. Check all connections within the control cabinet.
A loose connection could cause intermittent
shutdowns.
4. Some burners will use direct spark ignition They
may use a single gas pressure regulator and gas
valve or multiple valves and regulators. 01'
a
call
for heat, the motor starts, gas primary. control is
energized, the air vent damper opens and after a
short delay (pre-purge), the gas valve(s) opens
and ignition should occur.
NOTE: Do not tamper with or readjust program
dipswitch settings. This will cause the control to
become inoperable. Damage resulting from
tampering
will be excluded from coverag( under
the warranty of this unit.
5. Connect
a
test meter to the control for
p~ading
the flame response signal.
NOTE: Some controls read the flame
si~lflal
in
micro amps and some in volts DC. The M series
control has two terminals marked for reading
volts in DC.
CAUTION: Be sure the tank is filled with
water. Dry firing can destroy the water
heater.
6. Check the gas pressure before start-up, u$ing a
U-tube manometer or a 0 to 28" W.C. pre.ssure
gauge for inlet gas pressure. (This is the
pressure measured before all components in the
gas train.) The manometer must stay connected
throughout the testing, as the inlet pressure must
be monitored. during the firing of the burner.
Record static pressure; it must not exceed 14"
W.C. Pressures above this could cause damage
to the diaphragm in the gas valve or pr€:ssure
regUlator.
7. Connect a manometer to the manifold test port at
the shutoff valve closest to the burner.
Tl.lrn
off
main gas shutoff valve. Turn unit on using the
rocker switch on the side of the control enclosure
assembly. If the operating control switches are
closed, the burner blower should come on and
pre-purge begins.
8. If nothing happens, check the control; if it is not in
the tripped position, reset it by pushing the flame
safeguard reset button. The burner should pre-
purge at least thirty seconds.
9. When the blower motor starts, the air damper will
open and the airflow prOVing light or; the
MEC120 should be on. This indicates a positive
airflow condition. If the air proving light is not on,
check the air-proving switch for operation. To
adjust the air-proving switch, turn the adjustment
screw counter-clockwise until the air proving light
comes on, then turn the screw one turn counter-
clockwise. If the gas valves open and close
intermittently during normal operation, turn screw
one
half turn
counter-clockwise
until
this
condition ceases. This procedure should be
followed with every burner.
This section is for single-stage and two-stage
firing: After purging is complete, terminal 3 on
the flame control energizes the pilot valve and
terminal 4 energizes the ignition transformer. The
pilot is then established. The VDC reading on the
meter should read
a
steady 6-10 VDC; 6 VDC is
{he minimum flame signal for it to operate
reliably. If the pilot fails to light during the initial
period, it is probably due to air in the line. The
control will lock out and require reset.
Once the flame is established, the ignition
transformer will de-energize and terminal 5 will
energize the main valve. At this point the water
heater is operating at maximum firing rate (high
fire). In order to insure the water heater is
operating at the rated input, it is necessary to
check the manifold gas pressure (measured at
the pressure tap on the gas valve closest to
burner). The manifold gas pressure should be
adjusted at main gas regulator to the factory
recommended
pressure
shown
on
tag
attached to gas train. Do not screw the
adjusting nut of the regUlator in beyond point
where no further Increase in manifold pressure
is noted.
PV500-19 04-2005
12
Section 19
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