32
Press the “
” button on the control screen.
Press
[Test]
and press
Select [Forced Rate] and Press
Select
[Set Low Fire]
Once the water heater has run for at least 10-15 minutes at
low fire, with the coldest possible water, the condensate in
the lower heat exchanger will be at maximum volume. At this
point adjust the combustion for CO
2
.
Turn the gas valve low fire adjustment clockwise to increase
CO
2,
and counter-clockwise to decrease CO
2
.
Increase CO
2
Decrease CO
2
Low Fire
Adjustment
Clockwise
Counter-Clockwise
After adjusting the setting, wait for the combustion levels to
stabilize before attempting to make any further adjustments.
Continue this procedure until combustion levels are satisfied.
Once settings are complete, continue to run the machine for
at least 5 minutes and record the final combustion data.
8.3.2
– Adjust High Fire Setting
VT80 to 250
– Negative Pressure Control Valve
VT299 to VT399
– Negative Pressure Control Valve
VT499
– Negative Pressure Control Valve
Ensure low fire adjustment is completed first.
Press the “
” button on the control screen.
Press
[Test]
and press
Select [Forced Rate] and Press
Select
[Set High Fire]
Bring the temperatures up to 130F or the highest system
design temperatures to minimize or eliminate condensate
Turn the gas valve low fire adjustment counter-clockwise to
increase CO
2
, and clockwise to decrease CO
2
.
Increase CO
2
Decrease CO
2
High Fire
Adjustment
t
Counter-Clockwise
Clockwise
After adjusting the screw wait a moment for the combustion
levels to stabilize before attempting to make any further
adjustments.
Continue this procedure until combustion levels are satisfied.
Once settings are complete, continue to run the machine for
at least 5 minutes and record the final combustion data.
8.3.3
– Flame Monitoring
Throughout the combustion setup process, it is important to
visually check flame to verify combustion settings.
WARNING
The area around the burner view port is hot and direct
contact could result in burns
Normal Burner Flame Profile
(Short, Dense and Blue)
Normal Flame
–
A normal flame at 100% of burner input is
blue, with slight yellow tips a well-defined flame and no flame
lifting.
Yellow Tip
–
A yellow tip can be caused by blockage or
partial obstruction of air flow to the burner.
Yellow Flames
–
A yellow flame can be caused by blockage
of primary air flow to the burner or excessive gas input. This
condition
MUST
be corrected immediately
Lifting Flames
–
Lifting flames can be caused by over firing
the burner, excessive primary air, or excessive draft.
If improper flame is observed, examine the venting system;
ensure proper gas supply and adequate supply of combustion
and ventilation air.
8.4
– Final Commissioning
Check appliance performance by cycling the unit repeatedly.
The burner should ignite promptly each time. Turn system off
and allow burner to cool, then cycle burner again to ensure
proper ignition and flame characteristics.
The unit must continue to run with stable combustion without
making any howling noise which usually happens from an
overly rich mixture.
High-fire air gas ratio
adjustment (Use slotted
screwdriver for
adjustment, counter-
clockwise increases CO
2
)
Lift top cover to access high fire air/gas
ratio adjustment (use 3mm Allen key
for adjustment, counter-clockwise
increases CO
2)
High-fire adjustment screw (use slotted
screwdriver for adjustment, counter-
clockwise increases CO
2
)
