3
VFC 15-150 / VFC 45-225
NATURAL GAS coNveRSioN PARTS KiT# P-176
120-170 R2
1.
Turn off the boiler’s gas shut off valve. with a small (1/8” or 3 mm) flat
screwdriver, open the inlet gas supply pressure test port by turning its center-
screw 1 full turn counterclockwise. attach a manometer to the pressure
test port and turn on gas to appliance. static manometer reading should be
ideally 7” w.c. for natural Gas. Minimum and maximum static pressure should
be between 3” and 14” w.c. Monitor pressure throughout the comissioning
procedure. Pressure may droop up to 1” to 2” w.c. at high fire. outlet Pressure
(Manifold Pressure) should be between -0.04” w.c. and 0.00” w.c. with a
target of -0.02” w.c.
NOTE:
The outlet pressure should only be measured
with an accurate digital manometer. Consult factory before considering field
adjustment.
2.
Turn the high Fire (Gas:air ratio) screw one turn anti-clockwise (riching
direction) using a small flat screwdriver.
3.
set a load as Manual Control and run the boiler at the maximum firing rate
(150 or 225 MBh as applicable). This load should be large enough to allow the
boiler to operate at high fire for 20 plus minutes. Take note of what the load
was set for before you change it to Manual Control.
4.
do not insert your analyzer yet – wait until after step# 6.
5.
at full-fire, the flame should be a blue-orange mix. If the flame is bright orange
further adjust (clockwise) the high Fire (Gas:air) ratio screw until you obtain a
blue-orange flame.
6.
with a combustion analyzer probe in the flue gas test port, turn the high Fire
(Gas : air ratio adjustment) screw clockwise
(see diagrams on this page)
to achieve results. This screw offers very fine adjustment, and may require
several turns.
NOTE:
Clock the gas meter to confirm full maximum rating plate
input. Check the measured results with Table 3 - high Fire.
There is often backlash when you adjust the (Gas:air) ratio screw, so small
adjustments (e.g. 1/4 turn or less per movement,) should be made, with
sufficient time between adjustments for the analyzer to read the adjustments.
7.
In the Manual Control mode adjust the firing rate to low Fire (15 / 45 MBh
as appropriate). adjust the low Fire (Zero-offset) adjustment screw until your
analyzer readings are within the range shown in Table 2.
NOTE:
This adjustment is very sensitive, only small movements, e.g. 1/4 turn
per adjustment, reducing to much smaller steps as the target is approached as
applicable. wait 2-3 mins before making another adjustment.
NOTE:
The effect of the low Fire screw is reversed: Clockwise richens the
mixture and counter clockwise leans the mixture.
8.
reset the boiler to high Fire and recheck the analyzer readings with Table 2.
9.
reset the boiler to low Fire and recheck the analyzer readings with Table 2.
10.
Turn Manual Control off by setting the load to its previous setting and remover
the jumper. all the programmed settings will be restored and the load will
operate as it did previously. Turn off the gas supply, remove the manometer
and close the gas pressure test port.
11.
restore gas supply by opening the gas control valve, and using an approved
leak detection solution, soap test all joints.
clocking the Meter
(Natural Gas)
1.
Turn off all other appliances and
pilots
2.
Turn on the boiler and set the
boiler to high fire. ensure the
boiler has a large load to heat so
that the boiler will not shut off.
3.
with a stop-watch, record
the number of seconds for the
smallest dial to make 1 full
revolution.
4.
CFh = (3600 x dial size) /
seconds
5.
CFh x 1000 (check local Btu
content) = Input Btu’s
NOTE:
•
For 2 PsI meters multiply CFh x
1.097
•
For Metric meters multiply CFh x
35.3
•
For 2 PsI metric meters multiply
CFh x 1.097 x 35.3
•
For altitude above 4,500’ deduct
2% per 1,000' of altitude from the
Input Btu’s
Zero-offset adjustment screw
Gas:Air ratio adjustment screw
