Checking input rate – Modine Manufacturing 6-558.6 User Manual
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Pilot Flame Adjustment
The pilot is orificed to burn properly with an inlet pressure of 6-
7" W.C. on natural gas and 11-14" W.C. on propane gas, but
final adjustment must be made after installation. Adjust to have
a soft steady flame 3/4" to 1" long and encompassing 3/8"-1/2"
of the tip of the thermocouple or flame sensing rod. Normally
this flame will produce satisfactory results. To adjust the flame
use pilot adjustment screw on combination gas control (for
location, see the combination gas control literature supplied
with unit). If the pilot flame is longer and larger than shown by
Figure 7, it is possible that it may cause soot and/or impinge on
the heat exchanger causing burnout. If the pilot flame is shorter
than shown it may cause poor ignition and result in the controls
not opening the combination gas control. A short flame can be
caused by a dirty pilot orifice. Pilot flame conditions should be
observed periodically to assure trouble-free operation.
Natural Gas Flame Control
Control of burner flames on units utilizing natural gas is
achieved by moving the gas manifold to either increase or
decrease primary combustion air. Prior to flame adjustment,
operate unit with casing closed for about five minutes.
Operation can be viewed through the sight glass on the rear of
the unit (see Figure 11a).
Lack of primary air will cause soft yellow-tipped flames. Excess
primary air produces whort, well-defined flames with a
tendency to lift off the burner ports. Proper operation with
natural gas provides a soft blue flame with a well-defined inner
cone.
To increase primary air, remove the access panel (see Figure
11a and 11b). Next loosen the fastening screws holding the
hinged bottom pan in place and lower the bottom pan (see
Figure 14). With the bottom pan lowered, loosen the manifold
mounting screws (see Figure 14) and tap the manifold away
from the mixer tubes until the yellow flames disappear. To
decrease the primary air, move the manifold closer to the mixer
tubes until flames no longer lift from burner ports, but being
careful not to cause yellow tipping. Retighten manifold mounting
screws after adjustment.
Once adjustment has been made all around the bottom pan.
Replace the access panel, again checking for a good tight seal
around the entire perimeter of the access panel. Observe the
burner flame through the sight glass to make sure proper flame
adjustment has been achieved.
Propane Gas Flame Control
Adjustable primary air shutters are attached to the orifices on
the gas manifold for units equipped for propane gas operation
(see Figure 15). An optimum flame will show a slight yellow tip.
Prior to flame adjustment, operate unit heater with casing
closed for at least five minutes. If flame adjustment is
necessary, remove the access panel (see Figure 11a and 11b)
and adjust primary air shutters. Loosen wing screws and push
shutters forward to reduce primary air until yellow flame tips
appear. Then increase primary air until yellow tips diminish to
just a slight yellow tip and an clean blue flame with a well-
defined inner cone appears.
It may also be necessary to adjust the manifold position in
addition to adjusting air shutters to obtain the proper flame.
Follow the instructions under “Natural Gas Flame Control” for
adjusting the manifold.
Replace the access panel making suer a good tight seal is
achieved around the entire perimeter of the access panel.
Observe the burner flame through the sight glass to make sure
proper flame adjustment has been achieved.
CHECKING INPUT RATE
Input Adjustments
The gas pressure regulator (part of the combination gas
control) is adjusted at the factory for average gas conditions. It
is important that gas be supplied to the heater in accordance
with the input rating stamped on the serial plate. Actual input
rating stamped on the serial plate. Actual input should be
checked and necessary adjustments made after the hater is
installed. Over-firing, a result of too high an input, reduces the
life of the unit, and increases maintenance. Under no
circumstances should the input exceed that shown on the rating
plate.
(A) Meter Timing Method
1.
Shut off all other gas-burning equipment, including other
pilot lights served by the gas meter.
2.
Start the heater and determine the number of seconds it
takes to consume 1 cu. ft. of gas. Two basic formulas are
useful:
F1 = 3600 C/T
F2 = F1/C
Where
F1 = input to heater, Btuh.
F2 = input to heater, cu. ft. per hr.
C = heating value of gas, Btu per cu. ft.
T = time to consume 1 cu. ft. of gas in sec.
The heating value of gas may be determined from the local
utility or gas dealer.
These are representative values:
GAS
Btu per cu. ft.
Natural
1000-1150
Propane
2500
3.
If the seconds for 1 cu. ft. are more (input less) than shown
in Table 5 for model being tested, remove the access panel
(see Figure 11a). With access panel removed, locate the
combination gas control and pressure regulator adjustment
screw (see Figure 11b). Remove the cap screw from he
pressure regulator and take one clockwise turn at a time on
the adjustment screw until the correct time is obtained. If
the seconds are less (input greater)than indicated in the
table, follow the same procedure in a counter-clockwise
direction.
If the correct number of seconds cannot be obtained check
orifice size. Correct orifices can be obtained from Modine
Manufacturing Company, Racine, Wisconsin. When requesting
orifices, state type of gas, heating value, and its specific gravity.
Also give model number of unit.
For example, if the input to the heater is 100,000 Btuh and the
heating value of the gas is 1000 Btu per cu. ft., then, by the
second formula, the input is 100 cu. ft. per hr. Table 4 indicates
the time for one revolution of various size meter dials with
various input rates. If a 1 cu. ft. meter dial is used, we proceed
down the cu. ft. column to 100 cu. ft. per hr. and then
horizontally to the left to determine a time of 36 seconds for
one revolution of the dial. Similarly, if the 1/2 cu. ft. dial is used,
we determine a time of 18 seconds for one revolution at the
required input.
After proper firing rate has been achieved, replace regulator
cap crew and replace access panel, making sure a good tight
seal is achieved around the entire perimeter of the access
panel.