Modine Manufacturing PV Installation And Service Manual page 12

C C H H E E C C K K I I N N G G I I N N P P U U T T R R A A T T E E
I I n n p p u u t t A A d d j j u u s s t t m m e e n n t t s s
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 should
be checked and necessary adjustments made after the heater 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.
Input can be determined by the meter-timing method provided
other gas equipment connected to the meter is off during the
test. If this is not possible, use the pressure method.
( ( A A ) ) M M e e t t e e r r T T i i m m i i n n g g M M e e t t h h o o d d
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
Natural
Propane
3. If the seconds for 1 cu. ft. are more (input less) than shown in
Table 5 for model being tested, locate the combination gas
control and pressure regulator adjustment screw (see Figure
11b). Remove the cap screw from the 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 c c o o u u n n t t e e r r - - c c l l o o c c k k w w i i s s e e direction.
If the correct number of seconds cannot be obtained check
orifice size. Correct orifices can be obtained from Modine
Manufacturing Company, Buena Vista, Virginia. 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 5 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 screw.
1 1 2 2
Btu per cu. ft.
1000-1150
2500
T T a a b b l l e e 5 5
M M e e t t e e r r - - t t i i m m i i n n g g G G a a s s
(Time required for one revolution is charted for various size
meter dials and various rates of gas input in cu. ft. per hour. To
convert to Btuh, multiply by the heating value of the gas used.)
T T i i m m e e f f o o r r 1 1 I I n n p p u u t t , , C C u u . . F F t t . . p p e e r r H H o o u u r r , , w w h h e e n n m m e e t t e e r r d d i i a a l l s s i i z z e e i i s s : :
R R e e v v o o l l u u t t i i o o n n , ,
S S e e c c . . 1 1 / / 2 2 c c u u . . f f t t . .
10 180
12 150
14 129
16 112
18 100
20 90
22 82
24 75
26 69
28 64
30 60
35 51
40 45
45 40
50 36
55 33
60 30
70 26
80 22
90 20
100 18
120 15
F F i i g g u u r r e e 9 9
D D i i a a l l s s o o f f T T y y p p i i c c a a l l G G a a s s M M e e t t e e r r
( ( B B ) ) P P r r e e s s s s u u r r e e M M e e t t h h o o d d
The pressure method determines input by measuring the
pressure of the gas in the manifold in inches of water.
1. Determine correct manifold pressure from Table 5a.
2. Locate combination gas control.
3. Move gas control knob (or lever) to OFF.
4. Remove the 1/8" pipe plug in outlet pressure tap in
combination gas control (see Figure 11b) and attach water
manometer or "U" tube which is at least 12" high.
5. Follow lighting instructions and turn thermostat up to get
unit to fire.
6. If pressure as indicated by "U" tube is less than 1/2" higher
or lower than indicated in Table 5a, adjust regulator as
described under "Meter-Timing Method," Step 3.
If pressure as indicated by "U" tube is more than 1/2" higher
or lower than indicated in Table 5a, check inlet pressure at
unit. The inlet pressure should be 6-7" W.C. pressure on
natural gas and 12-14" W.C. on propane gas.
After adjustment, move gas control knob (or lever) to OFF and
replace 1/8" pipe plug. With plug in place follow the lighting
instructions to put unit back in service.
1 1 c c u u . . f f t t . . 2 2 c c u u . . f f t t . . 5 5 c c u u . . f f t t . .
360 720 1800
300 600 1500
257 514 1286
225 450 1125
200 400 1000
180 360 900
164 327 818
150 300 750
138 277 692
129 257 643
120 240 600
103 206 514
90 180 450
80 160 400
72 144 360
65 131 327
60 120 300
51 103 257
45 90 225
40 80 200
36 72 180
30 60 150