LAARS 9600 CB & HWG - Service Manual - Manual (Page 9)

9600 CB & HWG Service Manual
Page 9
1B. Start Up Procedures
1. Make sure that the system is properly filled, com-
pletely purged of air and system valves are open.
2. Open system gas cock(s) and gas control knob on
gas valve (if closed).
3. Set the room thermostat, aquastat or storage tank
aquastat to call for heat.
4. Turn on electrical power to the unit.
5. The green light on the boiler control will light and
the internal circulator and blower will start. After
a 15 second prepurge the igniter will come on for
20 seconds and then the gas valve will open and
ignition will occur (for more details see
“Sequence of Operation”).
Note: Air in new gas lines may prevent ignition.
The boiler control will make a total of three attempts
for ignition before lockout. To reset the control, switch
off the power switch for 10 seconds.
1C. Checkout Procedures
1. Check burner input rate:
Allow burner to operate for at least 5 minutes
before checking the input. On most LP
installations it will be impossible to check the
input, however, checking combustion as in step 2
below will guarantee proper burner operation. To
check the input (where possible) time the gas
meter to determine the time required for 4 cubic
feet of gas to pass through it. No other equipment
supplied by the gas meter should be operating
when the timing is done. Table 1 can be used to
convert the time to input rate.
Due to the effects of altitude and other minor
variances, it is possible that the input rate will
differ slightly from the rating plate value.
2. Check combustion (see Figure 7).
It is important to check the combustion with a
CO2 or O2 tester (Bacharach for example) to
ensure maximum efficiency and reliability. Insert
the tester sample tube through the exhaust
terminal and at least 6" (152mm) into the flue
pipe. The unit must operate for 5 minutes before
taking a sample. Take a sample and determine the
CO2 or O2
CO2 - 8% to 8.5% (natural gas)
O2 - 7% to 6%
CO2 - 9% to 9.8% (propane gas)
If the burner is not operating in this range it
should be adjusted (see Burner Adjustment).
3. Burner Adjustment
The Heatmaker 9600 CB & HWG burner system
is a pre-mixed forced combustion system. Outside
air is drawn through the air orifice (located in the
rubber hose in the air induction system) and
mixed with the gas which is drawn in downstream
of the air orifice. All the air required for complete
combustion comes into the system in this manner.
The gas is metered through the gas orifice located
in the gas orifice union.
Adjusting the burner is limited to changing the
gas orifice to achieve proper combustion. The air
orifice cannot be altered and the gas valve
pressure should not be changed.
Before changing the gas orifice to adjust the
burner, make the following checks:
a.
Gas valve supply pressure is between 4 and
14 in. W.C. (2.3 and 8.1 oz / in²)
b. The differential pressure on the outlet side
of the gas valve (manifold pressure) is
between -0.05 and -0.35 in. W.C.
If a. and b. are correct proceed as follows:
When measuring CO2 (natural gas units),
readings below 8% generally indicate lean mixture (not
enough gas). Reading above 9 1/4% indicate a rich
mixture (too much gas). Readings for LP units are
higher; below 9 1/4% is lean and above 10 3/4% is
rich. If the readings are below the minimum values,
install a larger gas orifice. If the readings are above the
maximum value install a smaller orifice.
Figure 7. Checking Combustion.
Table 1. Time-to-Input Rate Conversion.
Time (4CF) Input Rate (Natural Gas)
57 sec 252,600 BTU/hr
58 248,300
59 244,000
70 205,700
71 202,800
72 200,000
74 194,600
80 180,000
82 175,600
84 171,400
94 153,200
96 150,000
98 146,900
EXHAUST
TERMINAL
COMBUSTION
TESTER
SAMPLE
TUBE
1/4 IN. PER FT.
9600 CB