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START-UP PROCEDURE
Main Burner Adjustment
The gas pressure regulator (integral to 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 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 serial plate.
Measuring the manifold pressure is done at the manifold
pressure tap on the main gas valve on the heater.
To adjust the manifold pressure:
1. The correct manifold pressure is 3.5" high fire and 2.5" W.C.
low fire for natural gas.10" high fire and 6.2" W.C. low fire for
propane gas. Adjust the main gas pressure regulator spring to
achieve the proper manifold pressure.
2. Move the field installed manual shut-off valve to the "OFF"
position.
3. Remove the 1/8" pipe plug in manifold pressure tap or use the
pressure tap tower in the combination gas control and attach
a water manometer of "U" tube type that is at least 12" high.
Instructions for units with the pressure tap towers:
The inlet (IN P) and outlet (OUT P) pressure ports accept a 5/16"
ID hose connection. Using a 3/32 (2.3mm) inch hex wrench,
rotate pressure tap screw one revolution counter-clockwise (when
measuring pressure, only loosen but do not remove screw).
4. Move the field installed manual shut-off valve to the "ON"
position.
5. Create a call for heat from the thermostat.
6. After adjustment, move the field installed manual shut-off
valve to the "OFF" position, remove manometer and hose
from the outlet boss. turn outlet pressure tap screw clockwise
to seal the pressure port. Tighten to 13 in. -lbs. minimum.
7. After the plug is in place, move the field installed manual shut-
off valve to the "ON" position and recheck pipe plugs for gas
leaks with a soap solution.
8. Replace the side access panels.
Table 19.1 - Manifold Pressure and Gas Consumption
Type of Gas
3
Input MBH
Btu/ft
Specific Gravity
Manifold Pressure " W.C.
CFH
50
Gal/Hr.Propane
Orifice Drill Size
CFH
60
Gal/Hr.Propane
Orifice Drill Size
CFH
75
Gal/Hr.Propane
Orifice Drill Size
CFH
100
Gal/Hr.Propane
Orifice Drill Size
CFH
125
Gal/Hr.Propane
Orifice Drill Size
CFH
150
Gal/Hr.Propane
Orifice Drill Size
CFH
175
Gal/Hr.Propane
Orifice Drill Size
CFH
200
Gal/Hr.Propane
Orifice Drill Size
Natural
Propane
No. of
1040
2500
Orifices
0.6
1.53
3.5
10
48.1
20.0
n/a
0.55
1
3.3 mm
2.0 mm
57.7
24.0
n/a
0.66
1
#27
#43
72.1
30.0
n/a
0.83
1
#22
#38
96.2
40.0
n/a
1.10
1
#11
#32
120.2
50.0
n/a
1.38
1
#3
#30
144.2
60.0
n/a
1.65
1
#B
#28
168.3
70.0
n/a
1.93
1
#F
#23
192.3
80.0
n/a
2.20
1
#L
#18
9-511.4
Primary Air Shutter (Propane Gas Only)
Propane gas models 75-200 are equipped with an adjustable
primary air shutter, mounted flush with the end of the gas
orifice, as shown in Figure 19.2. These are set at the factory;
do not adjust.
Figure 19.2 - Propane Gas Primary Air Shutter on
75-200 Models Only
Control Operating Sequence
These models utilize a combination gas valve/ignition controller
and a single or two stage thermostat.
1. The thermostat calls for heat.
2. The combustion air blower is energized and begins a fifteen
(15) second pre-purge cycle. The pre-purge clears any
residual gas left over from the previous operation.
3. The pressure switch closes during the pre-purge, energizing
the indicator light on the back of the burner box.
4. The ignition control board is energized and the spark igniter
attempts to light the gas at the burner. Ignition trial time is 7
seconds.
5. Upon proper ignition, the flame is visible through the
combustion chamber sight glass (see Figure 22.2). The unit
continues to operate until the thermostat is satisfied,
at which time the thermostat contacts open and the gas valve
is de-energized until the thermostat makes another call for
heat.
6. If a flame is not sensed for any reason, the main gas valve
will close and there will be a short purge period before ignition
is tried again.
7. If flame is not sensed after three re-tries (four total tries), there
will be at least a one hour wait before ignition is tried again.
Power can be interrupted during this one-hour lockout to reset
the sequence of operation.
8. On single stage units, the main gas valve is opened and the
main burner is lit to 100% full fire.
9. 2-stage High heat warm-up. The control will run in high fire for
the first 30 seconds following flame recognition period
regardless of W2 demand. If W2 is not energized, or is in auto
staging condition, at the end of this 30 second period the
control de-energizes the high gas output (low gas remains
energized). If W2 is energized the control remains on high
heat.
10. 2-stage Low heat operation, the control keeps the main gas
valve and induced draft motor energized while monitoring the
call for heat. .
11. 2-stage High heat opearation. If the P5 shunt jumper is in
place, the control will automatically stage into second stage
following 10 minutes of a steady call for heat.
Air
Shutter
Gas Orifice
19
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