Start-Up Procedure; Main Burner Adjustment; Primary Air Shutter(Propane Only); Control Operating Sequence - Modine Manufacturing IPT Installation And Service Manual

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" W.C. for natural gas
and 10" W.C. 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 tab 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 replace
the 1/8" pipe plug.
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
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 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.
9-511
Air
Shutter
Gas Orifice
19