Modine Manufacturing PDP Installation And Service Manual page 11

start-uP Procedure
to adjust the manifold Pressure
1. Move the field installed manual shut-off valve to the "OFF"
position.
2. Remove the 1/8" pipe plug in the pipe tee or gas valve and
attach a water manometer of "U" tube type which is at least
12" high.
3. Move the field installed manual gas shut-off valve to the "ON"
position.
4. Create a high fire call for heat from the thermostat.
5. Determine the correct high fire manifold pressure. For natural
gas 3.5" W.C., for propane gas 10" W.C. Adjust the main
gas pressure regulator spring to achieve the proper manifold
pressure (for location, see the combination gas control
literature supplied with unit).
6. After adjustment, move the field installed manual shut-off
valve to the "OFF" position 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 soap solution.
Burner flame adjustment
Proper operation provides a soft blue flame with a well-defined
inner core. A lack of primary air will reveal soft yellow-tipped
flames. Excess primary air produces short, well-defined
flames with a tendency to lift off the burner ports. For both
natural and propane gas, the flame may be adjusted by sliding
the manifold. Also, for propane gas, the air shutters can be
adjusted to control the burner flame height. The air shutters
can be accessed by lowering the bottom pan of the unit heater.
natural Gas flame control
Control of burner flames on unit heaters utilizing natural gas is
achieved by resetting the manifold position to either increase
or decrease primary combustion air. Prior to flame adjustment,
operate unit heater for about fifteen minutes. The main burner
flame can be viewed after loosening and pushing aside the gas
designation disc on the back of the unit.
To increase primary air, loosen the manifold mounting screws
and move the manifold away from the burner until the yellow-
tipped flames disappear (see Figure 11.2). To decrease primary
air, move manifold closer to the burner until flames no longer lift
from burner ports, but being careful not to cause yellow tipping.
Retighten manifold mounting screws after adjustment.
Propane Gas flame control
An optimum flame will show a slight yellow tip. Prior to flame
adjustment, operate furnace for at least fifteen minutes. Loosen
air shutter set screws and move the air shutters away from the
manifold to reduce the primary air until the yellow flame tips
figure 11.1 - typical combination Gas control
GAS CONTROL kNOB
PRESSURE REGULATOR
ADJUSTMENT SCREW
(UNDER CAP SCREW)
INLET
PRESSURE
TAP
INLET
RESET BUTTON
OUTLET
PRESSURE
TAP
OUTLET
PILOT TUBING
CONNECTION
PILOT ADJUSTMENT
SCREW
appear (see Figure 11.3). Then increase the primary air until
yellow tips diminish and a 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 proper flame. Follow
the instructions under "Natural Gas Flame Control" for adjusting
the manifold.
table 11.1 - manifold Pressure & Gas consumption ➀
Btu/cu. ft.
model specific Gravity
manifold Pressure in. W.c.
CFH
PDP 150
Gal/Hr. Propane
BDP 150
Orifice Drill Size
CFH
PDP 175
Gal/Hr. Propane
BDP 175
Orifice Drill Size
CFH
PDP 200
Gal/Hr. Propane
BDP 200
Orifice Drill Size
CFH
PDP 250
Gal/Hr. Propane
BDP 250
Orifice Drill Size
CFH
PDP 300
Gal/Hr. Propane
BDP 300
Orifice Drill Size
CFH
PDP 350
Gal/Hr. Propane
BDP 350
Orifice Drill Size
CFH
PDP 400 Gal/Hr. Propane
Orifice Drill Size
➀ Above gases based on average standards. (Gal./Hr. based on
60°F. 30" Hg., 91,500 BTU/Gal.) In Canada, refer to rating plate on
side of unit for orifices at high altitude.
figure 11. - manifold adjustment, natural Gas
MANIFOLD
MIXER
TUBES
BURNER
RETAINING PIN
figure 11.3 - air shutter adjustment, Propane Gas
MANIFOLD
6-580.4
natural Propane
1050 500 no. of
0.60 1.53 orifices
3.5 10.0
138.1 58.0
– 1.64 2
21 39
166.7 70.0
– 1.86 3
28 43
190.5 80.0
– 2.19 3
25 42
238.1 100.0
– 2.74 3
18 36
285.7 120.0
– 3.29 4
21 39
333.3 140.0
– 3.84 5
23 41
381.0 160.0
– 4.38 6
25 42
MAIN
BURNER
ORIFICES
MANIFOLD MOUNTING
SCREW AND PIN
MAIN
BURNER
AIR
ORIFICES
SHUTTER
MIXER
TUBES
11