Modine MDB Série Manuel D'installation Et De Maintenance page 19

start-uP Procedure
start-up Procedure (continued)
23. Check for proper signal output for the pilot safety control.
The unit has been supplied with a flame rod sensor.
The output signal from the sensor should be stable and
in accordance with the flame safeguard manufacturer's
recommended signal strength.
For units with a Honeywell flame safeguard control the
signal should be between 3-5 Vdc (Min. of 1.25 Vdc, Max.
of 5 Vdc).
Adjust the pilot regulator and/or pilot line orificed needle
valve up or down if the pilot signal reading is outside of the
manufacturer's specified range.
24. Check to make sure the flame sensor and flame safeguard
relay is operating correctly.
To check, shut off the pilot gas hand valve while the pilot
is still lit. The pilot flame should go out and the pilot ignitor
should try for re-ignition within 2 to 4 seconds. Because
the pilot gas is off, and the pilot cannot be re-established,
the flame safeguard control should go into lockout. (If
the flame safeguard control does not go into lockout, see
separate vendor literature shipped with the unit for trouble
shooting and corrections.)
25. Turn the pilot gas hand valve to the on position and reset
the flame safeguard relay using the flame safeguard
manual reset button. Allow the unit to re-establish the pilot.
26. The burner profile velocity pressure differential must be
checked after installation, with all accessories and
ductwork installed, to assure correct air velocity across the
burner. Check the pressure differential across the profile
plate using an inclined manometer per the following:
a. Review Table 19.1 to determine which Reference View
(Figure 20.1) applies to the unit.
• For Views 1, 2, and 4, remove the factory installed
plastic tubing that runs between the aluminum pickup
tubes and the tee that splits the tubing to both the
low airflow proving switch (PS-10) and the high
airflow cutoff switch (PS-11). The tubing should be
removed from the aluminum air pressure differential
pick-up tubes. Slide the inclined manometer tubes
over the ends of the aluminum pickup tubes.
• For View 3, remove the factory installed plastic tubing
that runs between the aluminum pickup tubes
and the high airflow cutoff switch (PS-11). The
tubing should be removed from the aluminum air
pressure differential pick-up tubes. Slide the inclined
manometer tubes over the ends of the aluminum
pickup tubes.
b. The low airflow proving switch (PS-10) must be
jumped out of the circuit during this test. To jumper
the switch, place a jumper wire on the unit terminal
strip to which the switch is wired. For units with 24V
flame safeguard controls, the typical terminals are 21
and 40. For units with 115V flame safeguard controls,
the typical terminals are 105 and 134. For additional
information on identifying the flame safeguard control
voltage and appropriate terminals, see both page 11
of this manual and the job specific wiring diagram
supplied with the unit. Note that the jumper wire must
be removed after completing this test.
c. The test is to be run with the unit operating (blower
running) in the 100% outdoor air mode. For units
equipped with a VFD, the unit must be running at high speed.
d. If the outdoor air temperature is below 60°F, fire the
main burner to achieve a discharge air temperature
of approximately 70°F. If the burner does not fire
under these conditions, refer to the Service and
Troubleshooting Table 42.1, Section E for additional
guidance. If the outdoor temperature is 60°F or greater,
do not fire the main burner.
e. Read the pressure differential reading on the
manometer and compare against the required value
in Table 19.2. Note that the pressure differential
reading is dependent on the elevation above sea level
for which the unit is installed and must be within +/-
0.05"W.C.
For example, for a MRB unit installed at 4500 feet
above sea level, with a 70°F discharge air
temperature, the profile pressure differential should be
0.50"W.C. The actual installed pressure differential
reading must be 0.50"W.C. +/- 0.05"W.C., or
0.45"W.C. to 0.55"W.C.
table 19.1 - Profile Pickup tube Pressure drop
Model Configuration
model
model Gas type digit 17
j
A
B
Natural
thru
H
MDB
A
B
Propane
thru
H
F
MRB Natural thru
N
j Model Digit 17=A represents single speed units.
Model Digit 17=B thru H represents variable frequency drive units (on Model MDB only).
Model Digit 17=F thru N represents return air units (on Model MRB only).
k For correct profile pressure drop values, refer to Table 19.2 for the Pressure
Setting Group determined in the table above.
table 19.2 - Profile Pickup tube Pressure drop (W.c.)
Pressure
setting
2001-
Group l
0-2000
3000
A 0.47
B 0.60
C 1.41
D 1.80
l Refer to Table 19.1 to determine the correct Pressure Setting Group to use.
7-500.10
Figure 20.1
serial
reference
number
drawing
digit 19
1 or <blank> View 1
1 or <blank> View 2
2 View 3
1 or <blank> View 1
1 or <blank> View 2
2 View 3
1 or <blank> View 4
Elevation Above Sea Level (ft)
3001- 4001- 5001-
4000 5000 6000
0.42 0.41 0.39 0.38
0.54 0.52 0.50 0.49
1.27 1.22 1.18 1.13
1.62 1.56 1.50 1.47
Pressure
setting
Group k
A
C
A
B
D
B
B
6001- 7001-
7000 7500
0.36 0.36
0.46 0.46
1.09 1.07
1.38 1.38
19