Modine MDB Série Manuel D'installation Et De Maintenance page 20

start-uP Procedure
Figure 20.1 - Profile Pressure Pickup tube reference
views
PS-10 - LOW
AIRFLOW SWITCH
(NORMALLY OPEN)
HIGH
LOW
CLAMP
CONNECTORS
AIRFLOW
SENSING TUBING
BURNER PROFILE
SIDE PANEL
PS-10 - LOW
AIRFLOW SWITCH
(NORMALLY OPEN)
HIGH
LOW
CLAMP
CONNECTORS
AIRFLOW
SENSING TUBING
BURNER PROFILE
SIDE PANEL
PS-10 - LOW
AIRFLOW SWITCH
(NORMALLY OPEN)
HIGH
LOW
CLAMP
CONNECTORS
AIRFLOW
SENSING TUBING
BURNER PROFILE
SIDE PANEL
PS-10 - LOW
AIRFLOW SWITCH
(NORMALLY OPEN)
HIGH
LOW
CLAMP
CONNECTORS
AIRFLOW
SENSING TUBING
COMPARTMENT
COMPARTMENT
TO PICKUP TUBE
AFTER BURNER
TO PICKUP TUBE
BEFORE BURNER
20
PS-11 - HIGH AIRFLOW
CUTOFF SWITCH
(NORMALLY CLOSED)
HIGH
LOW
TEE
CONNECTORS
PIPING
COMPARTMENT
BURNER
COMPARTMENT
AIRFLOW
DIRECTION
PS-11 - HIGH AIRFLOW
CUTOFF SWITCH
(NORMALLY CLOSED)
HIGH
LOW
TEE
CONNECTORS
PIPING
COMPARTMENT
BURNER
COMPARTMENT
AIRFLOW
DIRECTION
PS-11 - HIGH AIRFLOW
CUTOFF SWITCH
(NORMALLY CLOSED)
HIGH
LOW
PIPING
COMPARTMENT
BURNER
COMPARTMENT
BURNER PROFILE
SIDE PANEL
(OPPOSITE SIDE)
AIRFLOW
DIRECTION
PS-11 - HIGH AIRFLOW
CUTOFF SWITCH
(NORMALLY CLOSED)
HIGH
LOW
PIPING
BURNER
AIRFLOW
DIRECTION
start-up Procedure (continued)
f. If the required differential cannot be achieved, the
blower speed may have to be adjusted. Refer to page
25 for blower adjustments.
For example, if the required burner velocity pressure
differential should be between 0.45"W.C. and 0.55"W.C.
and the actual reading is less than 0.45", the blower speed
will have to be increased. If the actual reading is greater
than 0.55" the blower speed will have to be reduced.
Note: Whenever the blower speed is changed, the
motor amp draw must be rechecked to assure that the
motor does not become overloaded.
If the required differential cannot be achieved through
blower speed adjustments, refer to the section, "Adjusting
Burner Profile Pressure Differential" on page 22.
g. When the correct burner velocity pressure differential
is achieved, turn the unit off and open the main
disconnect switch. Remove replace the tubing
removed in Step (a) and the low airflow pressure
switch jumper that was added in Step(b).
Steps 27-33 must be performed on HIGH SPEED if unit is
equipped with a VFD.
27. The high fire manifold pressure (at the burner) must be
checked to ensure it matches the pressure shown on the
unit serial plate. Over-firing from high pressure can result
in poor combustion and undesirable levels of products of
combustion being introduced into the heated space. The
procedure is outlined in the following steps.
28. With the unit off, close the main gas manual hand valve.
Remove the 1/8" pipe plug test port at the burner and
attach a water manometer or "U" tube that is at least
12" high. See piping diagram furnished with the unit for
pressure tap locations.
29. Open the main gas manual hand valve and start the unit.
Observe the flame at low fire start to make sure it lights
across the entire length of the burner and is stable with a
clean blue flame.
30. Adjust the temperature control setting to force the unit to
high fire. Observe the pressure indicated on the "U" tube
manometer:
• If the pressure is not more than 1/2" higher or lower
than indicated on the unit serial plate, adjust the gas
valve regulator until the pressure matches the setting
on the unit serial plate.
• If the pressure is more than 1/2" higher or lower
than indicated on the unit serial plate, check the inlet
gas pressure to the unit. Adjust the main gas supply
regulator to supply the correct gas inlet pressure to the
setting shown on the unit serial plate.
31. With the high fire manifold pressure set to match the
setting on the unit serial plate, observe the flame at high
fire. The flame should be stable and burning clean. A slight
orange tip may be present and is acceptable.
32. Turn the temperature controls down to their lowest setting
and check the low fire burner flame. It should still be stable
and burning clean and 1 to 2 inches long. If necessary,
adjust the low fire gas pressure on Maxitrol valve (VG-07)
so the unit operates correctly as described.
33. Recycle the ignition sequence to make sure the burner
lights off smoothly and the gas lights across the entire
length of the burner.
7-500.10