Blodgett MT2136 Series, Service And Repair Manual

Page: 34 / 94

OPERATION
3-10
temperature passing its face exceeds the ratĆ
ing on the back of the switch.
NOTE: The switch is located between two conĆ
vection blowers in the rear convection
fan compartment. It protects the other
components from hi ambient heat.
If this switch is cold it should be closed sending
power to the common terminal of a differential
pressure switch (16). The pressure switch is
made between common and N.C. when the
combustion motor (10) is idle. When the comĆ
bustion motor reaches full speed the differenĆ
tial pressure switch toggles from common and
N.C. to common and N.O. sending power to
the single solenoid gas valve (17).
NOTE: The differential pressure switch
toggles due to a change in air pressure
created by the combustion motor.
4. There are two cooling fans (18) located in the
rear convection fan compartment. These fans
are activated when the N.O. SPST thermal
switch (19) closes due to high ambient heat.
The switch toggles if the temperature passing
its face exceeds the rating on the back of the
switch.
NOTE: The switch is located between the two
blowers in the rear convection fan
compartment. It protects the convecĆ
tion fans from hi ambient heat.
A third cooling fan (18) is located in the control
box compartment. This fan is activated when
another N.O. SPST thermal switch (20) closes.
The switch toggles if the temperature passing
its face exceeds the rating on the back of the
switch.
NOTE: The switch is located in the slide out
control compartment. It protects the
controls from hi ambient heat.
5. The conveyor is driven by an open loop D.C.
control system consisting of a conveyor switch
(21), time display (22), 10k W potentiometer
(23), D.C. speed control board (24), 180 VDC
motor (25) and #10 Hall effect pickup (26). AfĆ
ter the conveyor switch is turned on, the time
display illuminates. The D.C. control board
powers up. The output voltage measured on
terminals A1 and A2 of the board to the motor
varies from 20 to180 VDC based on the posiĆ
tion of the potentiometer. The speed of the moĆ
tor should also vary. The time display varies deĆ
pending on the speed of the Hall effect pickup.
The pickup sends an R.P.M. value to the disĆ
play. The display converts this value to minĆ
utes:seconds.
NOTE: This type of system does not sense the
weight of the product and will slow
down slightly if the belt is fully loaded.