Controls Descriptions - Modine MDB Série Manuel D'installation Et De Maintenance

control descriPtions
Before continuing with the start-up and checkout procedure, it
is important to familiarize yourself with the controls furnished
with the unit. Review the documents shipped with the unit to
determine which controls are included.
Pages 11 through 16 provide photographs and descriptions
for each control. The typical locations of the electrical and
gas controls are shown on pages 16 through 17. The typical
locations of the blower and motor components are shown on
page 21.
Once a thorough review of these controls and devices has
been made, the step-by-step Start-Up Procedure as described
on pages 18 through 24 must be performed.
standard safety controls and manifold
low air Flow Proving switch (Ps-10)
The low air flow proving switch monitors the pressure drop
across the burner profile plate to insure that sufficient air flow
exists before allowing the burner to operate. The low air flow
proving switch is located in the gas controls cabinet and is
electrically interlocked with the gas controls. See page 17 for
location.
high air Flow cutoff switch (Ps-11)
The high air flow cutoff switch monitors the pressure drop
across the burner profile plate to insure that the air flow
through the burner does not exceed the maximum design
velocity. The high air flow cutoff switch is located in the gas
controls cabinet and is electrically interlocked with the gas
controls. See page 17 for location.
Figure 11.1 - low airflow Proving/high airflow
cutoff switch (only one shown)
high temperature limit control (Fl-02)
The high temperature limit control prevents the burner from
firing if excessive heated air temperatures are experienced. The
limit control is mounted on the blower housing and is electrically
interlocked with the gas controls. See page 21 for location. If
the limit control opens a service person must inspect the unit,
determine the cause, and take corrective action.
Figure 11.2 - high temperature limit control
Flame safeguard control (re-02)
All units are equipped with a flame safety control. This control
senses if the pilot flame has been established through the use
of a flame rod flame sensor.
The flame safeguard control has a built-in pre-purge timer, and
an ignition-timing device. The pre-purge timer allows the unit to
purge any residual gas in the unit before a try for ignition can
take place. The pre-purge time is approximately 10 seconds.
After pre-purge has occurred, the spark ignition sequence will
begin. If the pilot flame is not proved within the time period
allowed (10 to 25 seconds), the safeguard control will go into
lockout and will have to be manually reset before a new try for
ignition can occur.
Figure 11.3 - honeywell Flame safeguard control
7-500.10
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