Modine MDB Série Manuel D'installation Et De Maintenance page 12

control descriPtions
main Burner/Pilot safety Flame rods
A flame rod is a flame-sensing device that senses if the pilot
has been established using the flame rectification principle.
The flame rod monitors the pilot flame to assure it is
established. If a flame is present, the flame rod will send
an electrical signal to the flame safeguard control and allow
ignition of the main burner.
For units with burner lengths that are greater than three feet
(1925 MBH or greater), the burner assembly will include a flame
rod main flame sensor mounted at the burner end opposite the
pilot.
Figure 12.1 - Flame rod & Pilot/ignitor assembly
manifold Features
main Gas valve
All units are supplied with redundant automatic main gas shut-
off valves. These valves may be in the form of a combination
gas valve (having two valve seats in one valve body) or two
separate valves. The solenoid gas valves are electrically
operated and allow gas flow to the unit's modulating gas valve.
The motorized valve uses a hydraulic pump to open the valve
and includes a heavy-duty self-closing return spring for positive
shut-off in the event of a power loss to the valve. See page 17
for locations.
The type of main shutoff gas valve supplied with the unit
may vary depending on whether the unit was ordered with a
standard manifold or an FM or IRI manifold. To determine which
valve type was supplied, see the model number of unit shipped
and Table 12.1.
table 12.1 - main shutoff Gas valve type
mBh insurance combination
digit 9-12 digit 15 redundant
Up to 720 1, 2 or 3
Over 720
1, 2 or 3
to 2,500
1
Over 2.500 2
3
Digit 15:
1=ETL/IRI
2=FM less Restriction
3=FM with Restriction
12
main Gas valve Quantity by type
vG-05 vG-02 & vG-03
single single
solenoid motorized
1 n/a n/a
n/a 2 n/a
n/a 2 n/a
n/a 1
n/a n/a
Figure 12.2 - combination Gas valve (vG-05)
Figure 12.3 - single solenoid and motorized Gas
valves (vG-02/03)
SINGLE SOLENOID VALVE
Pilot Gas solenoid Gas valve (vG-01)
The pilot solenoid gas valve serves as a separate shut-off
valve for the pilot gas. See page 17 for locations.
combination high/low Gas Pressure switch
(Ps-04/07)
When required by local codes, a combination high/low gas
pressure switch can be added to the unit controls. The switch
monitors the gas pressure downstream from the safety gas
shut-off valves in the case of high gas pressure, and ahead of
all of the automatic gas valves in the case of low gas pressure.
The gas pressure safety switches will shut off all electric
power to the gas safety shut-off valves if excessive (high
pressure switch) or low gas pressure (low pressure switch) is
experienced. A combination high/low gas pressure switch is
standard for FM manifolds over 2500MBH (Digit 9-12>2500
and Digit 15=2 or 3).
Figure 12.4 - high/low Gas Pressure switch
1
2
7-500.10
SINGLE MOTORIZED VALVE