710 / 710 ASME Service Manual
Ver. 1.00
16
CONFIDENTIAL
10-2. Gas manifold
Unit Part #
#120
AOS Part #
319143-305 (LP model)
319143-306 (NA model)
Checkpoint
N/A
Function
1. The manifold distributes gas from the gas valves to the burners. The
manifold has two types of the nozzles: one type for gas-rich burners (20
nozzles) and the other for air-rich burners (19 nozzles)
2. There are 3 zones within the manifold, to ensure efficient combustion
operation.
Failure event
1. Dust deposit on the manifold.
2. Gas leakage from a failed manifold.
3. Ignition failure.
4. Imperfect combustion.
Effects on the water
heater if the manifold
fails
1. The burners cannot receive proper gas flow from the manifold, which can
cause poor combustion in the combustion chamber. In this case, the AFR rod
will detect an improper flame condition and computer will take safety
measures.
2. Gas leakage from the manifold.
Error codes when the
manifold fails
101
111
121
991
Diagnostic
1. Visual inspection: Excessive dust deposit around the nozzles or cracks on
the manifold.
2. Check voltages and resistance: proper range of values shown below.
Color / Number of wires
Blue-Red
78 to 100 VDC / 0.9 to 1.7
kΩ
Nozzles for air-rich burners
Nozzles for gas-rich burners
319143-305 (for LP model) and 319143-306
(for NA model) is an assembly of the gas
manifold with the gas valve assembly. For
safety reasons, these assemblies should be
installed in the unit as a whole set.
The gas manifold has the “33T” mark on the
manifold plate.
1 0 - 7 / 8 " ( 2 7 7 m m )
7
-
7
/
8
"
(
2
0
3
m
m
)
3 3 T
"3 3 T " m a r k
