Midco Economite RE6850B - Manual (Page 12)

Part 2 Service
DANGER: Do not
tamper with the unit or
controls. If trouble occurs
contact the installing
contractor, service agency,
or fuel supplier. See front
cover.
DANGER: Be sure
that the main and pilot
manual Shut-Off Valves are
closed and the burner
power supply is turned off
before removing any parts for service.
CAUTION: Cover plates, guards, and enclosures must be maintained in place
at all times except during maintenance and service.
The pilot is of the premix, blast type. The full force of blower air is brought into the mixing tube
where the proper amount of gas is added through the pilot orifice. This mixture is discharged
through the pilot. The mixture provides the flame that contacts the flame sensing rod and also
ignites the main gas.
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CAUTION: Do not indiscriminately increase pilot orifice size. Pilot troubles are
rarely cured in this manner and new troubles may be created.
Under normal conditions, with a slight negative pressure in the combustion chamber, pilot
operating pressures should be set as indicated in Table 4.
Some conditions which may require a change from the normal setting include: extremely
long tubing connections between the regulator and pilot solenoid, high negative or positive
combustion chamber pressure, actual air shutter setting and altitude extremes.
Do not subject the pilot to an inlet pressure over 14.0"W.C. See Section VI PIPING for
high pressure gas.
To adjust outlet pressure, remove the seal cap for access to the adjusting screw. Turning
the screw clockwise will increase outlet pressure, counter clockwise will decrease outlet
pressure.
The spark rod for a natural gas burner is welded to a round 1/2” perforated retention plate.
(The spark rod for a propane gas burner is welded to a round 1/2” solid retention plate.) The
1/2” retention plate is centered in the 3/8” Tee pilot and is positioned so the high tension
voltage will arc to the inside of the 3/8” Tee pilot.(See Figure 6).
The flame sensing rod must be positioned as shown in Figure 6 so that the controller will
detect a proper flame.
Both the spark and flame rods are current carrying conductors and, along with their
connecting wires, must be kept free of contact with conductive metal parts of the burner. Rod
insulators and wire insulators should be clean, dry and free of cracks.
Both the spark and flame rods are made from heat resistant alloys and can be expected
to have a long service life. They should be routinely inspected, however, for corrosion or loss
of metal.
The pilot air tubing must be kept free of kinks or inside obstructions and must be positioned
per Figure 6, otherwise air flow could be reduced and adversely affect the pilot flame.
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CAUTION: BEFORE SERVICING, mark with a scribe line or measure opening
of air controlling shutter, so that it can be reset to its original position following
servicing.
Figure 7: Motor / Blower Assembly
Part 2
Service
Continued
12
X Motor Blower
Interlock
IX Pilot
6000
6000
6000 3.0"
to
4.5" W.C.
Model
RE 6 7 0 0
R E 6 8 5 0
R E 6 8 5 0 B 0.055"
0.055"
0.055"
Table 4: Pilot Specifications
Gas
Orifice
Diameter
#54
Wire Drill
Approx.
Capacity
BTU/Hr. Pilot Gas Pressure
2.5"
to
3.5" W.C.
Natural Propane