Midco Economite RE4400DS - Manual (Page 10)

? 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.
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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.
? Cleaning of the blower wheel is usually the only service required. Need for cleaning is
indicated if the character of the flame indicates a deficiency of air. Motor cooling air vents (if
present) should also be cleaned at this time.
? The motor and wheel are removed as an assembly. Disconnect the motor conduit from
the motor and remove the mounting bolts.
? The burner is equipped with a diaphragm type air pressure switch so as to prevent the
burner from firing if the blower wheel is not running at its operating speed. When the motor is
off there is no air pressure present to activate the pressure switch and in turn there is no
power flow to the Electronic Control.
? To make a specific test of the interlock circuit:
1. Turn burner power OFF.
2. Turn Manual Gas Cock OFF.
3. Disconnect the motor wire from the terminal strip to keep the motor off.
4. Turn burner power ON and set the operating control to ON or thermostat to call for
heat. Verify there is 120VAC line voltage by using a multimeter. Check for 24V
between the Electronic Control 25V and 25V GND terminals.
A. No voltage: Interlock circuit OK.
B. Voltage present: check that the switch is wired properly or check switch
operation. Replace if switch tests bad.
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? Should replacement or service be required, valve manufacturer's instructions must be
followed as outlined in their information sheet.
? Outlet pressure settings must be checked while the gas is flowing.
? 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.
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? The RE4400DS and RE4400DSA operate when power is applied to L1 and L2 through a
safety and or operating control. With power applied to L1 and L2 the blower motor starts.
Once the diaphragm air flow switch proves blower operation power is applied to the S87
Electronic Control. The S87 Electronic Control provides the switching of the gas valve and
ignition sequence. If the flame signal is above 2DC micro amps the RE4400DS and
RE4400DSA will remain in operation until a safety or operating control opens the circuit to
L1 and L2. For a more thorough explanation of the Honeywell electronic control refer to the
literature provided with the power burner. For startup information see section VIII.
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? The S87 is a low voltage, solid state, direct spark ignition control module for gas-fired
furnaces, boilers and heating appliances. UL Listed models are only available with a pre-
purge timer. The S87 controls the gas valve, monitors the main burner flame and
generates a high voltage for spark ignition.
? The S87K uses separate electrodes for spark ignition and flame sensing. Use with any
gas control designed for DSI application that is rated at 2.0 A or less. Includes a 30 second
10
Part 2
Service Continued
Part 2 Service
Figure 8: Motor / Blower Assembly
XI Valve Train
XII Sequence of
Operation
XIII Electronic
Control
X Motor Blower
Interlock
IX Electrodes
Continued