Heat Controller MGD Series, Руководство по обслуживанию

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MGD Gas Furnace Service Manual
DIAGNOSTIC FEATURES
This section describes the diagnostic features incorporated into the control. The furnace
electronic controls utilize an on-board LED to transmit a diagnostic flash code, which may be used
in troubleshooting system problems. The table below describes these codes.
Table of Diagnostic Codes
FLASHES FAULT CONDITION CHECK
STEADY ON NORMAL OPERATION
1 IGNITION FAILURE (ONE HOUR LOCKOUT) GAS FLOW, GAS PRESSURE, GAS VALVE, FLAME SENSOR
2 CLOSED PRESSURE SWITCH PRESSURE SWITCH STUCK CLOSED
3 PRESSURE SWITCH FAILED TO CLOSE VENTER, PRESSURE SWITCH, VENT BLOCKAGE
4 LIMIT SWITCH OPEN MAIN LIMIT, AUX. LIMIT
5 GAS VALVE ENERGIZED WITH (W) OFF GAS VALVE
RAPID FLASH INCORRECT LINE VOLTAGE PHASING L1 AND L2 CONNECTIONS REVERSED
LIMIT SWITCHES
Two different kinds of limit switches are used on the MGD series of gas furnaces. They are the
main limit (manual re-set) and the auxiliary limit (automatic re-set) and are used on ALL models.
Typical Limit Switch
It must be remembered, that a limit switch is a safety device and other than for testing purposes,
limit
switches should never be jumped out Limit switches are normally closed electrical
switches that are designed to open when their pre-determined limit setting has been reached. It
should also be remembered, that when a limit switch opens, it more than likely is not due to a bad
switch!
The cause of the opening limit must be found and corrected, before the furnace can resume
proper operation.
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