Ametek Thermox 2000 ATEX Series User Manual page 142

AC Power Checks
Loss/Inadequate AC voltage to the sensor
Measure the AC voltage to the sensor board at terminals L1 and L2. Ensure
that this voltage is sufficient. Check the measurement technique used by
the volt meter (for example, RMS, average, peak, etc.). Specifications are
based on RMS measurements.
Furnace Checks
Open furnace
Disconnect power to the control unit and the sensor. With ohm meter,
measure across Terminals "R" and "S" on the sensor board. The resistance
of the furnace should be as follows:
32 ohms (±10%)
If the furnace resistance is not within allowable tolerances, replace the fur-
nace.
Loss of AC power to the furnace
Verify the correct line voltage at L1 and L2 of the sensor board.
With line voltage present, check the voltage at terminals R and S on the
sensor board. If voltage is present and the system is not heating, remove
power and check the furnace resistance (see "Furnace Checks" section). If
no voltage is present at terminals R and S on the sensor board, check for
the DC furnace drive signal at terminals 3 (+) and 4 (-) at the sensor board.
The furnace drive is a 15 VDC pulse train, and depending on the frequency
of the pulse train, the measured voltage will be between 5 and 15 VDC. If
this furnace drive signal is present, reset the power to the control unit and
see if this solves the problem. If this doesn't solve the problem, replace the
sensor board.
If the furnace drive signal is not present, check the interconnecting wir-
ing. If the interconnecting wiring is correct, check across FURNACE and
15V COM on the control unit wiring card for the furnace drive signal. If
the signal is not present, check fuse F1 on the wiring card. If this fuse is
OK, replace the control unit power supply/keypad module. If this fuse is
not OK, replace the fuse (1/4 amp, 125 volts, IEC speed type FF). Check the
interconnecting wiring for short circuits before applying power to the con-
trol unit.
6-14 | Thermox Series 2000 WDG-HPII / HPIIC - ATEX