G Series Outdoor Furnaces
www.heatmasterss.com
TROUBLESHOOTING
Electrical Troubleshooting
Electrical troubleshooting should always be done by a qualified technician
Low Water Cut Off Switch:
Check to be sure there is enough water in the tank of the furnace by removing the float assem-
bly and looking in the fill pipe.
If the water level is low add enough to raise the water level so the float level shows full.
If the water level is full and the Low Water Alarm is flashing on the screen you will need to test
the low water switch.
Using an electrical testing meter check for voltage across the “M-“ and “I1” terminals on the
Siemens control. If the low water switch is satisfied (closed) there should be 24V DC.
- If there is not voltage, power off the furnace, isolate the low water switch from the control
and the wiring, then check for continuity across the switch.
- If the switch has continuity, re-install the wires in their original positions and power up the
furnace. The Low Water Alarm should disappear from the screen.
- If the switch does not have continuity, drain the furnace enough so that the water level is
below the low water switch and inspect the switch. If it is dirty it may be cleaned up, tested
and re-installed. If it is faulty it should be replaced.
By-Pass Door Switch:
To test the By-Pass Switch, use an electrical testing meter and measure the voltage across
the “M-“ and “I2” terminals on the Siemens control. There should be 24 VDC when the by-pass
is in the CLOSED position.
- If there is not power across those terminals, isolate the switch wiring and perform a continuity
test on the switch in the open and closed positions. The circuit should be “open” when
the by-pass is OPEN and “closed” when the by-pass is CLOSED.
- If this is not the case the switch must be inspected. The roof must be removed from the
furnace in order to inspect the switch. Check that the switch is wired to the correct terminals
and that the striker is depressing the switch plate accurately. If this is all working well but
there is no continuity across the switch when the By-Pass is CLOSED then the switch is
faulty and should be replaced.
Cold Start Button:
The cold start button will over-ride the low temperature cut-off feature of this furnace. It should
be pressed once to allow the furnace to operate when in a cold start situation.
If the screen is flashing “Low Temperature Alarm” and the Cold Start Button is depressed, the
alarm should be replaced with “Cold Start Override”. This message will flash until the furnace
has heated past 140 F.
- If the button is depressed and the “Low Temperature Alarm” continues the circuit should
be tested using an electrical testing meter. Check for voltage between the “M-“ and “I3” termi-
nals on the Siemens control when the button is DEPRESSED. There should be 24V DC
across those terminals only when the button is depressed.
- If there is no power present, isolate the switch from the control and wiring and check for
continuity across the switch. There should be continuity only when the button is depressed. If
not, the button is faulty and should be replaced.
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