Electrical Troubleshooting - Heatmaster G100 Operation And Maintenance Manual

Electrical troubleshooting should always be done by a qualified technician
High Limit Switch:
Using an electrical testing meter check for power on both poles of the high limit switch.
If the furnace temperature is above 195 F. the switch should be OPEN and there should
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only be power on one pole of the switch. If the furnace was over 195 F. and the switch has
opened the water will need to cool down to approximately 140 F. before it will close and allow
power through once again.
If the furnace has not over heated (190 F.+) but there is still power on only one pole of
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the switch, the switch is faulty and should be replaced.
If there is not power on either pole check for power at the main power switch at the rear
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of the furnace.
Control power supply switch:
Using an electrical testing meter check for power on both poles of the power supply rocker
switch. The switch has power in, neutral, and power out poles. During normal operation there
should be power at the power in and power out poles.
If there is only power on one of the poles check to make sure the switch is in the "on" position.
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If the switch is "on" and there is only power on one pole the switch is faulty and should be
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replaced.
If there is not power on either the power in or the power out pole check for power at the
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high limit switch.
Siemens 24V DC Power Supply:
Using an electrical testing meter check for DC voltage at the OUTPUT terminals.
If there is 24 volts DC across the terminals and the green LED on the front is lit the power
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supply is working.
If there is not 24 volts DC check for power on the INPUT terminals (this should be 115V
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AC)
If there is 115V AC on the INPUT terminals but not 24V DC on the OUTPUT terminals the
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power supply is faulty and should be replaced. Check for possible short circuits in the 24V
DC wiring that may have caused the power supply to fail.
If there is not 115V AC on INPUT terminals check for power at the Control Power Switch.
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1 Amp fuse:
Using an electrical testing meter check for 24V DC on the output lead from the fuse holder.
If there is 24V DC on the output lead then the fuse is good.
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If there is not 24V DC on the output lead then remove the fuse from the fuse holder
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and check for continuity across the fuse. If there is not continuity the fuse has blown and
should be replaced. Check for possible causes such as a short circuit in the wiring.
If there is continuity across the fuse check for 24V DC power in the input lead to the fuse
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holder. If there is power there then check the fuse holder to be sure the fuse is seating proper-
ly.
If there is not 24V DC power on the input lead to the fuse holder, check for power at the
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Control Power Supply.
Siemens LOGO Control: (with display):
Using an electrical testing meter check for 24V DC power across the "L+" and "M-" terminals.
If there is 24V DC power at the terminals but the display remains blank the control is
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faulty and should be replaced.
If there is not 24V DC power at the terminals, check the 1 AMP fuse that supplies power
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to the control.
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TROUBLESHOOTING

Electrical Troubleshooting

G Series Outdoor Furnaces
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