Heatmaster
ss
G Series Furnace Operating Manual
26
G
SERIES
on the OUTPUT terminals, remove the 24V DC terminal strip
from the power supply and test for 24V DC on the output
pins. If there is not, the power supply is faulty and should be
replaced. If there is power on the pins with the terminal strip
removed then it is likely that there is a short circuit in the
24V DC wiring. Locate and repair the issue and re-install the
terminal strip.
Fan Motor Breaker:
•
If the fan motor breaker has tripped check the fan for
proper operation before resetting the breaker. Remove
and inspect the fan motor & wheel to confirm it is turning
freely.
Siemens LOGO Control: (with display)
•
Using an electrical test meter to 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 faulty and should be replaced.
•
If there is not 24V DC power at the terminals, check for
power output at the power supply.
Low Water Cut Off Switch:
Check to be sure there is enough water in the tank of the
furnace by removing the float assembly 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.
•
Use an electrical test meter to check for voltage across
the “M-“ and “I1” terminals on the Siemens LOGO control.
•
If the low water switch is satisfied (closed) there should be
24V DC.
•
If there is no voltage, power off the furnace, remove the
Low Water Switch wiring from the control 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. Remove 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:
Test the By-Pass Switch using an electrical test meter.
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 no 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. Check
that the switch is wired to the correct terminals and that
the magnet is within 1/2” of the sensor when the bypass
is in the closed position. 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 override the low temperature shut
down 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 Furnace Status should
change to “Cold Start Mode”. This message will remain
until the furnace has heated past it’s programmed cut in
temperature and the mode changes to “Heating Cycle”.
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” terminals 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.
Damper Actuator:
»
Inspect the top and bottom damper plates for proper
operation. The target damper position (%) is indicated
on the control screen. If the damper plate is not in the
