17
7. Standing Pilot Model M1G
SEQUENCE OF OPERATION FOR STANDING PILOT
a
On a call for heat, the thermostat contacts close, supply-
ing 24 VAC to the gas valve.
b.
When the gas valve is energized it steps open at a
reduced flow and opens fully after approximately 14
seconds.
c.
When the call for heat is satisfied the thermostat contacts
open, the gas valve shuts off gas flow.
SEQUENCE OF OPERATION FOR STANDING PILOT W/
INDUCED DRAFT BLOWERS
a.
On a call for heat, the thermostat contacts close, supply-
ing 24 VAC to the relay.
b.
The relay contacts close and energize the induced draft
motor.
c.
When the motor reaches full speed the pressure switch
closes and energizes the gas valve.
d.
When the gas valve is energized it steps open at a
reduced flow and opens fully after approximately 14
seconds.
e.
When the call for heat is satisfied the thermostat contacts
open, the gas valve shuts off gas flow, and the induced
draft blower stops.
TROUBLESHOOTING
Polarity and Ground
The furnace will not operate if loss of ground occurs. Every
effort should be made at the installation to provide a good
ground. If old 2-wire romex exists it should be replaced with a
2-wire w/ground. A cold water line could be used provided that
the connection or grounding occurs before any di-electric
fittings and provided no plastic pipe is used inside or outside
the building.
Transformer (Picture 3)
All M1G furnaces are protected by a fuse in the 24 vac circuit.
The transformer supplies control voltage (24 vac) by stepping
down the supply (primary) voltage from 115 vac to 24 vac
(secondary voltage). All M1 transformers are rated at 30 VA.
VA is the volt/amp or total wattage the secondary can handle.
When a transformer is replaced, the VA should be at least 30
VA, but no more than 40 VA.
Check-out procedure:
1.
Using a volt/ohmmeter on at least 115 vac scale.
2.
Measure the voltage at the primary side.
3.
If voltage is 115 vac measure the voltage at the secondary
terminals marked "24 vac" & "Com" on the transformer.
4.
If 115 vac is measured at primary but no voltage is present
at "24 vac" & "Com", replace transformer.
5.
Fuse will blow if a secondary short occurs.
Transformers open on secondary indicate an overload (a
current draw that exceeded rating).
Picture 3. Transformer
Transformer
Fuse
On-Off Switch (Picture 4) – This switch turns electrical
power to the furnace on and off. The switch must be set in the
“On” position for the furnace to operate. For M1G* models, in
warm weather there is a possibility of the blower coming on
periodically or operating continuously due to a heat buildup
within the furnace by a combination of warm weather and heat
from the pilot. This is normal operation as long as there is
power to the furnace and the On-Off switch is at the “ON”
position. If blower operation is not desired, the On-Off switch
may be set in the “OFF” position to cut the electrical power to
the furnace.
GROUND
NEUT.
HOT
OK
VOLTS AC
VOLTS DC
OHMS
MICRO
AMPS
Volts
Com
Prep
GROUND
NEUT.
HOT
HOT NEUTRAL
VOLTS AC
VOLTS DC
OHMS
MICRO
AMPS
Volts
Com
Prep
Polarity may be verified as follows:
1. Turn power supply "ON"
2. Using a voltmeter, check for
voltage between the hot (black)
and neutral (white) wire of
supply circuit.
3. Reading should be Line (Supply)
Voltage.
4. Check for voltage between the
neutral (white) wire and ground
wire of the supply circuit.
5. Reading should be zero volts (if
line voltage is read, polarity is
reversed).
6. Double check by checking for
voltage between the hot (black)
wire and ground wire of the
supply circuit.
Figure 14. Polarity and Ground
Picture 4. On-Off Switch
