Vermont Casting NVC39 User Manual

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14
NVC Series B-Vent 
20000194
Vent Safety Switch
This fireplace incorporates the use of a Vent Safety 
Shut-off Switch. The sensor and wiring are factory 
installed and should not be removed or altered during 
installation. 
In the event of total flue blockage the system will detect 
the increased heat buildup and will automatically shut 
down the main burner assembly.
The sensor is located above the firebox behind the top 
louvre assembly. It is accessible by removing the top 
louvre assembly.
CAUTION:  The firebox, Vent Safety Switch sensor 
and surrounding panels become very hot during 
normal operation. Allow time for the components to 
cool before carrying out any service or inspection.
If the sensor is activated and shuts off the burner as-
sembly, the following procedure should be followed:
• 
Observe that the pilot flame is still ON. If the pilot 
flame has gone out the reason for the fireplace shut 
down is not the vent safety switch.
• 
Turn the pilot flame OFF and close all controls. Allow 
the fireplace to cool.
• 
Check the flue and venting components for blockage 
or restrictions.
• 
Remove the front louvre assembly.
• 
Locate the sensor.
• 
Reset the sensor by pressing the reset pin between 
the two wire terminals. (Fig. 18)
CAUTION: The components may still be hot.
• 
Light the fireplace and check for downdrafts.
• 
Operate the fireplace in the normal manner. If the 
burner assembly shuts down again after a period 
of operation, DO NOT ATTEMPT TO RESET THE 
SENSOR AGAIN. 
Turn off the fireplace and contact 
your service technician.
Electrical Connection
The sensor is wired in series between the wall mounted 
ON/OFF switch and the Electronic Ignition Module (Fig. 
19) or the thermopile and the gas valve (Fig. 20)
FP1160
Vent safety switch
11/2/01  djt
Sensor
Wire Ter-
minal
Reset Pin
FP1160
Fig. 18  Vent Safety Switch.
Wire Terminal
24 VAC HOT
24 VAC RTN
ON-OFF
SWITCH
NOVA SIT 822 VALVE
HONEYWELL S8600 B IGNITION MODULE
120 VAC RTN
40VA 
TRANSFORMER
120 VAC HOT
BLACK
BLACK
BLACK
BLACK
BLACK
BLACK
BLACK
WHITE
WHITE
WHITE
WHITE
WHITE
WHITE
WHITE
WHITE
BLACK
FP670
NOVA SIT 822 VALVE WIRING DGRM. 
(w/ Honeywell S8600 B Ignition Module)
4/30/98
PILOT
  
H
I  
    
   
   
  
L
O
 
   
   
   
   
 
  
HI 
   
  
  
  
   
 L O 
     
     
    
E
A
  P
ILO
1  5
3  4
GREEN
MV     MVPV     PV GND
(BURNER)
24V
GND
24V
SENSE
SPARK
   
FP670
Fig. 19  Vent Safety Switch wiring, EN/EP units.
TH
TP
TH
TP
Gas
Valve
FP1161
Vent Safety Switch 
Wiring
11/2/01  djt
Thermopile
OnN/OFF 
Switch
Vent 
Safety 
Switch
FP1161
Fig. 20  RN/RP units using a remote ON/OFF switch.