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26

TiME linE

DESCripTiOn

Start Time

Thermostat Calls for Heat

The wall thermostat controls the operation of the furnace by reacting to room temperature.  This 

allows current to flow through the ON/OFF switch to the module board.

The module board constantly checks for a minimum 9.5 volts.  if there is not 9.5 volts, the 

module board will go into a stand by mode until adequate power is supplied.  it will then resume 

normal operation.

upon a call from the thermostat, the module board thermostat circuit will go active.  The sail 

switch circuit is verified as being open.  The blower output is energized.  Blower motor starts.

15 Seconds Purge Cycle

The module board will then verify that the sail switch circuit is closed and motor is up to speed. 

if this circuit remains open for 30 seconds after the blower motor starts, the module board will 

go into lockout mode and shut down the blower motor.

The module board checks that the gas valve relay contacts (which are located on the module 

board) are open before the ignition sequence starts.

The  board  has  a  pre-purge  timing  circuit  of  approximately  15  seconds.  This  allows  the 

combustion chamber to purge.

7 Seconds Ignition Cycle and 

Flame Sense

The module board will energize the gas valve and enable the high voltage spark output to the 

electrode for seven (7) seconds of ignition time.

The  module  board  will  then  check  for  flame  sense  to  verify  successful  lighting  of  the  main 

burner  flame.  Sparking  of  the  igniter  will  then  be  terminated  and  the  gas  valve  and  blower 

outputs will remain energized.

if ignition is successful the module board will monitor the flame sense, sail switch and limit 

switch circuits, and the thermostat inputs during the heating period.

The flame is sensed through the spark wire and electrode. Therefore, it is essential that the 

electrode is properly positioned in the burner flame.

2nd and 3rd Ignition Cycles if 

Required

3 Try Ignition Board

if the flame is 

not

 sensed after seven (7) seconds, a second 15 second purge cycle will begin 

followed by a second Trial-For-ignition sequence. After three (3) Trial-For-ignition attempts with 

no ignition of the main burner, the module board will de-energize the gas valve immediately and 

blower will run for 3 minutes and then shutdown in lockout mode.

Heating Cycle

if during the heating cycle, the limit switch circuit opens and remains open for 5 minutes, the 

module board will go into lock out and shut down the blower motor. if this occurs, the thermostat 

will need to be reset for the furnace to operate.

90 Second Shut Down

When the thermostat has reached its set point and the demand for heat ends, the gas valve will 

be de-energized and the flame will go out. The post purge period of 90 seconds begins. When 

it times out, the blower motor output is removed, and the blower stops.

SEQuEnCE OF OpEraTiOn

FOr Fan COnTrOl MODulE bOarD

parT nuMbEr 520820

Summary of Contents for SFV-25

Page 1: ...Suburban R V F URNA C E Service TRAINING Manual...

Page 2: ...12 VDC 520820 Fan Control Module Board 26 Sequence of Operation 24 VAC 520947 Fan Control Module Board 27 Sequence of Operation SHD 2542 Furnace 28 Sequence of Operation Time Delay Relay Equipped Fur...

Page 3: ...erates on 120 volts AC These are designed and tested under the same standards as the 12 volt models Suburban forced draft combustion furnaces used in recreational vehicles are designed for use with Pr...

Page 4: ...ved from the furnace 3 Never use a screwdriver on any part of the electrode assembly while the furnace is in operation 4 Be certain that the spark from the electrode never reaches the flame sensor por...

Page 5: ...1 2 17 20 Electronic 35 SF 42Q 42FQ 40 000 7 1 2 17 20 Electronic 35 SH 35Q 35FQ 35 000 9 1 4 17 20 Electronic 40 SH 42Q 42FQ 40 000 9 1 4 17 20 Electronic 42 Accessories Description 6258ACW DOOR Opt...

Page 6: ...all controls and applicable parts 6 To re install reverse this procedure 7 Rewire applicable wires and perform a leak test on all fittings Perform a drop pressure test NT 12 16 20SE 1 Turn off gas and...

Page 7: ...essary 2 Remove the vent cap assembly by removing applicable screws 3 Remove the cabinet front two 2 screws 4 Remove the 1 one tie down screw securing the chamber to the cabinet 5 Remove the furnace f...

Page 8: ...furnace installation manual for all installation requirements Location and Installation Locate the furnace near lengthwise center of the coach Choose a location for installation out of the way of wire...

Page 9: ...P AND ACROSS CENTER AS SHOWN CENTER PUTTY STRIP IS ESSENTIAL OUTSIDE SKIN PANEL TUBE INTAKE AIR WITH GASKET VENT CAP AND EXHAUST DETAIL A 2 MAXIMUM WALL THICKNESS TUBE AIR INTAKE WITH GASKET VENT CAP...

Page 10: ...INSIDE FURNACE COMPARTMENT APPLY CAULKING GENEROUSLY AROUND PERIMETER OF VENT CAP AND ACROSS CENTER AS SHOWN CENTER PUTTY STRIP IS ESSENTIAL 2 M A X C L 9 7 64 1832 7 10 1 32 FURNACE TIE DOWN SCREW FU...

Page 11: ...DERED SEPARATELY EXTENSION KITS COME WITH COMPLETE INSTALLATION INSTRUCTIONS 1 Figure 4A SH Models VENT ASSEMBLY INSTALLATION SF 20F SF 25F SF 30F SF 35F SF 42F STANDARD VENT INSTALLATION X INTAKE 1 2...

Page 12: ...MUST BE NOTCHED AS SHOWN BELOW 220 MIN HEIGHT WIDTH DETAIL A ONE PER SIDE CABINET MOUNTING L C 375 2 062 220 MIN 2 060 8 281 CUTOUT AS VIEWED FROM OUTSIDE R V CUTOUT FOR FURNACE ACCESS DOOR FRAME FLO...

Page 13: ...URE WITH 6 SCREWS REMOVABLE PANEL OF COACH WALL MUST SEAL WATER TIGHT WITH GASKET C L L CFURNACE CUTOUT ANCHOR FURNACE TO FLOOR USING THE 4 10 X 3 4 SCREWS PROVIDED 2 2 250 DIA HOLES 2 000 MAX WALL TU...

Page 14: ...ENT CAP AND ACROSS CENTER AS SHOWN CENTER PUTTY STRIP IS ESSENTIAL IMPORTANT VENT CAP AND TUBE ASSY MUST BE INSTALLED FROM OUTSIDE OF COACH VENT ASSEMBLY INSTALLATION NT SERIES VENT TUBE INSTALLATION...

Page 15: ...12 1 1 4 MIN OVERLAP 3 8 X 27 1 4 TO 29 1 2 22 3 4 TO 25 25 TO 27 1 4 TRAILOR SKIN 2 1 4 VENT CAP 1 2 MIN OVERLAP DIA 2 1 4 Y 7 1 2 DIA VENT TUBE INSTALLATION NT 20S VENT TUBE ASSY INTAKE SEE CHART MO...

Page 16: ...20501 7 to 9 EXTENSION TUBE KIT NUMBER MIN MAX LENGTH Extension Tube Range 520593 2 1 4 to 3 1 8 520594 3 1 8 to 4 7 8 520595 4 7 8 to 7 520596 7 to 9 Figure 15 NT 40 P40 Figure 14 NT 24 30 34SP P30 3...

Page 17: ...WALL THICKNESS 2 25 NOTE 0 CLEARANCE PERMISSIBLE AT REAR OF FURNACE FOR A WIDTH OF 2 25 MAXIMUM VENT CAP Figure 17 P40 VENT ASSEMBLY INSTALLATION NT40 P40 3 1 2 7 1 2 2 3 4 13 6 7 32 12 7 16 FLOOR 1...

Page 18: ...NOT REMOVE COLLAR VENT CAP CENTERLINE OF FURNACE INSTALLATION 3 DIA 2 HOLES OUTER SKIN 3 1 2 X 7 CUTOUT THRU COMBUSTIBLE CONSTRUCTION CAULK BEHIND VENT CAP AS SHOWN TO SEAL BETWEEN EXHAUST AND INTAKE...

Page 19: ...THE FURNACE MUST NOT BE LESS THAN THE MINIMUM SPECIFIED SPACER BUMPS FURNACE Figure 20 SF 20F 25F 35F 42F DUCTING Suburban furnaces require that a minimum duct area be maintained throughout entire du...

Page 20: ...L R SIDE DUCT SQ INCH RETURN AIR SQ INCH DD 17DSI SEE 1 0 0 0 0 0 N A N A N A N A N A NT 12S 3 8 1 0 0 1 1 2 4 N A N A 25 55 NT 16S 3 8 1 0 0 1 1 2 4 N A N A 25 55 NT 20S 1 1 0 0 1 1 2 4 N A N A 25 5...

Page 21: ...REQ D BTM DUCT SQ INCH TOP DUCT SQ INCH L R SIDE DUCT SQ INCH RETURN AIR SQ INCH SF 20 20F 1 0 0 0 0 0 2 4 56 56 25 55 SF 20Q 20FQ 1 0 0 0 0 0 2 4 56 56 25 55 SF 25 25F 1 0 0 0 0 0 3 4 56 56 36 55 SF...

Page 22: ...BACK CLR LEFT CLR RIGHT DUCTS REQ D BTM DUCT SQ INCH TOP DUCT SQ INCH L R SIDE DUCT SQ INCH RETURN AIR SQ INCH SFV 20 20F 1 1 0 0 1 1 SEE 4 52 SEE 4 SEE 4 55 SFV 25 25F 1 1 0 0 1 1 SEE 4 52 SEE 4 SEE...

Page 23: ...any of the original wire that is supplied with the appliance must be replaced it must be replaced with type 105 C or its equivalent Power supply connections are to be on the right side of the furnace...

Page 24: ...ucted 16 000 PROPANE 12 VDC 3 2 8 1 WC 165 NT 20S Ducted 19 000 PROPANE 12 VDC 3 2 8 1 WC 165 NT 12SE Direct Discharge 12 000 PROPANE 12 VDC 3 2 8 N A 140 NT 16SE Direct Discharge 16 000 PROPANE 12 VD...

Page 25: ...3 7 0 3 IN MOTOR 2 WC 300 SF35 35F Ducted 35 000 PROPANE 12 VDC 3 8 5 2 5 IN MOTOR 9 4 3 IN 2 WC 375 SF35Q 35FQ Ducted 35 000 PROPANE 12 VDC 3 8 4 3 IN MOTOR 2 WC 375 SF 42 42F Ducted 40 000 PROPANE...

Page 26: ...module board will then check for flame sense to verify successful lighting of the main burner flame Sparking of the igniter will then be terminated and the gas valve and blower outputs will remain en...

Page 27: ...seconds of ignition time The module board will then check for flame sense to verify successful lighting of the main burner flame Sparking of the igniter will then be terminated and the gas valve and b...

Page 28: ...ame sense to verify successful lighting of the main burner flame Sparking of the igniter will then be terminated and the gas valve and blower outputs will remain energized If ignition is successful th...

Page 29: ...em as power is applied to the DSI Board The system will do the following 1 The board has a timing circuit which allows the blower to purge the chamber of any products of combustion or gas 2 The board...

Page 30: ...fifteen 15 seconds the module creates spark and opens valve NO Check for 12VDC between RED and YELLOW wires at the module board YES Check plug connection tot he Module Electrode and Wire Spark gap 1...

Page 31: ...Molex Edge Connector YES Verify voltage thru limit and sail switch to module board If circuit remains open for 30 seconds module board will go into lockout and shut down motor RESET thermostat Replac...

Page 32: ...ockout function of the module board After the blower has stopped the ignition sequence can be started again The module will try three times for ignition before lockout It is important to determine the...

Page 33: ...ator behind module board is in place d Make certain that the transformer voltage is within 24 30 volts A C e Be sure duct connections to furnace are airtight Seal duct collar connections to furnace ca...

Page 34: ...WIRE UL 3257 P 40 340312 TRANSFORMER THERMOSTAT TIME DELAY RELAY LIMIT SWITCH N C G CAPACITOR BR BR W MOTOR MODULE BOARD ELECTRODE BK BK G W G W DISCONNECT BLOCK BR G Y Y BR GROUNDING TERMINAL SAIL SW...

Page 35: ...VOIDS WARRANTY OF FURNACE UNIT 100 FIRE CHECKED NOTE ELECTRODE SAIL SWITCH N O SW N C LIMIT Y Y Y GROUNDING TERMINAL BR BK MOTOR VALVE SWITCH N C BL BK BK Y BR R Y O R BL THERMOSTAT R 12 V D C Y 12 V...

Page 36: ...ARD ELECTRODE GROUNDING TERMINAL BL THERMOSTAT R 12 V D C Y 12 V D C BL THERMOSTAT MOTOR SWITCH SAIL N O ELECTRODE MODULE BOARD V V 340512 14 AWG 105 C THERMOPLASTIC NO 18 250 C RADIX WIRE UL 3257 APP...

Page 37: ...rts in the top of the burner c Using a black felt tip pen mark a line along top of burner 3 16 from back of lance and parallel with lance Make an additional mark indication center line of the lance Se...

Page 38: ...r it is important for the electrode to be positioned properly over the top of the burner When replacing the electrode or should you be experiencing ignition type problems the electrode should be posit...

Page 39: ...t if a furnace has not been used it will not require cleaning NOT SO A furnace which has not been used for some time could be more in need of cleaning than a furnace which has been used extensively Du...

Page 40: ...676 Broadway Street Dayton Tennessee 37321 423 775 2131 Fax 423 775 7015 www RVComfort com All information published in this manual is subject to change without notice Suburban Division...

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