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119344-01B

0

OBSERvED PROBLEM

ODS/pilot  lights  but  flame 
goes  out  when  control  knob 

is released

Burner  does  not  light  after 
ODS/pilot is lit

Delayed ignition of burner

Burner backfiring during com

-

bustion

REMEDY

1. Press in control knob fully

2. After ODS/pilot lights, keep 

control knob pressed in 30 

seconds

3. Wait one minute for safety 

interlock  system  to  reset. 

Repeat ignition operation

4. Fully open equipment shut

-

off valve

5. Hand  tighten  until  snug, 

then tighten 1/4 turn more

6. A) Contact local natural or 

propane/LP gas company

  B)  Clean  ODS/pilot  (see 

Cleaning and Maintenance

page 18) or replace ODS/

pilot assembly 

7. Replace pilot assembly
8. Replace control valve

1. Clean burner (see 

Cleaning 

and Maintenance

, page 18) 

or replace burner orifice

2. Contact  local  natural  or 

propane/LP gas company

1. Contact  local  natural  or 

propane/LP gas company

2. Clean burner (see 

Cleaning 

and Maintenance

, page 18) 

or replace burner orifice

1. Clean burner (see 

Cleaning 

and Maintenance

, page 18) 

or replace burner orifice

2. Replace burner
3. Replace gas regulator

POSSIBLE CAUSE

1. Control  knob  not  fully 

pressed in

2. Control knob not pressed in 

long enough

3. Safety interlock system has 

been triggered

4. Equipment shutoff valve not 

fully open

5. Thermocouple  connection 

loose at control valve

6. Pilot  flame  not  touching 

thermocouple,  which  al

-

lows thermocouple to cool, 
causing  pilot  flame  to  go 
out. This problem could be 
caused  by  one  or  both  of 
the following:

  A) Low gas pressure
  B) Dirty or partially clogged 

ODS/pilot

7. Thermocouple damaged
8. Control valve damaged

1. Burner orifice is clogged

2. Inlet  gas  pressure  is  too 

low

1. Manifold  pressure  is  too 

low

2. Burner orifice is clogged

1. Burner orifice is clogged or 

damaged

2. Burner damaged
3. Gas regulator defective

TRoUBlesHooTING

Continued

Summary of Contents for WMN20A

Page 1: ...her flammable vapors and liquids in the vicinity of this or any other appliance WHAT TO DO IF YOU SMELL GAS Do not try to light any appliance Do not touch any electrical switch do not use any phone in...

Page 2: ...er or birth defects or other reproductive harm IMPORTANT Read this owner s manualcarefullyandcompletely before trying to assemble operate or service this heater Improper use of this heater can cause s...

Page 3: ...th other gases 2 Do not place propane LP supply tank s inside any structure Locate propane LP supply tank s outdoors 3 This heater shall not be installed in a bedroom or bathroom 4 If you smell gas sh...

Page 4: ...f the unit Vent free gas products are prohibited for bedroom and bathroom installation in the Commonwealth of Massachusetts Unpacking 1 Remove heater from carton 2 Remove all protective packaging appl...

Page 5: ...The air that leaks around doors and windows may provide enough fresh air for combustion and ventilation However in buildings of un usually tight construction you must provide additional fresh air Unus...

Page 6: ...ppliances Direct vent draws combustion air from the outdoors and vents to the outdoors Example Gas water heater _ ____________ Btu Hr Vent free heater _ ___________ Btu Hr Total _ ___________ Btu Hr 4...

Page 7: ...lheatingsystem youmay run system s circulating blower whileusingheater Thiswillhelp circulatetheheatthroughoutthe house In the event of a power outage you can use this heater as your primary heat sour...

Page 8: ...affic areas in windy or drafty areas Figure 4 Mounting Clearances As Viewed From Front of Heater INSTALLATION Continued CAUTION This heater cre ates warm air currents These currents move heat to wall...

Page 9: ...of front panel forward then out 3 Remove any remaining packaging ma terials Methods For Attaching Mounting Bracket To Wall Only use last hole on each end of mounting bracket to attach bracket to wall...

Page 10: ...cm 5 6 cm 18 3 4 47 6 cm Min 18 3 4 47 6 cm Min Figure 10 Popping Open Anchor Wings For Thin Walls Mounting Bracket attached to wall Horizontal Slots Attaching To Wall Anchor Method For attaching moun...

Page 11: ...lace front panel at this time Replace front panel after making gas connections and checking for leaks see pages 12 through 14 INSTALLATION Continued Mounting heater to floor With optional floor kit Mo...

Page 12: ...ure 14 External Regulator With Vent Pointing Down External Regulator Propane LP Supply Tank Vent Pointing Down CAUTION Use only new black iron or steel pipe Inter nally tinned copper tubing may be use...

Page 13: ...ernal regula tor has been installed between propane LP supply and heater See guidelines under Connect ing to Gas Supply page 12 Pressure Testing Gas Supply Piping System Test Pressures In Excess Of 1...

Page 14: ...tank valve 3 Make sure control knob of heater is in the OFF position 4 Check all joints from equipment shutoff valve to thermostat gas valve see Figure 17 or 18 Apply a noncorrosive leak de tection f...

Page 15: ...losion may result causing property damage per sonal injury or loss of life A This appliance has a pilot which must be lighted by hand When lighting the pi lot follow these instructions exactly B BEFOR...

Page 16: ...temperatures etc Frequent use of your heater will let you determine your own comfort levels MANUAL LIGHTING PROCEDURE 1 Remove front panel see Figure 7 page 9 2 Follow steps 1 through 7 under Lighting...

Page 17: ...eck pilot flame pattern and burner flame pattern often PILOT FLAME PATTERN Figure 22 shows a correct pilot flame pattern Figure 23 shows an incorrect pilot flame pat tern The incorrect pilot flame is...

Page 18: ...ommend that you keep the burner tube and pilot assembly clean and free of dust and dirt To clean these parts we recommend using compressed air no greater than 30 PSI Your local computer store hardware...

Page 19: ...position 4 Air in gas lines when in stalled 5 Depleted gas supply pro pane LP gas only 6 ODS pilot is clogged 7 Gas regulator setting is not correct OBSERVED PROBLEM Whenignitorbuttonispressed there...

Page 20: ...ane LP gas company 1 Contact local natural or propane LP gas company 2 Clean burner see Cleaning and Maintenance page 18 or replace burner orifice 1 Clean burner see Cleaning and Maintenance page 18 o...

Page 21: ...s from furniture polish wax carpet cleaners etc may turn into white powder residue 1 Metal expanding while heat ing or contracting while cooling REMEDY 1 Check burner for dirt and debris If found clea...

Page 22: ...partially clogged 1 Gas leak See Warning statement above 2 Control valve defective 1 Foreign matter between control valve and burner 2 Gas leak See Warning statement above 1 Not enough combustion vent...

Page 23: ...ced under warranty Parts Under Warranty Contact authorized dealers of this product If they can t supply original replacement part s call DESA Heating Products Technical Ser vice Department at 1 866 67...

Page 24: ...119344 01B 24 4 20 4 17 18 19 2 3 5 6 8 16 9 10 11 12 13 14 18 Manual Control Models Only Thermostat Models Only 19 7 1 21 22 15 9 Illustrated Parts Breakdown Models WMN20A WMP20A GWN20TA GWP20TA GWN...

Page 25: ...bly 1 107894 15 Deflector Assembly 1 9 098271 09 Ignitor Cable 1 10 098249 01 Nut 2 11 110803 01 ODS Pilot Assembly 1 110803 02 ODS Pilot Assembly 1 12 103446 02 Burner 1 103447 06 Burner 1 13 099387...

Page 26: ...GA5010 For all models Equipment shutoff valve with 1 8 NPT tap FAN KITS PP100 For all models Provides better heat distri bution Makes heater more efficient Com plete installation and operating instru...

Page 27: ...1 0505 1 800 446 1446 www nbmc com Parts Centrals These Parts Centrals are privately owned businesses They have agreed to support our customer s needs by providing original replacement parts and acces...

Page 28: ...Heating Products who will provide original factory replacement parts Failure to use original factory replacement parts voids this warranty The heater MUST be installed by a qualified installer in acc...

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