Rumbling noise from gas furnace Exch

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  #1  
Old 02-25-02, 02:56 PM
sumarpatel
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Rumbling noise from gas furnace Exch

I have a large York natural gas furnace (180 BTU). Lately there is a large rumbling noise from the heat exchanger when the thermostat calls for heat. The noise goes away when the blower fan comes on. The noise is less when the fan is set to be continuously on. I have had couple of servicemen look at this without any results. The furnace was serviced 6-7 moths ago.
 
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  #2  
Old 02-26-02, 02:35 PM
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PLease

watch the flame when unit kicks in---let us know its flame pattern--if you have a 4 burner set up make sure all burners have flame---make sure burner flames are steady and blue AND not lifting--please supply as much info as possible and give us a holler back.PDF
 
  #3  
Old 02-27-02, 06:59 AM
sumarpatel
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There are 5 burners, they all have flames. The flames are not steady all the time and do flicker. They are deep blue at the base and lighter blue above. However there are streaks of yellow; in 2 or 3 burners more so than others. These streaks are not continuous - they come and go. I tried increasing the primary air, went to the max, but the yellow streaks remained. The burners stay on for 2 to 3 minutes at a time while the thermostat is still calling for heat.
Why are the burners going off (cycling) so often? Is this what's supposed to happen? My manual says to adjust the primary air after the main burners have been in operation for 15 minutes; they never are on for longer than 2 to 3 minutes. Is the problem that they are being cut-off prematurely giving rise to somewhat unsteady flickering yellow flame and the rumbling noise at the outset.
Is there something wrong with the S86E - ignition control which may be cutting off the burners early? Or is it the blower speed - with insufficient air passing through the exchange the temperatures rise too fast and the burners are being cut-off. It is 1HP motor and sucking air at such pressure that the bottom panel of the fan compartment is always bowed-in at the bottom. I had the ducts cleaned just a few months ago.
Again my main problem is the rumbling noise at the start of the cycle when the burners come on. My second problem may be the yellow streaks in the flame. This is a 14 year old furnace, 78% efficiency (input 180 Output 136.8). I don't believe the exchanger has ever been cleaned with wire brush etc per the manual. I have just vacuumed.
 
  #4  
Old 02-27-02, 02:36 PM
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My quess

is that air flow is restricted.How long have you resided in your home?Air flow restriction would dictate the over heating and cycling of burners.This may not be the case--but--have gone on jobs before to find an air filter in unit and a plugged air filter in a return duct that customer didn't know existed.YOU COULD remove panel to blower section,tape safety switch so it stays energized---then check and see if unit runs normal.If it does you have an air flow restriction.This would explain bowed panel.Give the forum a holler back to let us know what is going on.PDF
 
  #5  
Old 04-30-02, 04:26 PM
sumarpatel
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Sorry this is late. Went through a number of technicians to resolve the short cycling and the rumbling noise. One company sent somebody who changed the fan-limit switch, but short cyling continued and the next day everything went dead and we had no heat. The same company sent a pair of technicians and after three hours or so said they needed to change 1) the fan-limit switch to a deeper/longer one; the one that was installed the day earlier apparantly was incorrect one, 2) Ignition module and 3) Heat link. The rumbling noise has gone away. But they told me that I needed to add more return air (on the othger side of the furnace) to rid of short cycling.

They have presented me with a large bill.

Questions:
1. I believe that only the heat link needed to be changed to get rid of the rumbling noise. The first technician messed up the wiring and was not very knowledgeable which resulted in him damaging the Ignition module and the fan-limit. Can you please confirm that a bad heat link would create the rumbling noise?

2. Should I add a return duct to the other side of the furnace - this will draw air from a laundry room and an enclosed stairwell that serves all three floors. The house and the furnace are 15 years old and why is it that now there is short cycling and more return air is needed? Is it that existence of shortcycling is a clear indication of need for more return air? It is possible that over the years return air ducts have become blocked.
 
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