Lennox furnance turns off. Primary Limit switch is open.


  #1  
Old 02-06-08, 07:32 PM
J
Member
Thread Starter
Join Date: Feb 2008
Posts: 4
Upvotes: 0
Received 0 Upvotes on 0 Posts
Unhappy Lennox furnance turns off. Primary Limit switch is open.

My Lenox furnnce turns off by itself. If I reset it, it works for some time (30 min ~ couple of hours) and then goes off. Diagnostic light #1 is flashing while #2 is on. According to schematic diagram this should mean that "Primry/Secondary limit switch is open". Does it mean that the unit is overheating?
Any help is greatly appreciated!
 
  #2  
Old 02-07-08, 09:34 AM
geoimpala's Avatar
Member
Join Date: Jan 2008
Location: canada
Posts: 117
Upvotes: 0
Received 0 Upvotes on 0 Posts
Does the blower run after the furnace heats up at all ? very slowly .. ?


are your filters clean ?
 

Last edited by geoimpala; 02-07-08 at 09:56 AM.
  #3  
Old 02-07-08, 04:28 PM
J
Member
Thread Starter
Join Date: Feb 2008
Posts: 4
Upvotes: 0
Received 0 Upvotes on 0 Posts
Lenox furnance shuts down.

Thank you for reply.
When it comes back up, after power reset, the blower seems to run normally.
When it goes down, the thermostat is showing "Heat On" and the room temperature is lower than the set point.
The filter doesn't look very dirty. At least I remember it in worse condition with no problems.
Thank you.
 

Last edited by jjordan0; 02-07-08 at 05:37 PM.
  #4  
Old 02-19-08, 05:29 AM
S
Member
Join Date: Feb 2008
Posts: 1
Upvotes: 0
Received 0 Upvotes on 0 Posts
I am having the same issue at my work. We have three lennox furnaces and they all have this issue at the same time. They only seem to do it overnight and not on a regular basis. I am wondering if an electrical issue(brown out, surge) could cause this, since it is affecting three furnaces at the same time. The area where I work seems to have bad power, always seems to be surges, making the lights flicker and stuff
 
  #5  
Old 02-19-08, 03:30 PM
Energywise's Avatar
Member
Join Date: Feb 2008
Location: Rochester, New York
Posts: 3
Upvotes: 0
Received 0 Upvotes on 0 Posts
Have you moved any funiture in fron of or on cold air returns? is this a 90% furnace?
 
  #6  
Old 02-19-08, 03:55 PM
E
Banned. Rule And/Or Policy Violation
Join Date: May 2007
Location: Wisconsin
Posts: 7,826
Upvotes: 0
Received 1 Upvote on 1 Post
Originally Posted by sfehrman
The area where I work seems to have bad power, always seems to be surges, making the lights flicker and stuff
It is bad enough diagnosing stuff when there is one issue at hand. They really need to address this issue quoted, first, as this is not right. It could be something as simple as a high amp draw when some big motor kicks in, and the building may need better load balancing done for the building or an electrical upgrade. Or it could be something else involving bad grounds or neutrals or ?.

[You may want to bring this up in the electrical forum here, and go into detail about what you know about your building at work. It may prove to be an interesting thread.]
 
  #7  
Old 02-20-08, 03:14 PM
O
Member
Join Date: Feb 2008
Location: Central Oregon
Posts: 65
Upvotes: 0
Received 0 Upvotes on 0 Posts
If you want to check something that might take some time, turn the breaker off, detach the control board from the furnace, (do not disconnect any wiring unless you know you can connect it back up to the right place) look at the back of the control board and check closely for any burned spots. Any one trace or soldered connection appearing damaged will mean you almost surely have to replace the control board.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: