Heat limit or board "you tell me" - http://www.hvacmechanic.com/ Forums

Original message

scot1759

74.132.87.30

"Heat limit or board "you tell me"" , posted Tue 19 Feb 20:01

Ok I have a lennox G24 series furnace. I had the board replaced 2 years ago and it worked great. I have central air and it worked flawlessly this past summer. Now this winter the furnace shuts down in the middle of the night when the temp falls. It does not do it all the time and sometimes stops during the day if really cold out. Now the board was replaced by a certified HVAC Lennox dealor tech. Had another HVAC tech here a couple times still same issue. If I turn the thermostat off then back on it resets and calls for heat. Will sometimes only run through 1 cycle then shuts off. If I turn the stove on and help the warming it will stay running all day. Do I have a bad board again or is the furnace reaching limit and shutting down? My thermostat is digital not mercury however could it be the problem? I believe the flu is clear the light diagnostic when not working is top light solid bottom light flashing. I am lost and tired of flushing money into this piece of crap. $300 a pop for the boards rediculas. Thanks in advance for any help.

Replies:

northernfitter

70.48.185.198

"Re(1):Heat limit or board" , posted Wed 20 Feb 00:12

If your board is showing a lockout then your tstat is not the problem. I can't remember whether or not that board gives a code but check around on the doors and inside top cabinet of furnace for a diagnostic chart. Should give counts of flashes with reason for lockout. If its the spark ignition model there have been some really annoying ignition issues with it sometimes not lighting just because the rubber gasket where the pilot tube comes into the burner box is not sealed up tight or the burner box cover is not installed right. Either way that company should follow up with you for free if there original call did not fix it.

14years as a service tech in Ottawa and the valley. www.reliableheating.ca. For furnace manufacturer ratings go to

http://www.consumerreports.org/cro/appliances/heating-cooling-and-air/gas-furnaces/furnaces-repair-history-205/overview/index.htm?resultPageIndex=1&resultIndex=1&searchTerm=furnace

scot1759

74.132.87.30

"Re(2):Heat limit or board" , posted Wed 20 Feb 12:24

Yes the furnace has a diagnostic light diagram. However the board was replaced and the dilrod that installed the new board did not place the new diagram sticker. The board they replaced it with says "This control board was replaced with a Heatcraft EGC-1" I looked around on the net for heatcraft codes with no luck. I wonder is the original diagram is the same with the new board since it was a Lennox OEM replacement. Here is the diagram sticker:
slow flash-normal operating no call for heat
fast flash-normal operation call for heat
2 flash-system lockout failure to detect or sustain flame
3 flash-presure switch open or closed
4 flash- high limit or rollout switch open
5 flash-flame seized and gas value not engaged
steady on-control board failure

I am stinking however that the code light it shows when it stops working is top light solid bottom light flashing.

marchvac

24.57.149.86

"Re(3):Heat limit or board" , posted Wed 20 Feb 17:33:

Are the led lights both red or is one green. Normally these lights are left and right. So if you look at the filter end to be the bottom which would be flashing the left or right. My scanner is down so I cant send you the details.

Be careful sometimes you don't get a second chance

[this message was edited by marchvac on Thu 21 Feb 20:14]

theduke03

24.250.19.62

"Re(1):Heat limit or board" , posted Tue 19 Feb 20:13

Sounds like a callback to me. Usually free unless you need parts. Just tell them to use the money from the board that you didn't need!

You can't put a price on comfort! Be Safe.

northernfitter

67.68.16.192

"Re(2):Heat limit or board" , posted Fri 22 Feb 16:56

I am guessing from looking at the chart marchvac provided and the codes you are describing that your furnace is cycling on limit for some reason. If I remember right on that furnace the rollouts have to be manually reset and it has worked for you without doing this so that only leaves the on/slow flash related to the high limit.