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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I Have a Lennox LSS-40 LP gas fireplace. The first time I

Customer Question

I Have a Lennox LSS-40 LP gas fireplace. The first time I light it both burners come on. If I turn it off and back on again in a short time the back burner comes on but the front burner does not come on.
Submitted: 1 year ago.
Category: HVAC
Expert:  Tim H. replied 1 year ago.

Hi, I'm Tim and I'm an HVAC expert here to assist you with your questions. Please provide all information I request as it makes it more difficult to troubleshoot something when I'm not there onsite. Essentially, you become my eyes and ears. Thanks for the opportunity to help. At the end of our dialog, you will have a chance to rate my service, but please wait until we are finished and you're satisfied you have all the information you need.

Sounds like your fireplace and burners are dirty. Best bet is to take the unit apart, remove and blow/wash out the burners and replace. This is the most common cause of the symptom you describe.

Customer: replied 1 year ago.
I have already removed the burners and cleaned them and the orfices. Result is still the same.
Expert:  Tim H. replied 1 year ago.

Then you need to check gas pressure on outlet side of gas valve. Typically this is set to 3.5 inches water column and is measured with a device called a manometer.

Customer: replied 1 year ago.
I have plenty of pressure since the rear burner comes on instantly and has a high flame. I am wondering if it could have to do with the thermocouple. Is there a separate one for each burner?
Expert:  Tim H. replied 1 year ago.


Customer: replied 1 year ago.
No help.
Expert:  Tim H. replied 1 year ago.

You can upload some pictures here, perhaps this will help. If it's a single unit, they would not have multiple thermocouple's to control the pilot. You have to be missing something here. Either the burners are dirty or you don't have them aligned right or the gas pressure's too low. I'd really like to get an actual reading on the pressure rather than just that you believe pressure is OK. But, you'd need to go back over everything. Something's getting missed here.

Customer: replied 1 year ago.
How do I upload pictures?
Expert:  Tim H. replied 1 year ago.

Take a picture, save to your PC and upload using the small paperclip icon at the top of answer box.

Customer: replied 1 year ago.
I give up and will call a repairman.
Expert:  Tim H. replied 1 year ago.

You were going to upload pictures. I never got them.

Customer: replied 1 year ago.
Couldn't get my camera to work.
Expert:  Tim H. replied 1 year ago.

OK, I understand. Well, best of luck to you.