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Old 07-18-2009, 10:33 AM   #1
cj
 
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Combustion chamber crack? Is this a cleaning port?


I have a older Lennox oil furnace. Attached is a pic of the burner pouch front.
The lower opening (as in pic) has always been covered with cement that has come loose. My question is can I cover this opening with a metal plate (sufficient gauge) or do I have to use furnace cement.

I have also attached a pic of the inner wall of the combustion chamber. It looks like there are hairline cracks developing along the top egde.
Is there anything to prevent it getting worse?
Can I just replace the heat exchanger - it looks like a simple cylinder box bolted inside with ports for flue, flame inspection and burner.

Would appreciate some suggestions and personal experiences.

CJ
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Combustion chamber crack? Is this a cleaning port?-furnace-crack.jpg   Combustion chamber crack? Is this a cleaning port?-furnace-lower-opening.jpg  

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Old 07-19-2009, 10:15 AM   #2
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Combustion chamber crack? Is this a cleaning port?


Hey Pro's out there and weekend warriors. Appreciate some help here. If there is any other info you need, I 'll be glad to provide. Thanks, CJ

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Old 07-19-2009, 10:19 AM   #3
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Combustion chamber crack? Is this a cleaning port?


Post a bigger/backed up pic of the front of the furnace and I may be able to help. Hairline cracks in the chamber are not usually a problem. When it starts flaking off/crumbling etc then it is a problem. Not sure what the bottom port is for but I would use the stove cement. If it ever backfires then the cement will blow off but a plate may cause a pressure buildup/explosion. Our resident oilguy Beenthere must be on holidays. How old is that furnace? Post the model and serial #.
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Old 07-19-2009, 11:37 AM   #4
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Combustion chamber crack? Is this a cleaning port?


Yuri, thanks for the reply.
The furnace is a Lennox OH4-80S. Still get an effeciency of 78-80. The burner is a Beckett. Everything is single stage and the controls - simple and safe.
Have had it serviced every year and the techs have always said it is still good.
I just want to do a better job of cleaning out the soot.

Here's a better pic.

I think the lower port as Yuri suggested is to protect against backfiring. It looks untouched and maybe a drain for any fuel in the combustion chamber bottom . This port actually opens into the bottom of the combustion chamber, looks original and the whole area including the port was filled with loose insulation.
BTW, the burner has never had a backfiring problem. As I mentioned, nozzle has been replaced with every service.
With this in mind - How often should the electrodes be replaced and what are the signs that they are going bad?

Thanks,
CJ
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Combustion chamber crack? Is this a cleaning port?-furnace4.jpg  

Last edited by cjf1980; 07-19-2009 at 11:42 AM.
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Old 07-19-2009, 11:40 AM   #5
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Combustion chamber crack? Is this a cleaning port?


Also can I use a hinged weighted cast iron plate rather than cement, since the cement gives the impression of a patch job for something that is broken.
Infact, that was my impression only to discover that it is an original untouched port.
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Old 07-19-2009, 12:38 PM   #6
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Combustion chamber crack? Is this a cleaning port?


I would use the stove cement. If you have unburned leaking fuel you have a huge fire hazard. As long as the unit is inspected annually and setup properly with a combustion analyzer then you have no worries. Our resident oil guru Beenthere may be back soon with better advice. Electrodes don't fail but the ignition transformer may get weak/weak spark and that can cause delayed ignition. Not sure if the techs have a tester for that but I used to use a large screwdriver and won't tell you how the rest went. Don't touch that chamber or you may damage it, you don't need to try get every particle of soot out, the setup with the combustion analyzer is far more important. Make sure you have 2 newer CO detectors in your house. One in your bedroom. The heat exchangers don't last forever on any furnace and oil can produce CO.

Last edited by yuri; 07-19-2009 at 12:57 PM.
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Old 07-19-2009, 06:31 PM   #7
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Combustion chamber crack? Is this a cleaning port?


Thanks, Yuri for the reply.
I guess we'll just have to wait for BeenThere to return. I was hoping to box it back up today.
Noted your suggestion to use stove cement. Just wondering is that something done during installation? I am trying to gauge if this is the original cement that has come off or something done during a service call before we bought the house. I have had this furnace for 10 years now and had no problem with it. Never any unburned fuel or backfiring. Like I said the loose insulation looks original. Also combustion, CO and the other readings have been good on all service calls this far ( infact the service card hanging from the furnace has the readings for the past 15 years.). I'll have the tech check if the ignition transformer is good. Please let me know if there is a meter/tester for it.

You are right that heat exchangers cannot last forever, which is why I was looking at replacing just that - the heat exchanger. It looks like a replacable part, bolted above the blower with ports that come out of the front panel. Any suggestions on how I can get one for this model.

Also at this point to prevent any more cracking of the chamber, would you suggest a wet pack.... Beenthere has suggested using it in earlier posts to others.

Thanks,
CJ
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Old 07-19-2009, 07:00 PM   #8
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Combustion chamber crack? Is this a cleaning port?


I tried looking up that model # on DaveNet and it must be a VERY old furnace as they have no info for it. Get me the serial # if you can. Or look at the fan housing if it has a date stamped on it. I doubt if the heat exchanger is available. Most of the newer furnaces as far as I know use a fibreglass type combustion chamber. Doesn't look too bad to me. If it ain't broke don't fix it.
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Old 07-23-2009, 09:13 PM   #9
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Combustion chamber crack? Is this a cleaning port?


Thanks for the reply Yuri. Was wondering if BeenThere was back and what his opinion was.
The serial number is "G 121294". This is the only other number on there. The fan has the same model number as on the furnace front panel except with a Z at the end "Oh4-80s-z". There is no date marked.

Any suggestions on using a wet pack for the hair line cracks in the combustion chamber.

Thanks,
CJ
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Old 07-24-2009, 07:01 PM   #10
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Combustion chamber crack? Is this a cleaning port?


He's back just has'nt gone thru all the previous posts I guess. Make a new post if necessary.

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