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-   -   inshot burner flashback? (http://www.houserepairtalk.com/f8/inshot-burner-flashback-8676/)

sadavis80 02-18-2010 09:47 AM

inshot burner flashback?
 
I have an Amana 90% furnace (about 18 years old - 45000 BTU) with dual inshot burners. I have recently bought this home, and suspect that this problem has been there since installation. The furnace seems to heat OK, but the burners (2) often flashback into the interior of the burner. Sometimes it will light properly, but mostly starts up with full flashback burning inside - then will sometimes clear and burn properly. When burning 'correctly', the burners 'pulse' a bit - not bad, but I think the regulator is pulsing the pressure at about 2 per sec pulse. These issues may or may not be related as it doesn't seem to affect the flashback.

I have cleaned and checked everything I can think of. There does not appear to be a crack in the chamber since there is NO change when the blower starts up. Water is properly coming out of the drain and flows out with no problems. The vent flue is clear and the inducer motor blows properly.

The furnace seems to work properly in every way except for the burner flashback. I even tried new burners with the same result. I set up my office in the basement and HEARD the problem - I doubt the previous owners ever noticed it since they didn't "use" the basement routinely.

Anyone got any idea what else to look for ??
tia,
Steve

Wuzzat? 02-18-2010 09:49 AM

maybe it's this
 
'flame rollout" - Google Search

sadavis80 02-18-2010 09:56 AM

There is no flame rollout from the tubes. The flame goes properly into the exchanger tubes regardless of flashback into the burners. I can tell no difference except that the flames are slightly 'yellower' when the burners are in "flashback" mode. No change when the blower comes on.
Steve

Wuzzat? 02-18-2010 10:08 AM

Quote:

Originally Posted by sadavis80 (Post 41064)
the flames are slightly 'yellower' when the burners are in "flashback" mode. No change when the blower comes on.
Steve

???
Check the voltage & current to the gas valve & check for recall notices or Tech. Service Bulletins from Amana.

Can you post a YouTube video?

sadavis80 02-18-2010 11:02 AM

The voltage appears to be fine - don't have an ac ammeter handy and don't know what the current SHOULD be anyway :p. I contacted Amana, but they wont' provide *ANY* information since I'm not a licensed Amana service person (needless to say, I won't be buying any Amana equipment in the future). I did call a local HVAC company - they sent out 2 guys. The guys were unable to find anything wrong, so their answer was to replace the furnace. I have taken it apart about as far as can be done without destroying it - all appears to be normal and in quite good condition considering it's age. I really hate to replace it if there's really something that can be fixed. I've checked the orifice size too. About the only thing that's been done since MFR is a change to LP from Natural gas - but all appears OK there too. Gas pressure checked out OK both in and out of the regulator. I also have a second Amana unit upstairs - it's an 80% unit, but otherwise VERY similar - no problems with it after I cleaned out the flue.
The cover is obviously off now, but it works the same with cover on or off.
Have just taken and uploaded a short video. Kinda dark, but I think it shows the flashback issue and that the flame is otherwise "just fine" ... unless I'm missing something...
The video should be available at
Steve

Wuzzat? 02-18-2010 01:50 PM

Quote:

Originally Posted by sadavis80 (Post 41070)
they wont' provide *ANY* information

The voltage appears to be fine - don't have an ac ammeter handy and don't know what the current SHOULD be anyway

so their answer was to replace the furnace. Steve

Do a web search for Amana product problems. Use the advanced search option and use exact phrases like "class action" or "v. Amana"
Since Auto Repair shops almost never advise buying a new car, I guess I'd look for HVAC places that only do repairs and have no financial interest in selling you a new furnace. Good luck with that search! You could seek out an HVAC consulting engineer.

Voltage is half the story: I'd look for a change in current that coincides with the symptom. Specs on gas valve coils are a State Secret. If it's a 750 mV t'pile you may expect coil currents in the 13 mA range.

My samples of resi. HVAC replacement ages say you have used up 40% of its life, but normal wearout is equal to or longer than replacement age.

I guess I'd get 3 CO detectors and a smoke detector and see what happens.

Re the video, I can only say that a yellow flame means incomplete combustion.

http://www.google.com/search?client=safari&rls=en&q=%22yellow+flame%22+gas+furnace&ie=UTF-8&oe=UTF-8
http://www.google.com/search?hl=en&safe=off&client=safari&rls=en&q=%22yellow+flame%22+gas+furnace+LP+natural&btnG=Search&aq=f&aqi=&oq=
It does seem to be a problem in furnaces.
http://www.google.com/search?hl=en&safe=off&client=safari&rls=en&q=flashback+furnace+burner+patent+resists&aq=f&aqi=&oq=The pdf file of the first patent in this search implies a manufacturer's dilemma between meeting emission standards and having flashback.

From the patent info, and in view of the danger of burner designs that allow flashback, you may want to contact the CPSC about this furnace. I would be surprised if they have not succumbed to
Regulatory capture - Wikipedia, the free encyclopedia
but they may still shame Amana into doing something about this.
Amana may not like you for doing this, but they will certainly respect you.

If you submit a complaint to the CPSC, check after a week to see if it hasn't somehow been "accidentally" deleted from their database.

Today I have learned something that I never would have learned had it not been for your post. Thank you.

If you don't post back, I will assume Amana has sent these guys to your house. . .
http://www.google.com/search?client=safari&rls=en&q=%22flashy+thingy%22&ie=UTF-8&oe=UTF-8:(

sadavis80 02-18-2010 03:05 PM

Quote:

Originally Posted by Wuzzat? (Post 41075)
Today I have learned something that I never would have learned had it not been for your post. Thank you.

I too have learned a LOT about furnaces in general, and specifically a lot more about high efficiency furnaces with inshot burners. However, despite having already researched most of your suggestions, NOT the specific answer to my problem. Going to the CPSC would seem logical, except that the furnace is 20 years old. I wish I really KNEW if it has done this since day one and not JUST since *I* bought the house. I have been known to cause all kinds of previously unknown and subsequently unexplained havoc with things that *I* buy :D.

Looking at online prices to try to replace such things as the regulator - or call ANOTHER HVAC company (all possibly 100% total loss expenditures :eek:), it's getting to the point where it might just make more sense to replace it with a new one - but I sure hate that thought - and so does my bank account.
Thanks for the suggestions.
Steve

Wuzzat? 02-18-2010 03:15 PM

Quote:

Originally Posted by sadavis80 (Post 41077)
Looking at online prices to try to replace such things as the regulator - or call ANOTHER HVAC company (all possibly 100% total loss expenditures :eek:), it's getting to the point where it might just make more sense to replace it with a new one - but I sure hate that thought - and so does my bank account.
Thanks for the suggestions.
Steve

If it's $7K for the installed price of a new furnace [have them first check that your old ducts will work with the new furnace, Manual D]
and a new part is $200,
and you are not paying for labor,
then you should replace the part if the chance of it fixing the problem is at least
100%*$200/$7000 = ~3%.

Sometimes aftermarket parts fix design problems denied by the OEM.


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