Weird Intermittent ignitor

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  #81  
Old 02-22-14, 09:31 AM
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Might consider a 60*? You said long chamber. Don't rightly recall but did your burner have that round plate that was a tight fit to the blast tube on the assembly. Good to know you sealed around it after you made your film.
 
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  #82  
Old 02-22-14, 09:35 AM
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Just a little FYI:
I have tested for CO and HC with my automotive emission tester with none detectable. I have also disassembled the furnace down to the heat exchanger to do a visual inspection. It all looked good at the time.
 
  #83  
Old 02-22-14, 02:52 PM
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Hello, I have thought about making a flange for the burner
but the boiler plate wouldn't allow a good seal anyway. This thing has always had asbestos rope type packing around the blast tube. Nowadays I just pack the gap full of thermal insulation. It makes an acceptable seal.

My chamber is round ~11.5" in diameter

By the way, I bought a brick today. I may remove the stack again and fool with baffling at the block plate as Guyold suggests. Just need to do some more tests first to double, no make that triple check the conditions of my tests.

Ok my late lunch is over, time to get back to work on the bathroom.
 

Last edited by Don T; 02-22-14 at 03:47 PM.
  #84  
Old 02-23-14, 01:10 PM
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Hello Experts,
I'm sorry , I don't mean to hog your time BUT.............I have more questions.

I just removed the stack and checked the blocker plate. It does NOT seal off the short route out of the furnace. It has a gap of 1/2" on each side and looks to be manufactured that way. So in other words, not all of the combustion gasses have to circle the heat exchanger. It does look as though the front plate in the upper passage has bowed out and opened the gap. I stuck my flashlight in from the other side to illustrate. View is from the breach / stack connection.



I was thinking I could make a new one to fit tighter. That would sure change the draft characteristics. Still thinking about that brick too.

Questions: Should I make a plate to seal off the short route?
Should it seal 100% or leave a small opening as was intended when built?

View from the other (unused) breach for perspective.
 

Last edited by Don T; 02-23-14 at 01:45 PM.
  #85  
Old 02-23-14, 03:40 PM
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Strangest heat exchanger configuration I've ever seen. That being the case, your guess would be as good as mine. If you are saying one path thru the heat exchanger is longer than the other, I'd block the shortcut.

Don't worry about hogging our time. A puzzler like this is good for the brain cells. Helps to keep 'em from getting lazy.
 
  #86  
Old 02-23-14, 04:21 PM
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Don,
Is that your stack switch I see in the bottom pic. If you completely block that crack will you have enough heat there to activate that bimetal and keep the furnace running without nuisance shutdowns.
You only have 60 seconds before it shuts down.
 
  #87  
Old 02-23-14, 04:45 PM
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Hi Spott,
Yeah, that's the stack control but it's on the "flow" side of the block plate. I can only assume if the installers had used the alternate breach the control would be in the other side.

I've decided to go ahead and clean the heat exchanger since it's apart. There is about a third of it I can not get to easily. Thinking I might find a chimney brush on a flexible handle and send it around the curve. I usually just send the vacuum hose around to pick up the loose stuff but this time there is a crust adhering to the walls and top of the exchanger. I can get 2/3's of it using the barbecue brushes.

Still contemplating the 100% seal of the block plate. It wasn't designed that way and probably for good reason which I will surely find out if I go ahead with it. It gives me pause.
 
  #88  
Old 02-23-14, 05:54 PM
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I think we all trust your judgement Don. Seeing bits and pieces it's hard on this side. You do good work and certainly perk my interest with the old beast.
 
  #89  
Old 02-23-14, 06:22 PM
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Hello Guys,
A FYI post. I put together a crude drawing of the furnace layout.

On Edit: I reworked the drawing after tearing the furnace down and seeing it again.
What looks like a bow in the front plate is actually there by design. They put creases across the panel to stabilize it. Assembly is .080" steel. That means it is in "as designed" condition.

I looked inside the exchanger with my inspection camera and there are baffles and pieces of brick in there. Good call Guyold. There is also buildup in areas I just can't reach to clean.

I made a cleaner tool out of 1/4" copper tubing with HS welding rod brazed to the end to make a 3 pronged scraper, sorta. It helped to get around the corners but I couldn't reach the very back part.



Maybe this will help you visualize my Wesco Furnace.

Thanks guys time to get blackened up to my armpits.
 

Last edited by Don T; 02-23-14 at 09:13 PM. Reason: Edit pic
  #90  
Old 02-23-14, 07:29 PM
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Thinking space there to induce a quicker draft and back-up if the other main side gets plugged up. I seen units piled high with soot. Reminds me I better get to mine this year.
 
  #91  
Old 02-24-14, 02:17 PM
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Good afternoon Guys,
Got the furnace back together at 3 AM this morning. After cleaning the heat exchanger I ended up wedging a brick next to the blocker plate reducing the bypass by 50%. There is a downside, however, the cold start pulsation is back.

Here are the results of the thermal test.
Series 1 is the "norm."
Series 2 is the lean burn
Series 3 is the rich burn
Series 4 was an attempt to get back to the "norm"
Series 5 is with reduced bypass (brick) after cleaning



The register temp shows better thermal rise ending in "normal" temp.

 
  #92  
Old 02-24-14, 04:17 PM
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Hello guys,
I tried a long straight tube with the Dwyer gauge. I know that screws up the absolute measurement but what I was looking for was the relative relationship of the two draft measurements. I stuck the tube all the way in over the fire, moved it around and got the same measurement as I did close to the inspection cover. The over-fire draft was -.005 greater than the stack.

Soooooooooo, I'm still wandering around in the "HUH" mode over that one.
 
  #93  
Old 02-24-14, 04:54 PM
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Don,
I got thinking about your CO & HC analysis. What are the lower detection limits of the instrument? Typically, I would see anywhere from 25-250 ppm of CO on an oil fired furnace.
 
  #94  
Old 02-24-14, 05:07 PM
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Hello,
My Sun emission analyzer has low and high range and can detect down to about 5 ppm CO and HC. In my earlier comment I was testing the plenum for CO and HC with the furnace running double......no make that triple checking for leaks.

I suppose I should test the "exhaust" stack. Duh, that hadn't occurred to me cuz' I figured with a hot chamber there aren't gonna be any unburned HC. I wish I had the later one with a CO2 sensor.
 
  #95  
Old 02-24-14, 05:26 PM
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I'd like to know the CO in the stack.
 
  #96  
Old 02-28-14, 07:25 AM
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Hi Grady,
Looked at my emission tester the smallest scale for CO is .1% or 1000 ppm so it's not too useful I guess. No wonder it read zero.

Don
 
  #97  
Old 02-28-14, 06:23 PM
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1000 PPM would virtually swamp most combustion analyzers. Different ranges for different applications. Something which as always bugged me with much test equipment is instead of displaying < 0.1% or whatever is its lower end of detection, most equipment will show zero. There is no such thing as zero in most cases. If one has the capability, one could count the number of gnats' eyelashes in a cubic mile of air. Counting the number of snowflakes in the air at sea level on the equator is another story. Excuse the rant...pet peeve.
 
  #98  
Old 03-01-14, 09:10 AM
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On the bright side, the furnace has run perfectly this week. No pulsations. I think it's cuz until it's completely cold there is some natural draft during startup. Even when it did it was very short, about a second, then smooth fire. With the cooler stack temps it starts with a -.03 draft and takes 3~4 minutes to reach -.04.
 
  #99  
Old 04-02-14, 11:59 AM
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Hello guys,
Furnace update:
The old timer has been running perfectly and efficiently, only burning 24 gallons in March, thanks to all your help and advice. My wife thanks you, I thank you. This is a great forum, keep it up. Maybe someday I'll feel like enough of an expert at something to contribute and help other members with their problems. In the mean time, I'll keep lurking in the shadows.

Don
 

Last edited by Don T; 04-02-14 at 01:26 PM.
  #100  
Old 04-02-14, 01:46 PM
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Good to hear, Don. Let's hope it just keeps purring along. If you ever manage to lay hands on some combustion test equipment, I'd really like to know the results.
 
  #101  
Old 11-29-15, 01:13 PM
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Checking back in with update

Hello Grady and all,
I just wanted to post an update to satisfy you curiosity.

The furnace burner mods have worked perfectly for all of 2015. I just stuck the tank 11/28/15 and have used only 124 gallons since January. Unbelievable, the lowest usage for any year I have lived here. It was warmer this year but not enough to account for the usage.

I have all of you to thank for the extremely valuable advice I received on this website.

Thank you and have a happy holiday season, stay warm..........

Don T
 
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