Weird Intermittent ignitor

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  #1  
Old 12-23-13, 06:17 PM
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Weird Intermittent ignitor

Hello,
My first post, hello everyone.

My oil furnace burner:
Wesco model X
Suntec pump
Old school Honeywell stack control type KA117A29K--13
2 line system
1A 25A inline filter
Dongan replacement transformer

My Problem / history:
The ignitor is intermittent, some times it works perfect for a couple weeks then it will begin to not light the burner. Failure mode starts with the ignition arc delaying approximately half a second. Of course the furnace rumbles until the excess oil is burned off. After a couple days of this it eventually fails to light the burner and the safety cutout trips.

Diagnostics done:
Checked / reset all the usual stuff like electrodes / pressure / air etc.
Put scope & VOM on the transformer primary leads to check power.
Replaced the ignition transformer with a Dongan LJH-90A

Furnace ran for 2 weeks perfectly then same symptoms again.

Replaced ignition leads.

Furnace ran for 2 more weeks then problem returned.
I tried another Dongan LJH-90A thinking the other one was faulty. With perfect AC 120V to the primary (good waveform on scope) there is a half to a 2 second delay before the arc is established. It does this with the burner disassembled and hooked up so I can watch. Sometimes no arc will establish but I can hear a 60 cycle hum coming from the transformer. The gap is 3/16" but setting it to 1/8" doesn't change the behavior. When I do the standard test with a screwdriver the arc will jump 1.5 inches (when it works).

This one really has me scratching my head. Been fighting it for 2 heating seasons. Sometimes it will run for many weeks before having another "spell."

Any ideas guys?
I consider myself a pretty handy "Mr Fixit" but this has me stumped.

Thanks,
Don
 
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  #2  
Old 12-23-13, 07:04 PM
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Does your control drop out the ignition or is it on all the time?I would make it run all the time with the motor.Change the wire from 4 to 3 in the control.See what it does.They are very touchy though,so breath lightly.Don't know about the short hum,can't sweat everthing. Good luck.
 
  #3  
Old 12-23-13, 10:00 PM
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Hello,
Yes the control drops out the transformer after 30 seconds or so.
What's the benefit of running it full time?

Don
 
  #4  
Old 12-24-13, 07:10 AM
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Hi,the benefit of it running all the time is that it sends a continuos spark to keep the flame/oil ignited. I always changed from the old style transformrs to the newer style electronic style,aas they are 14000 volts. this helps with iginiton problems and unstabel flame problems. try a carlin oil burner lectronic ignitor.41000-41000s. they are not that xpensive and with the extra 4000 volts,it may help keep it running.
 
  #5  
Old 12-24-13, 08:09 AM
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Hi Don & welcome to Do It Yourself.com.
A 1 or 2 second delay certainly shouldn't cause a rumble.
Are the porcelains in good shape? Clean, no cracks, not alligatored (especially where they mount)?

Something else you can do is have a relatively dark area & apply 120 to the transformer. Look for arcing around the base of the insulators. You could have some hairline cracks or carbon allowing some current to leak to ground.
 
  #6  
Old 12-25-13, 02:57 PM
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Hello,
Thanks Grady.
I got a half day to trouble shoot yesterday. I bought an inspection camera so I could look from inside the fire pot at the burner nozzle and electrodes. I saw what appeared to be a carbon thread linking the two electrodes. It fell off when I bumped it with the camera. The burner air is not adjusted rich and carbon does not coating everything like when a nozzle gets fouled. Is it possible that could be what's happening? The carbon thread shorts between and prevents arcing but then burns away or breaks and the arc begins. How does it form? Logic suggests that it would form after shut down and there would have to be residual voltage at the electrodes. I suppose the thread broke off every time I disassembled the burner so I would find nothing upon inspection and the furnace would start normally after.

Unfortunately (or not) after the last inspection yesterday the furnace has been running perfectly. Nice of it to function during the family Christmas gathering.

Question:
Is there a downside to running the ignitor full time like the electrode's or the transformer's life being shortened?

Answers:
Porcelain are clean, electrodes OK and in good shape.

Thanks,

Don
 
  #7  
Old 12-25-13, 03:20 PM
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Excellent work Don. Yes, a carbon thread will indeed cause exactly what is happening to you. How & when they form has long been a subject of speculation.
I've done a number of things in attempts to remendy the situation all of which have been both successful & unsuccessful. The list includes but may not be limited to:
Pulling the electrodes back a bit.
Going to a solid instead of a hollow pattern nozzle
Going to a more narrow spray patterned nozzle

It is also possible there is air blowing back onto the nozzle disrupting the air pattern or the end of the burner is warped. If you have some way to measure draft, in incurments of 0.01" water column, over the fire, measure the draft while the fire is burning but before the fan comes on. Once the fan comes on, if the draft changes (especially moving toward positive pressure) there is a good chance the heat exchanger has failed somewhere.
 
  #8  
Old 12-25-13, 07:58 PM
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WOW, thanks Grady.
I wasn't sure the carbon thread was a valid symptom or cause I suppose. So for grins I reset the electrodes to just .050" in front of the nozzle. I reduced the firing rate by lowering the pressure to 92 psi and readjusting the air. The furnace seemed to like it there. Last year I tried a Delevan .85 / 80* hollow but had trouble with starting and pulsing. I switched to Monarch .85 / 80* NS semi hollow and it fired smooth. A Monarch solid was smokey/sooty. 90* Delevan had ignition trouble and 70* pulsed again. My furnace does not have a draft control damper, should I install one? I've owned the house for 30 years and have only had problems like this in the last couple years. It drove me crazy that everything I had done in the past didn't work. One thing I noticed was the Suntec pump had no poppet valves like the original pump so there was some afterburn especially when the tank was full. I installed a cutoff solenoid in the pressure line to the nozzle. It's controlled by a delay timer so the oil spray starts 1 second after the pump and cuts off immediately when the thermostat opens. All in an attemp to cure this problem. Sure makes for a clean start and shut down. Too bad it didn't stop the problem. :-(

FYI: Last year I tore the furnace down to a naked exposed fire box / heat exchanger. It's made out of heavy gauge steel and showed no signs of trouble. I keep the heat exchanger and flu vacuumed and free of soot for efficiency. My 2400 squ foot house uses ~ 300 gallons per season.
 
  #9  
Old 12-25-13, 08:56 PM
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Grady,
Have been thinking about the formation of the carbon thread. Since the burner will be grounded via the copper fuel lines to the underground tank AND the transformer is connected to the neutral, there is a possibility for a ground potential difference causing the formation of the carbon thread. The furnace is at one end of the house and the AC panel, ground rod and water main are at the other. Also I believe the transformer is center tap grounded.

Just pondering / postulating.
 
  #10  
Old 12-26-13, 03:09 PM
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The transformer is center tap grounded. I don't believe you have an issue with grounding but stranger things have happened. Is the chamber square, cylindrical, or rectangular? If rectangular, aproximate dimensions please. Can you supply me with some pictures of the furnace & burner? Maybe something will jump out at me.

If you have read many of my posts regarding fuel systems, you know how I feel about a two pipe system.
 
  #11  
Old 12-28-13, 11:01 AM
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Hello,
Here is a short video of the furnace behaving properly. Motor/pump & igniter starts, there is a short delay then you hear the solenoid valve open and the flame starts. The igniter shuts off after 20 seconds and you can hear the smooth burn.


Grady: The fire box is cylindrical at 11.5" in diameter. Im firing it at .80 gph currently.

Don
 
  #12  
Old 12-28-13, 02:50 PM
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Something I'd like you to try if you don't mind. Do away with the 2 pipe fuel system. I seriously doubt it's going to do any good but this one has me up against a wall.

Something quicker & easier: Take off just a little air from the burner. In other words, enrich the flame just a bit. Don't go to an orange, smokey fire. From what I could see in the video, the flame looked quite lean for a burner of that vintage.
 
  #13  
Old 12-28-13, 11:05 PM
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Grady,
The furnace has always liked a slightly lean mixture. With it richer it will have trouble when starting up cold after the night set back period. I tried it just now and ended up putting it back where I had it.
I checked into the Tiger Loop system and it looks interesting.
I've not had problems with air or sludge clogging up the filter and lines. I do periodically use my A/C vacuum pump and a jar rigged with fittings to suck the sludge and water out of the bottom of the tank. I never run the furnace immediately after a fill. Traditionally oil prices dip some time in July, if market forces are at work, so the tank has a long time to settle. A little more difficult when oil speculators screw the market up. Last time I filled, the lowest price was in January thanks to a refinery fire.

P.S. The furnace has been running perfectly since Christmas day. :-)

ON EDIT: How far from the nozzle should the swirl vanes (and electrode holders) be? Just for a test I moved it from the halfway point an inch closer which improved the flame shape to my eye.
 

Last edited by Don T; 12-28-13 at 11:26 PM.
  #14  
Old 12-29-13, 01:48 PM
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Couldn't begin to tell you how far the swirl vanes should be from the back of the nozzle. I always measured before doing anything which might move them. Presuming there to be a set screw holding the assembly in place, look for an old dimple in the oil tube.
 
  #15  
Old 12-30-13, 01:12 AM
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Grady,
I can always put the swirl vanes back in their original position. I just figured you are "the guy" so you might know that detail. I have the original furnace installation manual and documents from when the house was built but it doesn't show swirl vanes or give a dimension. Somewhere around here I have a book on oil fired boilers and furnaces written in the 50's. I'll have to find that and read up on it. The furnace is working OK right now so I've buried myself into fixing a 50" Samsung plasma TV. I'm working right next to the furnace room so I can monitor it's cycling. It'll be another week or so before it starts acting up again if it follows the same pattern as before.

I want to thank you for all your help. Stand by, I'm sure I'll be needing assistance again. This problem is so out of the ordinary.
 
  #16  
Old 12-30-13, 02:47 PM
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You, sir, are a man of diverse talents. From working on a 1950's vintage oil burner to a plasma TV is diversity in my book.

On this one, I don't know if I'm "the guy" or not. Blasted intermittent problems will drive you nuts.

Standing By.
 
  #17  
Old 12-31-13, 03:58 PM
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Had a rumbly fire up this AM so it's starting down the path again. I was still in bed so I only heard the rumble through my half groggy sleep.

What do you think about switching to a "flame retention" style of burner? It looks like the end is a separate part.

What do you think of the "Jacobs Ladder" approach to electrode shape & gap?
 

Last edited by Don T; 12-31-13 at 04:28 PM.
  #18  
Old 12-31-13, 04:25 PM
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If you go to a flame retention burner you are going to find it much louder than your present burner. With most burners sold today, one buys the body with motor, pump, & ignition transformer then you buy separately the air tube assembly.

Have you pulled the entire burner? If not, I might suggest doing so in order to inspect the end of the air tube assembly closely. I am wondering if maybe the end is warped or cracked.
 
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Old 12-31-13, 04:30 PM
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I didn't notice anything with the inspection camera BUT no, I have not had the burner assy out in the last 20 years. :-P
 
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Old 12-31-13, 04:54 PM
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If you've not pulled the burner in 20 years, I don't know that I'd suggest doing so for fear the chamber around the end of the burner migh crumble. Instead of pulling the burner, remove the drawer assembly (nozzle tube, electrodes, etc.) & look down the air tube for any inconsistencies around the end. If your arm is small enough, you can reach down the tube & feel around the end.
 
  #21  
Old 12-31-13, 08:13 PM
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Don,
That carbon thread as Grady said is surely enough to stop or delay your spark. All carbon is, is unburned oil.
Burners are made to fire specific nozzles. My guess is your electrodes are getting wet when the burner fires. That's caused from improperly aligned electrodes, a nozzle firing at the wrong angle, wrong spray pattern. Anything that makes the oil hit the tips while firing. Your vanes were set for the right air pattern. Your oil is set at 100 psi for atomization purposes. The better it atomizes the better the burn.

It's OK to change nozzles but remember your burner has limits to how low or high you can fire it.
You mentioned flame retention burner. They have different end cones for different firing rates for just that reason.

If you wanted to try something better you can put in a little smaller nozzle and turn up your pump pressure to about 140psi. There is a cross reference chart for this.

For ex. If your firing 1.00gph @ 100psi, try [email protected] 140. You get much better atomization thus a better burn.

As far as your transformer wiring from 4 to 3 if there is oil getting on the electrodes the constant spark will burn it off the tips while running.
If your pump is getting old the gears might be wearing and you could be getting after drip when the burner shuts down.
Just my opinion but if you can find the book, go back to the factory setting and start fresh.
 
  #22  
Old 01-08-14, 08:19 PM
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Thanks Spott & Grady,
I had a chance to do more inspecting with the camera. Well Grady, it appears you were right about the end of the burner gun being out of shape. It seems small pieces are missing (or just bad casting) and there also appears to be a crack at the 4:00 position (nozzle end view). It looks fine staring down the tube from the fan end however. Looks like I'll be pulling the burner assembly this weekend and checking it out. It had one bad day but has been running ok ever since. It probably explains why it likes a lean mixture.

And the saga continues.............

Don

ON EDIT: I found the book, "Domestic and Commercial Oil Burners" by Charles H. Burkhardt 3rd edition (1969). Really a great read, I had forgotten some stuff so the refresher was needed.
 
  #23  
Old 01-09-14, 07:01 PM
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Keep us up to speed on what is going on.
 
  #24  
Old 01-10-14, 12:08 PM
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Hello,
Here's a couple pics of the air tube assy. Tube opening is 2 - 3/16" in diameter, a cast iron piece which is starting to crystalize with a slightly distorted shape. Actual tube is 4" welded w/.090" wall.
I did some web surfing but only found "retention burner" style replacement tubes.
Might I drag out the TIG welder and refurbish this tube?
What do you think?





ON EDIT: So naturally the crystallization is worse than I thought, it just flies apart when heat is applied so a replacement is in order. What about cutting the cast iron head out and putting a retention head in its place since that seems to be the only thing I can find online? Either that or purchase a 7 - 1/4" long tube assy and cobble that in there since Becket style seems to be the predominant replacement type.
 

Last edited by Don T; 01-10-14 at 02:18 PM.
  #25  
Old 01-10-14, 06:51 PM
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As much as I hate to say it, I'm afraid you are looking at a new burner. A retention head wouldn't work on your burner because it can't develop enough static pressure to make a retention head work. Sorry.
 
  #26  
Old 01-10-14, 08:55 PM
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Hi Grady,
Yeah, bad news.
I figured I had two options; replace the head with one I weld together. About a days work possibly two for about $20 in materials or buy a Becket burner for $500. A third option offered by a local HVAC company was to keep mine going for a while because they are pulling oil furnaces regularly and he would sell me the next used Becket that came in good shape for $200. It would take some adapting/bracket fabricating to get it in there. More efficient though than my "refurbished" tube.

Pondering

EDIT: I reassembled the Wesco and fired it with a Monarch .75 AR at 120 psi. Nice looking fire.................we'll see how it does.
 
  #27  
Old 01-10-14, 09:17 PM
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Two hundred for a good used burner isn't bad, not a super deal but fair. You will likely end up spending some more for an air tube assembly & mavbe a stand. Good luck with the old timer. Hopefully it'll get you thru the winter.
 
  #28  
Old 01-23-14, 06:43 PM
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Wink

Hello All,
My furnace started acting up again so I decided to fabricate a replacement burner combustion head. I just fired it today and all is well so far. The smaller opening has limited the firing to .85 gph. Took me three days of tinkering but what the hey. Another chunk had fallen out of the old head so I just had to..........

Here's the story:
I started with 4" x .083" structural tubing, cut off 3.5" cut and welded it so it would slide into the remaining tube.


Slit the short tube to form a cone,


and checked for true on the lathe.


Fabricated a head face out of 6 gauge steel, welded it all together and turned the assembly true. Hole is 1.8" in diameter.


Welded vanes to the interior to increase the air's angular velocity.


Finished assembly except for drilling the drain hole. You can see my mock-up in paper and plastic.


Inside view
 
  #29  
Old 01-23-14, 06:54 PM
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It will be intresting to see what happens when you fire it up.l
 
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Old 01-23-14, 07:03 PM
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It is running as I type. In fact, it was running when I was working on the post below and is now in it's second cycle (house was cold). So far it's running smooth and quiet. Stack temp is 500*F though. Only dropped 20 degrees compared to the old burner head.
 
  #31  
Old 01-23-14, 07:32 PM
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I don't suppose you have any combustion test equipment do you?
 
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Old 01-23-14, 08:01 PM
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Nope, I'll have to pay the local guy to come out and test it unless I can find someone to barter with.

On EDIT: Sometimes I think I'm loosing it. I just emailed the HVAC instructor at the community college I teach at. We have a full Facilities Maintenance program at PCC. I don't know why I never thought of it before. It will save me some money if I can check out a combustion tester.
 

Last edited by Don T; 01-23-14 at 08:16 PM.
  #33  
Old 01-23-14, 08:32 PM
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Nice job Don,betting mid to low 70's because I know you like it lean.
 
  #34  
Old 01-23-14, 08:40 PM
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Hello,
Ha ha, yeah probably.
Maybe now I can run it a bit richer and my electrodes won't foul. That is how all this got started..............
 
  #35  
Old 01-23-14, 08:52 PM
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My burner is 3450 transformer always on with a little more wack.Never changed electrodes in better then 30 years.There is a change in noise though.Good luck.
 
  #36  
Old 01-24-14, 05:10 PM
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I would be curious to know the results of your tests. If you can lay hands on an comprehensive analyzer it would be great to know: smoke, draft (overfire & at the breech), O2, CO2, CO, & net stack temp. I know, I know, I want too much.
 
  #37  
Old 02-03-14, 04:00 PM
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Hello,
I went though another round of fiddling with the furnace this weekend. I happened onto an efficient setting that really showcased the process of tuning. If I installed a Delavan hollow cone nozzle (.85 gph-80* type A) with the air adjusted to 100% it still had an orange smokey fire, With a Monarch solid cone (.85 gph-80* AR) same problem although the fire was a little less smokey. When I installed a Monarch Semi-hollow (.85 gph-80* NS) I had to turn down the air to 35% to get a proper fire. Stack temp dropped to 460*F. Only problem was it began to pulsate on startup, especially bad in the AM after the night time setback. I figured only a couple things could cause that so I chose to mod the fan for more pressure and if that didn't cure it Id have to do something about the draft. I did not want to usurp the efficiency to get a stable fire (which worked by the way).

Here are the fan mods:
My housing is designed for a 6.5" blower but the one in there is 5.25." I decided to tighten up all the clearances around the blower.

This required fabricating a new "heel" so outlet air cannot bypass to the inlet side. You can see it at the bottom of the housing.


I made a sleeve to tighten the diameter of the inlet side and reach down to the blower.


I also mounted a disc to the motor housing to tighten the tolerance at the back of the blower. In this view you can see it and the end of the "heel" which is angled to prevent the blades from singing.


Another with fan spinning.



This mod cured the pulsating. I can only surmise that the increase in pressure keeps the combustion gasses from blanketing the fire so air remains stable. No luck borrowing the combustion analyzer yet but hoping to test this beast soon.

Don
 
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Old 02-03-14, 08:32 PM
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I must congratulate you on your skills & your dogedness. You, it seems from the pictures & description, have built a higher static burner somewhat similar to the Beckett AFG or Carlin.

Since you are in the expirmental mode, you might want to try adjusting the 'Z' dimention. That is the set back distance from the end of the burner to the nozzle.

It really stinks that you can't borrow some combustion test equipment.
 
  #39  
Old 02-03-14, 11:42 PM
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Hi Grady,
I kinda already went there. During this process I chucked the burner head up and turned the opening to 1.9". I also modified the vanes because the tips intruded too far and I couldn't pull the nozzle back into the tube very far before the vane tips collected drops of oil. I thought I needed a bigger opening because I had to adjust the air to 100% for a .85 gph nozzle. To my surprise increasing the opening made matters worse. That's when I figured out I had an air pattern mismatch. Sometimes I feel like I'm wandering in the dark. Like when I finished the first fan mod and the furnace filled the house with a 875 Hz whine (31 blades X 1725 rpm/60). :-P
 
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Old 02-04-14, 06:33 PM
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I fully understand the wandering in the dark feeling. I'm sure you are going thru the same sort of thing as those at major burner manufacturers have. They had the big advantage of being able to draw on the engineering experience within the whole company & beyond.
 
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